Dissertations / Theses on the topic 'Plasticizers'

Plasticizers are additives in poly (vinyl chloride) (PVC) formulations that render the material flexible. This is important for many applications. Because these plasticizers are not bound to the polymer chemically, they will eventually leach out upon disposal. Considering also the widespread use of flexible PVC, it is not surprising that some plasticizers, such as di(2-ethylhexyl) phthalate (DEHP), are considered ubiquitous contaminants in the environment. Previous studies have shown that DEHP, upon degradation, forms stable, toxic metabolites. Because of this and other concerns, DEHP and other phthalates have already been banned in certain products in Canada and other countries. Hence, there is a strong incentive to develop new, green plasticizers. A series of diesters based on maleic acid, which resembles a part of the phthalate chemical structure, was tested, along with other series based on the structural isomer of maleic acid, fumaric acid, and the saturated analogue, succinic acid. The alcohols used to form the ester bonds varied in length from ethanol to octanol and, also, included the branched 2-ethyl hexanol. Each of these diesters was incorporated into unplasticized PVC at about 30 weight-percent and then evaluated for plasticizer properties such as glass transition temperature Tg and tensile strength. These data were compared to each other and to results with DEHP. Pure samples of the diesters were tested for their biodegradability by the common soil bacterium Rhodococcus rhodocrous (ATCC 13808) while it was growing on hexadecane as a primary carbon source. The results demonstrated that esters based on succinic and maleic acids performed at least as well as or were even superior to DEHP as plasticizers. In particular, the esters with the longer alcohols were very good plasticizers. There was little effect due to branching on the plasticizer properties. The experiments with Rhodococcus rhodocrous showed how important the structure of the central diacid is for the rate of biodegradation. In particular, the maleates, which have an orientation of the two ester groups very similar to that in DEHP, showed little to no susceptibility to biodegradation over the course of 30 days. The fumarates exhibited some degradation and the succinates were degraded very quickly. These results indicate that the orientation of the esters in DEHP, is responsible for the stability of this compound in the environment. The other factor in the rate of biodegradation was the length of the alcohol and the longest chains had the slowest rates. However, all straight-chained alcohols were biodegraded without the build-up of stable metabolites. The compounds made with the branched 2-ethyl hexanol did result in the formation of stable metabolites. Consequently, several of the tested diesters could be considered as "green". Yet, in terms of a middle molecule, the succinates should be considered as the best choice. As for side chain length, plasticizer properties improve with increasing alcohol length, and biodegradation properties improve with decreasing alcohol length. A potential candidate for a compromise would thus be dihexyl succinate.
Les plastifiants sont des additifs ajoutés au poly (chlorure de vinyle) (PVC) pour obtenir des plastiques souples; une propriété importante pour plusieurs applications. Ces plastifiants ne forment pas de liens covalents avec la matrice de polymères, ils peuvent donc graduellement migrer hors de celle-ci. Dû à la grande utilisation du PVC souple, il n'est pas étonnant que certains plastifiants, tel le di(2-éthyle hexyl) de phtalate (DEHP), soient considérés comme des polluants omniprésents dans l'environnement. Des études ont démontrées que la biodégradation du DEHP mène à l'accumulation de produits métaboliques toxiques. Ces considérations, entre autres, ont déjà conduit à l'abolition ou à la restriction, au Canada, aux États-Unis et dans l'Union Européenne, de l'utilisation de certains phthalates. Ainsi, il y a un intérêt prononcé pour le développement de nouveaux plastifiants « verts » complètements biodégradables. Une série de composés diesters ayant l'acide maléique comme molécule de base et ressemblant partiellement à la structure chimique des phthalates, a été testée. De même, des séries basées sur l'isomère structurel de l'acide maléique, l'acide fumarique, et son équivalent saturé, l'acide succinique ont aussi été testées. L'estérification des ces acides a été réalisée avec des alcools de longueur variable allant de l'éthanol à l'octanol, incluant aussi le 2-éthyle hexanol. Tous ces diesters ont été incorporés à du PVC à une composition d'environ 30% de la masse du matériau. La température de transition vitreuse (Tg) et la résistance à la traction ont été mesurées pour déterminer l'efficacité de ces plastifiants potentiels. Ces données ont été comparées entre elles ainsi qu'avec des résultats obtenus avec le DEHP. Des échantillons de plastifiants potentiels ont été testés pour déterminer leur biodégradabilité par la bactérie Rhodococcus rhodocrous (ATCC 13808); l'hexadécane étant utilisé comme source principale de carbone. Les résultats obtenus pour les diesters de l'acide succinique et de l'acide maléique ont démontrés qu'ils étaient d'aussi bons ou de meilleurs plastifiants que le DEHP. Dans le groupe des diesters de l'acide succinique, ceux contenant des alcools plus longs étaient de meilleurs plastifiants. Il a été déterminé que la présence d'une chaîne 2-éthyle dans certains diesters avait un effet significatif sur les propriétés des composés. Les expériences de biodégradabilité avec Rhodococcus rhodocrous ont démontré l'importance de la structure chimique de l'acide central des diesters. Les maléates en particulier, dans lesquels la position des deux groupes esters ressemble à celle du DEHP, n'ont démontré aucune susceptibilité à être biodégradés après 30 jours. Les fumarates ont été dégradés partiellement tandis que les succinates l'ont été très rapidement. Ces résultats indiquent que l'orientation des deux groupes esters, comme dans le cas du DEHP, est responsable de la stabilité de ces composés dans l'environnement. L'autre facteur influençant le taux de biodégradation est la longueur des alcools utilisés pour l'estérification: les molécules les plus longues avaient des taux plus bas. Toutefois, tous les alcools sans chaîne secondaire furent dégradés sans accumulation de métabolites stables. Inversement, tous les plastifiants potentiels contenant du 2-éthyle hexanol, ont démontrés une telle accumulation. Plusieurs diesters testés pourraient être considéré comme « verts ». En ce qui a trait au choix de l'acide central, les diesters de l'acide succinique représente probablement le meilleur choix. Pour les alcools utilisés pour l'estérification, les alcools longs démontrent de meilleures propriétés plastifiantes, alors que pour la biodégradation, les alcools courts étaient meilleurs. Un candidat représentant un bon compromis entre ces propriétés est le dihexyl de succinate.

Linear and branched poly(butylene adipate) polyesters with number-average molecular weights ranging from 700 to 10 000 g/mol, and degrees of branching ranging from very low to hyperbranched were solution cast with PVC to study the effects of chemical structure, molecular weight, end-group functionality, and chain architecture on plasticizing efficiency and durability. Miscibility was evaluated by the existence of a single glass transition temperature and a shift of the carbonyl group absorption band. Desirable mechanical properties were achieved in flexible PVC films containing 40 weight-% of polyester plasticizer. Methyl-ester-terminated polyesters with a low degree of branching and an intermediate molecular weight enhanced the plasticizing efficiency, as shown by greater elongation, good miscibility, and reduced surface segregation. A solid-phase extraction method was developed to extract the low molecular weight products that migrated from pure poly(butylene adipate) and PVC/ poly(butylene adipate) films during aging in water. The effects of branching, molecular weight, end-group functionality, and polydispersity on plasticizer permanence were evaluated by quantification of low molecular weight hydrolysis products, weight loss, surface segregation, and the preservation of material properties during aging. A more migration-resistant polymeric plasticizer was obtained by combining a low degree of branching, hydrolysis-protecting end-groups, and higher molecular weight of the polyester. Films plasticized with a slightly branched polyester showed the best durability and preservation of material and mechanical properties during aging. A high degree of branching resulted in partial miscibility with PVC, poor mechanical properties, and low migration resistance. The thermal stability of polyester-plasticized films was higher than that of films containing a low molecular weight plasticizer, and the stabilizing effect increased with increasing plasticizer concentration.
QC 20100805

Glucose, as the most plentiful sugar in nature, is a renewable resource and possesses excellent record in health safety. Levulinic acid is a platform chemical which plays an important role  in  biomass transformation and reactive intermediates. Both glucose and levulinic acid can be produced by biomass conversion with green processing techno logies. Due to the rising needs for bio-based, eco-friendly and non-toxic plasticizers, glucose levulinates as bio­ plasticizers were synthesized from glucose and levulinic acid, by utilizing microwave radiation or conventional condensation reaction (direct-heating method ). Acid number for the reaction liquor was measured by acid-base titration to follow the decrease of acid groups due to the reaction and the trend in  the acid number within reaction time displayed the process of esterification and possible sensitivity of the reaction rate to reaction scale. It showed that microwave radiation had superior ability in  enhancing reaction speed but it was also more sensitive to reaction scale and generated more diverse prod ucts  than the direct-heating method. Besides, the process of reaction and formation  of ester  bonds was  followed  and confirmed by FT IR. The achieved levulinate products were extracted by 2-pro panol and ethyl acetate. The practices showed several serio us problems in 2-propanol extraction, including high dosage required  for  NaCl and solvent and difficulties in purification. The ethyl acetate proved to be a suitable solvent for this study and the  extrac ted  product s  from  the Con-24hrs  and Micro-3/4/5/6/7hrs  were  characterized  by  1H  NMR,  13C N :tvlR. and LDI-MS. The results from spectrum suggested the presence of GL,. and G J .'l. type of levulinates. That means the glucose levulinates were  successfully  synthesized  although  the  dehydration side reaction of glucose was inevitable leading to the generation of glucosidic bonds. In addition, BG (mixture of glucose and glycosidic levulinates) was evaluated by so lution casting of starch and PVC. In order to minimize the microbial contaminations in solution casting of  starch, a  modified  method  was raised and applied. The results showed that 40% BG had goo d miscibility with starch and the conclusion was further proved by DSC measurements, while the BG performed poor miscibility with  PVC.

Earlier work with the dibenzoate plasticizers, di(propylene-glycol) dibenzoate (D(PG)DB) and di(ethylene-glycol) dibenzoate (D(EG)DB), had shown that one yeast could hydrolyze one of the ester bonds of these compounds resulting in an accumulation of the monoesters, di(propylene-glycol) monobenzoate or di(ethylene-glycol) monobenzoate, respectively. These monoesters exhibited an acute toxicity greater than that of the parent compounds and greater than the metabolites of the widely used phthalate and adipate plasticizers.
In the present study, it was shown that the degradation of dibenzoate plasticizers is a common phenomenon among soil microorganisms. In most examples, the degradation was incomplete leading to the accumulation of the expected monoesters. However, the biodegradation of these monoesters was shown to be possible even if the rates of biodegradation were much slower than the rates of hydrolysis of the parent compounds. In addition, it was found that di(ethylene-glycol) monobenzoate was easier to biodegrade than di(propylene-glycol) monobenzoate. This difference was attributed to the methyl substituents on the di(propylene-glycol) monobenzoate. The very fast rates of degradation of simpler benzoate esters such as methyl and ethyl benzoate confirmed that steric effects could be important.
The rate of biodegradation of 1,6-hexanediol dibenzoate was much faster than that of either of the dibenzoate plasticizers. From this, it was hypothesized that the stability of the monoesters of the plasticizers was due to the presence of an ether function. It was also shown that the presence of the monoester of D(PG)DB was shown to increase the rate of hydrolysis of the parent di-ester. This was attributed to the ability of the monoester to enhance the bioavailability di-ester.
Collectively, these results do not support the use of dibenzoate plasticizers as environmentally friendly alternatives to phthalate and adipate plasticizers.

Research was conducted to investigate the effect of chemical functional groups, including the ether function and alkyl branches, on the biodegradation mechanisms and biodegradation rates of dibenzoate plasticizers. Biodegradation of 1,6-hexandiol dibenzoate, a potential green dibenzoate plasticizer, by Rhodococcus rhodochrous, was investigated in the presence of hexadecane as a primary carbon source. The metabolites, produced in the biodegradation process were detected using GC/MS and Fourier transform mass spectroscopy techniques. None of these metabolites were stable, with all tending to biodegrade over the course of the experiments. Biodegradation mechanisms were elucidated for 1,6-hexanediol dibenzoate and two commercial plasticizers, diethylene glycol dibenzoate (D(EG)DB) and dipropylene glycol dibenzoate (D(PG)DB). Biodegradation of all of these plasticizers was initiated by hydrolysis of one ester bond to release a monobenzoate and benzoic acid. It was demonstrated that the diol fragment of 1,6-hexanediol monobenzoate was processed via a β-oxidation pathway, which was not possible for diethylene glycol monobenzoate (D(EG)MB) and dipropylene glycol monobenzoate (D(PG)MB) due to the presence of an ether function in the diols. Thus, accumulation of D(EG)MB and D(PG)MB was observed in the biodegradation broth. The biodegradation of commercial plasticizers, D(EG)DB and D(PG)DB and three alternative plasticizers, 1,3-propanediol dibenzoate, 2,2-methyl-propyl-1,3-propanediol dibenzoate and 1,6-hexanediol dibenzoate, were modeled using a Michaelis-Menten/Monod-type kinetic model. Biodegradation was conducted in an aerated bioreactor using resting cells of Rhodococcus rhodochrous, which had been grown with hexadecane as the primary substrate. Monobenzoates released from the biodegradation of commercial plasticizers degraded slower than the monobenzoates of alternative plasticizers. The rapid biodegradation of monobenzoates released from microbial hydrolysis of alt
Des recherches ont été réalisées pour étudier l'effet des groupes chimiques fonctionnels, y compris la fonction éther et les branches d'alkyle, sur les mécanismes de biodégradation et les taux de biodégradation des plastifiants dibenzoate. La biodégradation du 1,6-dibenzoate hexanediol, un plastifiant dibenzoate potentiel, par Rhodochrous rhodococcus, a été étudiée en présence d'hexadécane comme source de carbone primaire. Les métabolites, produits dans les processus de biodégradation ont été détectés par GC/MS et techniques de spectroscopie de masse à transformée de Fourier. Aucun de ces métabolites ne sont stables, tous avaient une tendance à la dégradation durant les expériences. Les mécanismes de biodégradation ont été élucidés pour le dibenzoate de 1,6-hexanediol et de deux plastifiants commerciaux, le dibenzoate de diéthylène glycol (D(EG)DB) et le dibenzoate dipropylèneglycol (D(PG)DB). La biodégradation de l'ensemble de ces plastifiants a été initié par hydrolyse d'une liaison ester pour libérer un monobenzoate et de l'acide benzoïque. Il a été démontré que le fragment de 1,6-diol monobenzoate hexanediol est généré par une β-oxydation, ce qui n'était pas possible pour le monobenzoate diéthylène glycol (D(EG)MB) et le monobenzoate dipropylèneglycol (D(PG)MB) en raison de la présence d'une fonction éther dans les diols. Ainsi, l'accumulation de D(EG)MB et D(PG)MB a été observée dans le bouillon de biodégradation. La biodégradation des plastifiants commerciaux, D(EG)DB et D(PG)DB et trois plastifiants de remplacement, le dibenzoate de 1,3-propanediol, le dibenzoate de 2,2-méthyl-propyl-1propanediol et le dibenzoate de 1,6-hexanediol, a été modélisée à l'aide d'un modèle cinétique Michaelis-Menten/Monod-type. La biodégradation a été effectuée dans un bioréacteur aéré à l'aide de cellules au repos Rhodochrous rhodococcus, qui avaient été cultivées avec l'hexadécane comme subst

This investigation was focused on the in vitro metabolism of DEHA, DEHP and other common plasticizers by mammalian cell lines. The metabolic products and cell viability of hepatocytes (mouse and human) and human umbilical endothelial cells exposed to plasticizers was investigated in static culture.
Gas chromatography and mass spectrometry showed that all of the plasticizers investigated were partially degraded, but at differing rates, depending on the plasticizer and cell line. Solubility and stearic effects were found to play important roles in determining the rate of hydrolysis. The only metabolic product observed was 2-ethyl hexanol, which accumulated in culture. This was due to the lack of alcohol dehydrogenase production in the human hepatocyte cell line used.
Hepatocyte cell viability was not significantly affected at 4 days of exposure to DEHA. By 12 days, only 50% of the cells remained viable when compared to control experiments. These results suggest that the accumulation of plasticizers metabolites, specifically 2-ethyl hexanol, may have potentially toxic effects.

The degradation of plasticizers by the yeast Rhodotorula rubra J-96-1 (ATCC 9449) was studied in the presence of a water-soluble substrate (glucose). The plasticizers studied included bis 2-ethylhexyl adipate (B(EH)A), dioctyl phthalate (DOP) and terephthalate (DOTP), which are in widespread use. In addition, the degradation of two less common plasticizers, di-propylene glycol dibenzoate (D(PG)DB) and di-ethylene glycol dibenzoate (D(EG)DB), were studied. It has been proposed that the latter plasticizers be used as alternatives to the commonly used plasticizers, which have been associated with negative environmental impacts.
The degradation of D(PG)DB or D(EG)DB led to a significant increase in solution toxicity. This increase in toxicity was associated with the production of metabolites resulting from the incomplete breakdown of the original plasticizers. The metabolites responsible for the acute toxicity in the D(PG)DB system were identified as isomers of di-propylene glycol monobenzoate. A mechanism for the formation of this metabolite was proposed. Although the metabolite observed when D(EG)DB was being degraded was not isolated, it was tentatively identified as di-ethylene glycol monobenzoate by analogy to the D(PG)DB system. This same metabolite was observed when D(EG)DB was degraded by the fungus, Aspergillus niger ATCC 9642-U.
In contrast, there were no observable metabolites nor increases in toxicity in the media during the degradation of B(EH)A, DOP, or DOTP by R. rubra. These observations also differ from those of earlier work in which it was reported that the degradation of all three of these plasticizers by bacteria resulted in the production of toxic metabolites.
Collectively, these results do not support the use of D(PG)DB and D(EG)DB as environmentally safe alternatives to B(EH)A, DOP or DOTP.

Previous studies have shown that the biodegradation of di-ester plasticizers can lead to the accumulation of toxic recalcitrant metabolites. Rhodococcus rhodochrous ATCC 13808 is a bacterium known to degrade plasticizers. The first steps of the biodegradation mechanism consist of esterase-mediated hydrolyses. The present study focused on characterizing the esterase produced by R. rhodochrous and defining its impact on the rate of hydrolysis of different di-ester plasticizers.
By means of esterase activity and growth studies, it was possible to determine that the esterase produced by R. rhodochrous was constitutive and bound to the cell membrane. Treatment with a non-ionic surfactant, Triton X-100, caused solubilization of the enzyme. The esterase exhibited high stability, retaining activity for more than 48 hours, even after separation from the cell. Esterase activity was highest at 30°C but observed at temperatures as low as 4°C.
The comparison of the rates of hydrolysis of different esters showed that the solubility of the substrate had an important impact, with the less soluble compounds generally having lower rates. However, steric hindrance also appeared to play an important role in the determination of the rate of hydrolysis. The most common plasticizer, di(2-ethylhexyl) phthalate, had the slowest rate of hydrolysis. Therefore, given the increasing and widespread use of DEHP and other di-ester plasticizers, such plasticizers will continue to accumulate in the environment. This growing pool of plasticizers will undergo slow biodegradation, resulting in the increasing production of toxic metabolites.

Plasticizers are widely used as additives for the production of PVC and other types of plastics. They have been observed to leach out of the solid matrix over the course of the lifetime of the finished product. These compounds have now been observed across the globe and in different environments. The main focus of this work is the study of the interactions of industrial plasticizers with soil microorganisms including bacteria, yeast and fungi.
This research is concerned with the microbial degradation of plasticizers such as di-2-ethylhexyl phthalate (DEHP) and di-2-ethylhexyl adipate (DEHA). In particular, the study has focused on the stable metabolites produced during biodegradation, including 2-ethylhexanol and 2-ethylhexanoic acid. The first step was to show that these toxic metabolites were found in significant concentrations in the environment. In addition, a series of experiments with a variety of organisms showed how wide spread the ability to produce these metabolites was. Most organisms tested were capable of interacting with the plasticizers and many of these produced the metabolites.
It was apparent that these metabolites could have appreciable stability and an in-depth study with one species of bacteria, R.rhodochrous , showed that the entire initial 2-ethylhexanol component incorporated in the original plasticizers could be accounted for. Some of this was volatile and found in the exit gas of the reactor. This included all of the 2-ethylhexanol and some of the 2-ethylhexanol. These compounds may contribute to the impairment of the quality of indoor air. An overall mass balance showed that while the bacterium could eventually oxidize the 2-ethylhexanol released by hydrolysis to 2-ethylhexanoic acid, it could not degrade this acid. Thus, a summation of the quantities of each of the various metabolites generated equaled the original amount of 2-ethylhexanol in the plasticizer.
A mathematical model was then constructed to include all of the above features of the interaction of R.rhodochrous with the plasticizers DEHA and DEHP. This model included terms for the biological interactions and enzyme kinetics as well as the toxicity and inhibition of bacterial growth by the plasticizers and their metabolites. The increased understanding of the interaction of microbes with plasticizers will lead to a better understanding of the environmental impact of these compounds and their metabolites. The results of this study also demonstrate that when assessing the environmental impact of a compound, it is essential that not only should the impact of the parent compound be considered, but it is essential that the assessment process must also account for impacts associated with degradation products.

Plasticizers are ubiquitous environmental contaminants. Biodegradation of some of these chemicals, such as di(2-ethylhexyl) phthalate (DEHP or DOP), has been shown to lead to the accumulation of toxic metabolic breakdown products. As a result there is a desire to produce new, fully biodegradable, "green" plasticizers. With this goal in mind, a series of tests were developed to be used to measure the plasticizing efficiency of potential green plasticizers. The base resin selected for the study was poly(vinyl chloride) (PVC). The glass transition temperature (Tg) of the plasticized polymer was measured by temperature-modulated differential scanning calorimetry (TMDSC). Tensile tests were carried out on samples of the material from which the tensile strength and the strain at break of the material were measured. The aforementionned properties were measured for PVC plasticized with the commercial plasticizers DEHP, diethylene glycol dibenzoate (DEGDB) and dipropylene glycol dibenzoate (DPGDB) at several plasticizer concentrations.
1,5 pentanediol dibenzoate (PDDB) was synthesized and evaluated as a plasticizer by comparing results for this compound with those for the commercial plasticizers using the developed tests. The depression in Tg and tensile properties were comparable at a fixed composition for blends with PDDB relative to blends with DEHP, DEGDB, and DPGDB. PDDB was subjected to biodegradation unsing co-metabolism by the common soil bacterium Rhodococcus rhodocrous (ATCC 13808). After 16 days of growth, nearly all the PDDB was degraded and only small amounts of transient, unidentified, metabolites were observed in the growth medium during the experiment.

The rheological behaviour of cementitious pastes has been studied by various means. Six different cements have been studied in main parts of the work and all of them have been characterized according to the Rietveld method in order to determine the exact content of minerals. Easily soluble alkalis were measured by plasma-emission- spectroscopy of the fluid filtered from paste. Three types of plasticizers namely naphthalene sulfonate formaldehyde condensate (SNF), lignosulphonate and polyacrylate grafted with polyether (PA) have been used throughout the work. The influence of the plasticizer type on the rheological properties of the cementitious pastes, their adsorption characteristics and their effects on heat of hydration of the pastes has been studied. Limestone has been used as a nonreactive model material for cement in some parts of the work.

All rheological measurements were performed with a parallel plate rheometer. Rather than describing the shear stress-shear rate flow curve with the usual Bingham model resulting in plastic viscosity and yield stress, the area under the curve (Pa/s) was used as a measure of “flow resistance”.

The effect of silica fume and limestone on the rheology of cementitious pastes

The rheological behaviour of cementitious pastes, with the cement being increasingly replaced by densified and untreated silica fume (SF) or limestone was studied. Three plasticizers were investigated namely two types of polyacrylate (PA1 and PA2) and SNF. PA2 proved to be the most efficient plasticizer of the three while PA1 and SNF provided comparable results.

The flow resistance was found to increase with increasing silica fume replacement when SNF and polyacryalte (PA1) were added as plasticizers which was explained by ionization of the silica fume surface and possible bridging with polyvalent cations like calcium. The flow resistance decreased, however, with increasing silica fume replacement when the second and more efficient type of polyacrylate (PA2) was utilized which was believed to occur since the cement pastes were better dispersed by PA2 than SNF and PA1. The silica fume particles could thus pack between the cement grains and displace water. An alternative explanation for reduced flow resistance with increasing silica fume replacement could be a ball-bearing effect of silica spheres.

There was found a trend of increasing gel strength with increasing silica fume replacement of cement even though the pastes seemed to be dispersed by PA2. Cement pastes with densified SF developed lower gel strengths than pastes with untreated SF. This phenomenon was attributed to more grain shaped agglomerates with lower outer surface in densified SF compared to dendritic agglomerated in untreated SF. Decreasing gel strength was found for pastes with increasing limestone filler replacement. Thus silica fume may be advantageous as stabilizing agent for self-compacting concrete preventing segregation upon standing due to a more rapid gel formation.

Effect of cement characteristics on flow resistance

Rheological experiments were performed on pastes prepared from 4 cements originating from the same clinker, but ground to different finenesses (Blaine). The results showed that the flow resistance increased exponentially with increasing Blaine number. No correlations between single cement characteristics such as Blaine, content of C₃A, cubic C₃A (cC₃A) and C₃S with the flow resistance were however found when cements from different clinkers were used. This finding indicates that cement should not be treated as a univariable material. However, the combined cement characteristic (Blaine•{d•cC₃A+[1-d]•C₃S}) was found to correlate with flow resistance, where the factor d represents relative reactivity of C₃A and C₃S. The flow resistance was found to be either a linear or exponential function of the combined cement characteristic depending on plasticizer type and dosage. Correlations were found for a mix of pure cement and cement with fly ash, limestone filler (4%), as well as pastes with constant silica fume dosage when the minerals were determined by XRD.

Influence of cement and plasticizer type on the heat of hydration

The initial heat of hydration peak was measured for the 6 main cements with 0.32% SNF, lignosulphonate and PA2 by cement weight. Correlations were attempted between the maximum heat of hydration rates of the initial peaks with various cement characteristics. The maximum heat of hydration rate seemed to correlate with the product of the cement fineness and C₃A content regardless of plasticizer type. The fly ash cement had to be left out of the correlation plots due to its low initial heat of hydration.

The second, third and fourth hydration peaks were measured on the cement pastes with 0-0.8% SNF, lignosulphonate and PA2 by weight of cement. Lignosulphonate was found to be the strongest retarder while SNF had the least effect on the setting time of the three plasticizers. No correlations could be found between the setting times and cement characteristics such as cement fineness, aluminate and alkali contents for un-plasticized pastes probably because the setting times might have been too close to each other to be able to obtain accurate values. Correlations between setting time and cement characteristics were however found for pastes with plasticizers. The setting times did not correlate with the cement fineness (Blaine) as a single parameter. The product of cement Blaine and C₃A content, however, resulted in a correlation. Furthermore the setting time correlated with the cubic modification of C₃A. It may seem that the setting times depend more on the cubic modification of C₃A than the sum of orthorhombic and cubic aluminate. This finding indicates that the cubic aluminate modification is more reactive than the orthorhombic. The setting time decreased with increasing content of easily soluble K-ions in the cements probably due to the formation of syngenite, K₂SO₄·CaSO₄·H₂O, which removes some sulphate from solution that would otherwise retard C₃A hydration. A similar correlation was not found between the setting time and the sodium equivalent.

Cement interactions with plasticizers

Three plasticizers were studied namely SNF, lignosulphonate and polyacrylate (PA2). PA2 was the most efficient plasticizer of the three tested even thought it was found to adsorb to a lesser extent on cement than SNF and lignosulphonate. SNF and lignosulphonate brought about comparable results.

PA2 was observed to induce flow gain within the 2 hours of rheological measurements which might be caused by the polymer expanding in the water phase and thus improve the dispersion of the paste. Furthermore the grafted side chains of the polymer are considered to be long enough to provide steric dispersion even thought the backbone might be embedded in the hydration products. Cement pastes with SNF and lignosulphonate exhibited flow loss as a function of time which indicates that the plasticizer molecules were consumed by the hydration products.

The concentrations of superplasticizer in the pore water were not found to change markedly in the time range 20-95 min after water addition, indicating that most of the plasticizer molecules were consumed (i.e. adsorbed or intercalated in surface hydration products) within the first 20 minutes after water addition.

The adsorption characteristics were found to depend on the plasticizer type. The adsorption curves of SNF and lignosulphonate reached a plateau at saturation characterizing high-affinity adsorption or increased continuously as a sign of low affinity adsorption. The adsorbed amounts of polyacrylate decreased, however, after saturation had been reached which might indicate that surplus molecules in the water phase compress the ionic double layer or that adsorbed molecules expand and hinder molecules in the water phase to attach at the surface (i.e. osmosis).

The plasticizer saturation dosages were found to depend on cement surface area (Blaine), amount of cubic C₃A and easily soluble sulphates. The saturation dosage of lignosulphonate seemed to have a dependency on the amount of soluble alkali that was somewhat stronger than observed for pastes with SNF. This difference might be caused by lignosulphonate forming complexes with solvated ions in a higher degree than SNF. Moreover alkali sulphates are furthermore often added to commercial SNF based products as the one used in this work. The best correlation, overall, was found for the product of cubic C₃A and Blaine which is logical since high surface and cubic aluminate contents accounts for high cement reactivity and since the plasticizers are known to coordinate with calcium sites. Correlations were also found between saturation dosage with the product of Na_eqv and Blaine as well as the product of Na_eqv and cubic C₃A. The investigations seemed to indicate that the plasticizer saturation concentration increase with increasing alkali content. These findings, however, are rather unclear. According to literature an increased concentration of alkali sulphate in solution results in both an increased hydration rate (which would lead to a higher plasticizer intercalation) and a reduced plasticizer adsorption (due to SO₄^2- - superplasticizer competition). The easily soluble sulphates might, of course, entail the opposing effects of Blaine and C₃A in a way that smoothen the correlation plots of the plasticizer saturation dosage with the cement characteristics.

Effect of temperature on rheology and plasticizer adsorption

Flow resistance and adsorbed amounts of SNF, lignosulphonate and PA2 were measured at temperatures ranging from 11 to 40^oC. Limestone was used as a nonreactive model material for cement. The adsorbed amounts of SNF and lignosulphonate on limestone were found to decrease after reaching a maximum which occurred at approximately 25^oC. Decreased amounts of adsorbed plasticizer with increasing temperature might be explained by increased kinetic energy to the molecules or by an entropy effect. The adsorption of PA2 on limestone seemed to be independent of paste temperature in the range of 16-34^oC which might be caused by low reduction of entropy at adsorption due to its short backbone and long, grafted side chains. The flow resistance of the limestone pastes generally increased with increasing temperature which may be caused by reduced amounts of adsorbed plasticizer and/or dehydration of the paste during the rheological measurements.

Two types of cements were used to study adsorption and flow resistance with increasing temperature namely CEM I 42.5 RR and CEM I 52.5 R-LA. Amounts of plasticizer adsorbed and intercalated (consumed) by cement reached a plateau or even decreased with increasing temperature in the case of SNF and lignosulphonate. This finding might be caused by two opposing effects namely: increased number of adsorption sites due to increased hydration rate with increasing temperature and reduced adsorption due to increased kinetic energy and/or reduced entropy of the plasticizer. Amounts of PA2 consumed by cement increased linearly with increasing temperature as might be explained by the experiments with limestone where the adsorbed amounts of PA2 seemed to be independent of temperature. Increased consumption of plasticizer by the cements with rising temperature is thus probably governed by the increased number of adsorption cites due to increased hydration rate. The flow resistance of CEM I 52.5 R-LA cement increased exponentially with increasing temperature as a function of temperature most likely because of the increased hydration rate. The pastes of CEM I 42.5 RR cement were generally highly viscous and probably agglomerated. The flow resistance reached a plateau value with increasing temperature in this case.

In this thesis, a sustainable and scalable process for modifying the structure of technical lignin to make it suitable for mixing with common bioplastics is studied. More specifically, this project deals with the development of a method of grafting fatty acids onto lignin. First, an updated state of the art concerning the processes for lignin production and its esterification is introduced and thoroughly discussed. Next, the materials and methods used to perform one-pot synthesis on lignin are described. The grafting process is initially optimized using a model reaction; afterwards, these conditions are adapted to technical lignin. The resulting process is also scaled up, overcoming unexpected issues due to mass and energy transfer. The modified lignins have been characterized through various thermal and analytical analyses (such as DSC, TGA and NMR), to provide a detailed description of their properties and structures. Finally, modified lignin was used to produce blends with commercial PLA as a proof of concept. As a matter of fact, this thesis is leading the basis for the fabrication of new-concepts materials based on plasticized lignin, aiming to conjugate sustainable industrially scalable processes and material performances.

Poly(lactic acid) (PLA) is a bio-based, biocompatible, biodegradable polymer that can be produced from renewable resources including starch from corn and potatoes, sugar from beets and sugar cane. Poly(lactic acid) and its copolymers have attracted significant attention in environmental, biomedical, and pharmaceutical applications and as alternatives to petroleum-based polymers. Due to the relatively high glass transition temperature (55°C) and low crystallization rate which respectively result in a brittle behaviour and low production efficiency, the use of a plasticizer is critical to meet technological requirements. Low molecular weight plasticizers show migration issues over time while blending PLA with lower Tg polymers may result in phase separation. Our approach to tackle those issues was to synthetize a novel type of plasticizer containing an oligomeric PLA chain to which a triethyl citrate functionality is grafted as end-chain group. This system guarantees maximum compatibility with the polymeric matrix while still providing an improvement in the material properties. Triethyl citrate (TEC) is a bio-based and biocompatible compound so the “green” properties of PLA are retained. Synthesis and characterization of the plasticizer are described in this research project. The thermal properties of the plasticizers have been investigated using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Upon addition of the plasticizer PLA shows a decrease in the glass transition temperature and an increase in the crystallinity which results in a higher storage modulus.

Earlier work with pure cultures has shown that the interaction of microbes with plasticizers leads to the formation ofmetabolites including 2-ethylhexanol and 2ethylhexanoic acid that resist further degradation. The same studies have shown that these compounds exhibit acute toxicity. This work has shown that the ability of soil micro-organisms to produce these metabolites from the degradation ofplasticizers is a general phenomenon. It was also found that the ability of soil organisms to degrade 2ethylhexanoic acid does not seem to be as common. Taken together, it would be expected that partial de gradation products of plasticizers should be observed in the environment. This was confirmed in a variety of environmental samples including sediments, surface waters, tap water, and fresh precipitation. Thus, even in a complex ecosystem, when plasticizers were degraded, the breakdown is not complete and significant amounts of2-ethylhexanoic acid and 2-ethylhexanol were observed. Since it is already weIl established that plasticizers are ubiquitous in the environment, it is expected that their recalcitrant metabolites will also be ubiquitous. This is a concem because, while the plasticizers do not exhibit acute toxicity, their metabolites do.
Il a été démontré, lors d'études précédentes faites avec des cultures pures, que l'intéraction de microbes avec des plastifiants mène à la formation de certains métabolites résistant à une dégradation ultérieure, incluant le 2-éthylhexanol ainsi que l'acide 2éthylhexanoïque. Ces mêmes études ont aussi démontré que ces composés ont une toxicité aigue. Le présent ouvrage a démontré que l'habileté à produire ces métabolites à partir de la dégradation de plastifiants est un phénomène généralisé chez les microorganismes provenants des sols. Il a aussi été démontré que l 'habileté de ces microorganismes à dégrader l'acide 2-éthylhexanoïque ne semble pas être aussi répandue. À partir de ces observations, il semble que les produits de la dégradation partielle des plastifiants devraient être observables dans l'environnement. Ceci a été confirmé dans un éventail d'échantillons environnementaux incluant des sédiments, des eaux de surface, des eaux potables municipales et des précipitations. Donc même dans un écosystème complexe, lorsque les plastifiants sont dégradés, la décomposition n'est pas complète et des quantités notables d'acide 2-éthylhexanoïque et de 2-éthylhexanol sont observées. Puisqu'il a déjà été établi que les plastifiants sont omniprésents dans l'environnement, il est prévu que leurs métabolites récalcitrants y seront aussi omniprésents. Ceci présente un intérêt majeur puisque ces métabolites, contrairement aux plastifiants, possèdent une toxicité aigue fr

More than one billion pounds of plasticizers are produced each year to supply the plastics industry. Some of these plasticizers, particularly phthalates, are suspected endocrine disruptors. However, few studies have been conducted to determine if they are susceptible to biodegradation by naturally occurring bacteria once they are released into the environment.
Six organisms were tested for their ability to grow in the presence of six different industrial plasticizers. Two bacteria, Rhodococcus rhodochrous and Arthrobacter paraffineus, grew well in media containing n-hexadecane and one of the plasticizers.
Fermentations in a 2-liter reactor were performed with Rhodococcus rhodochrous and three plasticizers: bis 2-ethylhexyl adipate, dioctyl phthalate and dioctyl terephthalate. The organism degraded all of the adipate, half of the terephthalate was degraded and the phthalate was degraded slightly.
In these growth studies, the toxicity of the media increased as the organism grew. This trend was linked to the accumulation of metabolites from the partial degradation of the plasticizer. The two major metabolites were identified as 2-ethyl hexanol and 2-ethyl hexanoic acid. The alcohol was only observed part way through the growth in the presence of the adipate. Its concentration decreased as it was oxidized to the acid and it was not present at the end of the fermentation.
The acid was observed for all three types of plasticizers and it was present in high concentrations at the end of every experiment. The nature and pattern of production of the metabolites were consistent with a pathway for the degradation of all three plasticizers by hydrolysis of the ester bonds.
The accumulation of toxic metabolites indicates that biodegradation may not be a solution to reducing environmental impacts associated with plasticizers that have leached into the environment.

Di-(2-ethylhexyl) adipate, diethylene glycol dibenzoate and dipropylene glycol dibenzoate are commonly used plasticizers, but also known contaminants when they are released into the environment. Studies involving growing the common soil bacterium Rhodococcus rhodochrous and the yeast Rhodotorula rubra in the presence of the plasticizers and an additional carbon source have shown that these compounds are partially degraded, the breakdown products are toxic metabolites and some of them resist further degradation.In order to observe if the degradation pathway and the fate of the metabolites produced are similar in other microorganisms, and if the additional carbon source is needed for the degradation to occur, the plasticizers listed above were added to several different strains of common soil bacteria after they had been grown to the stationary phase and all of the hexadecane provided as a carbon source had been used.It was found that all of the selected bacteria were able to degrade the studied plasticizers, even though there was no additional carbon source available. Degradation was found to be much more extensive in the case of di-(2-ethylhexyl) adipate compared to the dibenzoates. The biodegradation pathway for these compounds was found to be the same as proposed in the previous work using an additional carbon source and the same metabolites were detected. In particular, the most toxic and recalcitrant metabolites (2-ethylhexanol, 2-ethylhexanoic acid, diethylene glycol benzoate and dipropylene glycol benzoate) were observed, and generally, accumulation occurred, although partial degradation was detected in some cases.This work proved that an additional carbon source is not needed for the biodegradation of the chosen plasticizers to happen, and that the biodegradabilities and pathways observed for Rhodococcus rhodochrous and Rhodotorula rubra is extensive to a wider range of common soil bacteria.
L'adipate de di-(2-éthylhexyle), le dibenzoate de diéthylène-glycol et le dibenzoate de dipropylène-glycol sont des plastifiants d'usage commun identifiés comme contaminants environnementaux. Des études de biodégradation de ces plastifiants, effectuées avec la bactérie Rhodococcus rhodochrous et la levure Rhodotorula rubra en présence d'une source additionnelle de carbone, ont montré que ces molécules sont partiellement biodégradés. Cette biodégradation mène à la formation de métabolites toxiques, dont certains sont persistants. L'objectif de cette thèse de maitrise était de déterminer si le mécanisme de biodégradation et la nature des métabolites formés sont transférables à d'autres microorganismes et d'évaluer le rôle de la source additionnelle de carbone dans cette biodégradation. Pour ce faire, les plastifiants mentionnés ci-dessus ont été ajoutés à des cultures pures de différentes bactéries communément présente dans le sol, et ce, lorsque ces cultures ont atteint la phase stationnaire et que la source additionnelle de carbone, l'héxadécane, ait été totalement consommée. L'ensemble des bactéries étudiées a démontré un potentiel de biodégradation des plastifiants testés, et ce, même en absence d'une source additionnelle de carbone. Un niveau plus élevé de biodégradation a été observé dans le cas de l'adipate de (2-éthylhexyle) que dans ceux des dibenzoates. Les mécanismes de biodégradation observés ici en absence d'une source additionnelle de carbone sont comparables à ceux rapportés dans la littérature en présence d'héxadécane. Les métabolites formés étaient également les mêmes et bien que seulement une biodégradation partielle ait été observée, la formation des métabolites les plus récalcitrants et toxiques (2-éthylhexanol, acide 2-éthylhexanoïque, benzoate de diethylène glycol et benzoate de dipropylène glycol) a mené à une certaine accumulation.Cette thèse de maitrise démontre qu'une source additionnelle de carbone n'est pas nécessaire pour que la biodégradation de ces plastifiants ait lieu et que la biodégradabilité ainsi que les mécanismes de biodégradation publiés antérieurement ne sont pas spécifiques aux microorganismes Rhodococcus rhodochrous et Rhodotorula rubra et s'étendent plutôt à divers types commun de bactéries. Ces résultats suggèrent une biodégradation probable de ces plastifiants dans l'environnement.

The processing of polyvinyl chloride (PVC) usually necessitates the addition of compounds called plasticizers to the polymer in order to increase flexibility. These plasticizers, however, are capable of leaching out of the polymer into the environment. This study aimed at characterizing the environmental biodegradation of both commercial and alternative plasticizers. In particular, the effect of surfactants on the biodegradation kinetics was investigated because these compounds are often present in the environment as both waste products and naturally occurring compounds. Since plasticizers are usually hydrophobic, it was hypothesized that surfactants could help biodegradation by decreasing the energy required to bring the plasticizer into the aqueous phase and/or into contact with microorganisms. The addition of surfactants to the biodegradation medium was found to increase the biodegradation rates of the commercial plasticizer di(2-ethylhexyl) adipate (DEHA) and four potential "green" dibenzoate plasticizers. The mechanism of this increase was likely a combination of the emulsification of the plasticizers into the aqueous phase thus making them more available to the bacteria, and also the permeabilization of the cell membranes allowing easier transfer of the plasticizers into the bacteria. The surfactant used in this study did not enhance the biodegradation of the common commercial plasticizer, di(2-ethylhexyl) phthalate (DEHP), which resisted biodegradation under all conditions. Thus, while the presence of surfactants is certainly advantageous to plasticizer biodegradation in some cases, there are still some compounds such as DEHP, which are particularly recalcitrant in the environment.
Le fabrication du polychlorure de vinyle (PVC) nécessite souvent l'addition de composés appelés plastifiants. Cependant, ces composés peuvent être lixivié du plastique et se retrouver dans l'environnement. Le but de l'étude présenté ici était de caractériser la biodégradation de plastifiants industriels et de plastifiants alternatifs, dits «verts». Plus particulièrement, l'effet des surfactants (ou tensioactifs) sur cette biodégradation a été étudié puisque ces composés se retrouvent également dans l'environnement via le rejet de divers déchets ou par des sources d'origine naturelle. Puisque les plastifiants sont généralement hydrophobes, nous supposons que les tensioactifs aident à la biodégradation en diminuant l'énergie nécessaire au transport du plastifiant vers la phase aqueuse, facilitant ainsi le contact avec les micro-organismes. Nous avons démontré que l'ajout de tensioactifs accélére la biodégradation du plastifiant industriel di(2-ethylhexyl) adipate (DEHA) ainsi que celle de quatre plastifiants dibenzoate proposés comme plastifiants alternatifs «verts». Le mécanisme de cette accélération provient probablement d'une combinaison de deux facteurs: la mise en émulsion des plastifiants dans la phase aqueuse, ce qui les rends plus accessibles aux bactéries, ainsi que la perméabilisation des membranes cellulaires facilitant le transfert des plastifiants du milieu extracellulaire vers l'intérieur des cellules bactériennes. Le tensioactif utilisé dans cette étude n'a toutefois pas accéléré la biodégradation d'un plastifiant industriel commun, le di(2-ethylhexyl) phtalate (DEHP), qui a résisté à la biodégradation dans toutes les conditions testées. En conclusion, alors que la présence de tensioactifs peut favoriser la biodégradation des certains plastifiants, certains composés tel que le DEHP, demeurent particulièrement récalcitrant dans l'environnement.

The modification of polymeric materials using plasticizers or elastomers has been investigated in three research programs. The first describes epoxy resins modified with dimethylsiloxane, dimethyl-co-methyltrifluoropropyl siloxane, and dimethyl-co-diphenyl siloxane. The apparent compatibility between the epoxy and the siloxanes was enhanced by increasing methyltrifluoropropyl or diphenyl siloxane content or lowering molecular weight, resulting in profound changes in morphology and the resultant mechanical properties of the modified resins. Fracture toughness was most significantly improved using siloxanes containing at least 40% methyltrifluoropropyl siloxane or 20 and 40% diphenyl siloxane. Comparison of siloxane modifiers with butadiene acrylonitrile modifiers was valuable with regard to both property and morphological effects. The second research project considers the structure-property behavior of polyvinyl chloride (PVC) plasticized with low molecular weight diesters with emphasis on the contrasting effects of different plasticizers on the breadth of PVC's dynamic mechanical spectrum. It was clearly demonstrated that a less soluble plasticizer promoted a greater broadening at intermediate concentrations. Crystallization phenomena and static mechanical properties reflected the greater diluent effect of a more soluble plasticizer. The dynamic mechanical behavior as well as other critical experimental observations were explained using a model which postulates that the network junctions of plasticized PVC consist of "pockets" containing several small crystallites. These pockets are randomly dispersed in a matrix whose homogeneity is governed by the plasticizer's solubility and molar volume. The third research project describes the modification of high 1,4 polybutadiene (PB) with isopropyl azodicarboxylate (IAD) for potential .use as impact modifiers for polar polymers. A method for finding the extent of IAD modification of the PB has been developed using ¹³C nmr and UV spectroscopy. Solution blends of PVC with PB modified with up to 11 mol% IAD were found to be immiscible. Stress-strain testing suggested that IAD modification (11%) enhanced the apparent compatibility between PB and PVC at 25% rubber content. The relatively poor mechanical response of the blends was believed to be related to their somewhat porous morphology.
Ph. D.
incomplete_metadata

Plasticizers are generally added to cosmetic and personal care products to improve the filmforming abilities of the product and increase flexibility of the film formed on the skin or hair surface. For example, plasticizers are present in perfumes to prolong the release of the specific scent, which is the ultimate goal in a good quality perfume. Plasticizers in nail varnishes prevent chipping, improve the aesthetics by adhering to the keratin in the nail which means the coating stays on for much longer, which is the ultimate goal in nail products. Plasticizers improve the gloss, resist chipping and allow quick drying time. Therefore it can be seen that plasticizers play a vital role in personal care products like perfumes and nail varnishes. Certain plasticizers e.g. phthalates, can cause problems associated with human health and can harm the environment. They are easily available and large volumes can be obtained at a low cost. These phthalates, for example, di-butyl phthalate (DBP) have been identified as carcinogenic. Nowadays the occurrence of cancer is rapidly increasing. The plasticizers present in a large number of consumer and personal care products, can possibly be linked to the ever increasing reports of cancer. Therefore a substitute to the traditional phthalate plasticizers must be investigated. The aim of this research is to produce a plasticizer derived from naturally occurring Eucalyptus oil, which can be used to replace the existing plasticizers in cosmetic formulations. Para-menthane-3,8-diol (PMD), occurring naturally in the oil from the tree, Eucalyptus citriodora, forms an acetal with citronellal (PMD, acetal, citronellal all occur naturally in the oil). It has been previously shown that PMD-citronellal acetal will exhibit plasticizing properties similar to conventional plasticizers. The objective was to enhance the formation of the acetal in the Eucalyptus oil by reacting it with excess PMD. An effective synthesis method for the PMD-citronellal acetal enriched oil (~73.8 percent) was determined from optimization experiments. The physical characterisation of the PMD-citronellal acetal enriched oil was done and compared with that of DBP. The acetal-enriched oil had a lower density, slightly higher solubility in water (at 25°C), lower refractive index (Brix percent) and a higher boiling point (350°C) than DBP. The physical characteristics of the Eucalyptus oil source and the acetal-enriched Eucalyptus oil were very similar. This can be expected as the Eucalyptus oil consists of ~84.3 percent Citronellal, ~ 1.3 percent PMD and 2.7 percent PMD-citronellal acetal. In this study the effectiveness of the acetal-enriched Eucalyptus oil (referred to from now on as the bio-plasticizer) was compared to a conventional plasticizer such as di-butyl phthalate (DBP), commonly used in cosmetic products. Two cosmetic formulations were produced: a nail varnish and a perfume formulation. Various tests were performed on these formulations to investigate the plasticizing properties of the bio-plasticizer. The objectives were to determine if the natural plasticizer is as effective as the potentially carcinogenic phthalate plasticizers and can be used as a substitute for the phthalates in personal care products. The results indicate that the bio-plasticizer does behave similarly to di-butyl phthalate, however, the effectiveness of the bio-plasticizer is lower than that of di-butyl phthalate. As the viscosity of the synthesized oil was high, this affected the overall consistency of the products. A more viscous nail varnish and perfume was produced in comparison to the DBP counterpart. The stability of the bio-plasticizer in the cosmetic formulations of nail varnish and perfume was also investigated. The cosmetic products were incubated at 0°C, 25°C and 40°C over a period of two months. Any changes in colour, odour, pH, refractive index, separation and plasticizer peak change in the gas chromatogram trace were recorded. It was determined that the PMD-citronellal acetal-enriched oil was relatively unstable under elevated temperatures and light intensity. Storage under higher temperatures (40°C) tends to increase the acidity. Therefore the bio-plasticizer must be placed in a closed, covered bottle and stored in an environment away from light and elevated temperatures. According to the gas chromatogram peaks, it was clear that both the bio-plasticizer and the DBP were more unstable in the perfume formulation than in the nail polish and were especially sensitive to light when in the perfume. This could possibly be due to the interaction with the fragrance molecule, p-anisaldehyde.

Polymeric materials are strongly entrenched in our society, where PVC is one of the most versatile one. The replacement of traditional phthalates plasticizers, used in the production of soft PVC, has been object of intense research in the last decades, due to their toxicological effects on humans and environmental and the increasing awareness regarding the use of fossil fuels. Bio-based platform chemicals, 5-hydroxymethylfuran (HMF) and 2,5-furandicarboxylic acid (FDCA), accessible from lignocellulosic biomass, have been used in this research as starting materials for the production of alternative furan-based plasticizers. By reduction reaction of HMF, 2,5-bishydroxymethylfuran (BHMF) was obtained and involved in a esterification reaction, which led successfully to the first desired furan-based plasticizer. An esterification acid-catalyzed by Amberlyst-15 on tetrahydrofuran- 2,5-dicarboxylic acid (THFDCA), obtained from FDCA by hydrogenation reaction, gave access to the second promising plasticizer. First investigations of BHMF and 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) etherification reactions were carried out, in order to obtain further substrates that could be used as potential plasticizers.

El argumento fundamental de esta tesis es el estudio de la solvatación iónica por medio de cálculos con ordenador. Tres lineas de investigación han sido seguidas:
(i) Solvatación y mobilidad ionica. Las características principales del processo de intercambio entre la primera y la segunda capa de hidratación iónica para Li+ en agua se ha encontrado ser independiente del estado termodinamico en gran medida. Ha sido demostrado que el desplazamiento cuadrático medio de moléculas pertenecientes a complejos inertes está caracterizado por un largo transitorio debido a la lenta relajación rotacional del complejo. El incremento del coeficiente de difusión iónico debido a los intecambios en la capa de solvatación ha sido calculado por primera vez en el caso de Li+ y Na+. Finalmente, se han derivado leyes de probabilidad que ponen en relación la estereoquímica y la velocidad iónica instantanea.
(ii) Plastificantes. Se propone un nuevo procedimiento para el desarrollo de campos de fuerza intramoleculares, que funciona satisfactoriamente en el caso de dos moleculas de interés en las Batterias a Iones de Litio: carbonato de etileno y -butirolactona. Respecto a la solvatación de Li+ en los dos solventes, el ión está coordenado por 4 moleculas a través del oxigeno del carbonilo con pequeñas distorsiones de la geometría molecular. La nueva asignación de los modos vibracionales hecha para las dos moléculas ha permitido calcular los cambios inducidos por el ión litio, explicando varias caracteristicas de los espectros esperimentales.
(iii) Polarización. Se ha estudiado la eficacia de los metodos de polarización más comunes para simulaciones de Dinámica Molecular en dímeros ión-molécula, usando calculos ab initio como referencia. En lugar de centrarnos en la superficie de energía potencial completa (procedimiento típico), se ha considerado solo la parte electrostática. Se han desarrollado nuevos modelos polarizables para agua y tetracloruro de carbono, que reproducen el comportamiento de sistemas carga-molécula. Ha sido encontrado que, en el caso de dímeros ión-molécula, se requiere una corrección de amortiguamento de la polarización a cortas distancias. El método de los dipolos puntuales junto al método de amortiguamento de Thole reproduce satisfactoriamente las características principales para cationes y aniones atómicos.
The underlying topic of this thesis is the study of ion solvation by means of computer calculations. Three lines of investigation have been followed:
(i) Solvation and Ionic Mobility. The main features of the exchange process between first and second ionic hydration shells for Li+ in water have been found to be largely independent of the thermodynamic state. It has been shown that the mean square displacement of molecules belonging to inert complexes is characterized by a long transient due to the slow rotational relaxation of the complex. The increase of the ionic diffusion coefficient due to solvation shell exchanges has been computed for the first time in the case of Li+ and Na+. Finally, probability laws have been derived which relate the stereochemistry and the instantaneous ionic velocity.
(ii) Plasticizers. A new approach for the development of intramolecular force fields is proposed, which performs satisfactorily in the case of two molecules of interest for Lithium Ion Batteries: ethylene carbonate and -butyrolactone. Concerning the solvation of Li+ in both solvents, it is coordinated by 4 molecules through the carbonyl oxygen with slight distorsions of the molecular geometry. The new vibrational mode assignment performed for both molecules has allowed to compute the vibrational shifts induced by the lithium ion, explaining a number of features present in the experimental spectra.
(iii) Polarization. The performance of the most commonly used polarization methods for Molecular Dynamics simulation is studied for ion-molecule dimers, using ab initio calculations as benchmark. Instead of focusing on the full potential energy surface (the standard approach), only the electrostatic part is considered. New polarizable models have been developed for water and carbon tetrachloride, which reproduce the behaviour of charge-molecule systems. In the case of ion-molecule dimers it has been found that a polarization damping correction is required at short distances. The point dipole method in conjunction with the Thole damping scheme reproduces rather satisfactorily the main features both for atomic cations and anions.

Phthalate esters (PEs) and organophosphate esters (OPEs) are common indoor pollutants frequently detected in environmental (dust, air), personal (hand wipes, diet) and human matrices (urine, serum etc.). In this thesis, mathematical models were used to establish links between intake and body burden for a comprehensive dataset based on a Norwegian study population. Also, the relative importance of different PE uptake pathways was assessed and discussed. Furthermore, the suitability of human nails as an alternative, non-invasive biomonitoring matrix for PEs was investigated. Additionally, information regarding alternative plasticizers to PEs was collected and presented extensively. Results showed that for PEs (paper II), daily intakes based on external exposure media agree with back-calculations using urinary metabolite concentrations, leading to the conclusion that human exposure for the general adult population is well understood and that the most important uptake routes were captured. Overall intake levels are comparable or lower than level presented in recent comprehensive studies and hazard quotients were well below 1 (low risk). As expected, diet was found to be the most important uptake route for all PEs. For lower molecular weight PEs, inhalation becomes a strong contributing pathway whereas for higher molecular weight PEs, dust ingestion was also important. Daily intake based on hand wipes was found to be much lower than the estimated total dermal intake based on air, dust and personal care products, questioning the relevance of hand wipes to represent total dermal exposure. Human nails were found to be unsuitable for replacing urine as a biomonitoring matrix for PEs as internal intake (from blood) cannot explain measured nail concentrations and uptake from air is too slow to reach observed concentrations within a realistic time frame (paper III). Hence, the kinetic links between intake and nail concentrations could not be established. Although exposure to traditional PEs is decreasing, use and body burden of some alternatives are increasing (paper I). Fortunately, most alternative plasticizers have favorable toxicological properties, resulting in low risk for humans. In contrast to PEs, OPEs still remain a group of poorly studied substances in terms of human exposure (paper IV). Due to lack of information regarding human metabolism, reliable links between intake and concentrations in serum and urine could not be established. Modelling results showed that concentrations in serum, and to some extent, urine, were underestimated for 2 compounds. It is likely that a combination of missing intake and suboptimal biomarkers were the cause for this under-prediction. Because of this, further studies regarding human metabolism should be performed for OPEs and potentially more specific biomarkers identified in the future. For PEs, there is a need for more comprehensive datasets to study exposure for high risk groups such as infants and children. Furthermore, dermal uptake remains poorly understood and the uptake of PEs into human nails should be studied in more detail to establish the kinetic links between exposure and body burden.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.

This project studied the biodegradation of a plasticizer, di-(2-ethylhexyl) adipate (DEHA), by two mammalian cell lines, HepG2 and WIF-B, in vitro . An MTT assay showed that DEHA had a toxic effect on both cell lines. Despite this, both hepatocyte cell lines successfully degraded the plasticizer. Metabolites were identified and quantified by gas chromatography. HepG2 cells showed minimal alcohol dehydrogense activity and this resulted in the accumulation of 2-ethylhexanol. WIF-B cells were able to breakdown the alcohol and produced 2-ethylhexanoic acid. It is important to note that an enzyme was essential for this step in the degradation of the plasticizer, as this proves that it was biodegradation and not physical degradation. By comparing the metabolites formed and the order of their appearance, the degradation pathway in these mammalian cells was found to be similar to the established degradation pathways for bacteria, fungi and yeast.

The degradation of common di-ester plasticizers, including di-2-ethylhexyl phthalate, di-2-ethylhexyl adipate and di-(propylene glycol) dibenzoate, by several strains of soil bacteria has been previously shown to lead to an accumulation of metabolites that are more toxic than the parent compounds. This research has shown that the pattern of degradation of these plasticizers can be significantly different in the presence of biosurfactants or synthetic surfactants. In particular, the additions of surfactin, sophorolipid or Pluronic L122 to cultures of Bacillus subtilis each resulted in increases in the quantities of the first metabolites in the plasticizer degradation pathway. One of these was 2-ethylhexanol, which had been previously shown to be the most toxic intermediate released during plasticizer degradation. The other was mono-2-ethylhexyl adipate, the mono-ester released from the hydrolysis of di-2-ethylhexyl adipate. This compound was isolated in this work and found to have a toxicity comparable to that of 2-ethylhexanol.
The cause of the significant accumulation of the first and most toxic plasticizer metabolites in the presence of surfactants was investigated. Results were obtained that suggested that the action of the surfactants was to sequester these initial metabolites. The effect of this would be to reduce the observed rates of subsequent degradation of these two intermediates to less toxic compounds.

Depletion of non-renewable resources and exorbitant levels of carbon dioxide emissions have questioned the further usage of traditional plastics. The imbalance in global sustainability has necessitated the development and use of biodegradable polymers. This research work set sights on understanding the synergistic interactions of plasticizer, starch and Na[superscript]+-montmorillonite (MMT). Having a clear view of the molecular behavior within this ternary system ameliorates the performance of the end product and fabrication of the tailored-property biodegradable polymers. Conversely, the explicit information of the synergistic Interactions of Plasticizers and MMT in hydrophilic starch is still vague. Hence a great degree of work and effort has been put forward through this work to understand the fundamental principles of competitive interaction.The study emphasizes on modelling the kinetics of various components in the system such as crystallisation of the long chain starch, water diffusion from the polymer matrix and the interaction between the MMT molecules and the water molecules. It was observed that the interactions between MMT and plasticiser were enhanced upon increasing the MMT loading. The high hydrophilicity of plasticizer ensured a stronger interaction of plasticizer/MMT which overtook the MMT/MMT interaction causing a dimensional increase in basal spacing in the high plasticiser loading samples.GAB model based on the multi-layer kinetics has been applied in the current work to understand the isotherm behaviour. Small Angle X-ray Scattering (SAXS) was employed to determine the diffraction pattern and intensity of the samples at the micro/nano structural level and thereby fathom the orientation of the crystalline domains. Differential Scanning Calorimetry was carried out to indicate the changes in T[subscript]g/T[subscript]m values of various samples and the corresponding degree of plasticization. The obtained results were then interpreted with Avrami equation to reach solid conclusions.The crystallization ability and intermolecular hydrogen bond strength of the applied plasticizer were the key parameters that affected the crystallisation process. The crystallisation mechanism in xylitol-plasticized samples differed from that of glycerol/sorbitol-plasticized samples. It was also determined that the molecular size of the plasticizer was another significant element that influenced the crystalline domain formation. The interaction process was defined into three stages based on the concentration of plasticizer used. The plasticizer concentration for the formation of a loosen-soft polymeric network and tighten-firm polymeric network was categorised. Correspondingly, the ‘threshold’ value for glycerol, xylitol and sorbitol-plasticized systems was characterised to be 5%, 10% and 5%, respectively. Morphological observations such as Wide Angle X-ray Diffraction (WAXD) and Transmission electron microscopy (TEM) has been utilised to examine the morphology formed in all nanocomposite samples.A relatively unsaturated loosen-soft polymeric network was formed and the starch/plasticizer interaction and starch/MMT interaction transpired without interfering each other within the threshold limits. Nonetheless, beyond the threshold, a relatively saturated tighten-firm polymeric network was observed as confirmed by x-ray scattering results, the molecular dynamic modelling results and Positron Annihilation Lifetime Spectroscopy (PALS) measurements from representative samples. Plasticizer/plasticizer interactions significantly altered the MMT exfoliation process and crystallization behaviour of the corresponding sample.The complex interactions existing in the polymeric system were found to be dependent on several main factors including type of the plasticizer and the relative ratio of plasticizer and MMT. These factors have been kept in mind whilst designing the modes of experiment and understanding the related outcomes. The incidence of excess moisture successfully modified the interactions amongst starch/ MMT/plasticizer. Water molecules behaved like a typical plasticizer and occupied most of the small voids between the starch polymers throughout the polymeric network.

Poly(vinyl chloride) (PVC) requires the addition of large quantities of plasticizers in order to improve the flexibility and processability of the polymer. Since the plasticizer is not bound to the PVC polymer matrix, there is a tendency of the plasticizer to migrate into the surroundings. The most commonly used PVC plasticizer, di-2-ethylhexyl phthalate (DEHP), has become a ubiquitous environmental contaminant. As with other plasticizers, it may either accumulate or lead to the formation of metabolites, which resist further degradation and can themselves be toxic. Accordingly, there is incentive for the development of a 'green' plasticizer as a replacement to DEHP in order to minimize the environmental impact of PVC production and use. In this study, a method was developed to quantify the degradation of plasticizers used in PVC formulation or proposed as alternatives. The method is based on derivatization in order to lower the boiling points of the compounds and allow for analysis by gas chromatography (GC). Using this developed method, the biodegradation of two different families of potential 'green' plasticizers was considered. The biodegradation was assessed using Rhodococcus rhodochrous and evaluated based on the rate and completeness as well as the toxicity and stability of any observed metabolites. It was found that the poly([ε]-caprolactone)-based plasticizers containing octanoate-terminal groups degraded much more rapidly and completely than the benzoate-terminated ones. Furthermore, no metabolites were observed during the degradation of octanoate-terminated plasticizers while the benzoate-terminated plasticizers gave rise to metabolites which contributed substantial toxicity to the culture media. Under ideal conditions, these metabolites were shown to be biodegraded themselves. The methodology and data presented in this thesis can be used as a tool in selecting a 'green' plasticizer based on the degradation criteria, and aid in the selection of alternative plasticizers to DEHP.
Le polychlorure de vinyle (PVC) requiert l'ajout important de plastifiant afin d'obtenir un polymère flexible et plus facile à mettre en forme. Comme ces plastifiants ne sont pas chimiquement liés à la matrice, ils ont toutefois tendance à migrer dans le milieu environnant. Le phtalate de diéthylhéxyle (DEHP) est le plastifiant le plus couramment utilisé et est maintenant un contaminant omniprésent. Tout comme d'autres plastifiants, il peut s'accumuler dans l'environnement ou se biodégrader et former des métabolites qui peuvent résister à la biodégradation et être potentiellement toxiques. Cette situation inquiétante a susciter l'intérêt envers le développement de plastifiants verts offrant une alternative au DEHP et permettant de minimiser l'impact environnemental de la production et de l'utilisation du PVC.Dans le cadre de l'étude présentée dans cette thèse, une méthodologie a été développée afin de permettre la quantification et le suivi de la biodégradation de plastifiants utilisé pour le PVC ou proposés comme alternatives. Cette méthode basée sur le dérivatisation permet la diminution du point d'ébullition des composés et l'analyse par chromatographie en phase gazeuse (GC). Cette méthode a été utilisée ici afin d'étudier la biodégradation de deux familles de composés proposés comme plastifiants verts. La biodégradation a été étudiée à l'aide de la bactérie Rhodococcus rhodochrous et évaluée en fonction de la cinétique et l'étendue de la dégradation ainsi que selon la formation de métabolites et la toxicité résiduelle. Les résultats ont démontré que les plastifiants à base de poly([ε]-caprolactone ayant des groupes terminaux octanoïque se biodégradent plus rapidement et que ceux ayant des groupes terminaux benzoïque. De plus, aucun métabolite n'a été détecté lors de la dégradation des plastifiants octanoïque alors que les plastifiants benzoïques ont formés des métabolites et engendré une toxicité résiduelle du milieu de culture. Dans des conditions idéales de biodégradation, les métabolites se sont dégradés. La méthodologie développée et les résultats présentés dans cette thèse seront utiles à la sélection de plastifiants verts offrant une alternative au DEHP.

PVC accounts for more than 25% of the plastics used in medical devices, with medical tubing, such as that used in catheters and endotraechal the major applications. PVC is often plasticized using phthalate esters, but this group of plasticizers is environmentally contentious and there is evidence to suggest they are dangerous to human health. Furthermore, medical device-related infections and biofilm formation have been major challenges associated with PVC medical devices. Therefore, a dual functional novel additive having both plasticizing and antimicrobial properties could be a solution to address these problems. Two ionic liquids(ILs, organic liquid salts in room temperature), l-ethylpyridiniurn docusate(IL 1) and tributyJ(2-hydroxyethyl)phosphonium docusate(IL2), were designed and synthesized in the hope they would act as both plasticizer and antimicrobial agent for PVc. The plasticization of these composites was assessed based on a reduction in the glass transition temperature(T g), determined from dynamic mechanical thermal analysis(DMTA), changes in torque data during processing, and static mechanical tensile tests. The antimicrobial efficacy of the ILs and their precursors were evaluated with time-kill assay. The antimicrobial activity of PVC-IL composites were assessed by disc diffusion tests, biofilm formation tests, and examination of biofilm growth on PVC samples using scanning electron microscopy(SEM). The leaching of ILs from PVC was also examined from leaching tests, via a combination of gravimetric measurements, UV - Vis spectrophotometry, FTIR-ATR and DMTA. The results indicated that both ILs exhibited a plasticizing effect on both sets of PVC formulations manifest by reduction in Tg, storage modulus, and torque during processing, but enhanced flexibility measured by increased elongation at break from static tensile tests was only observed for the rigid PVC-IL2 samples. Both ILs, both rigid PVC-IL samples and non-rigid PVC-ILl samples were antimicrobially active against most Gram-positive bacteria, and displayed excellent antibiofilm forming properties. Overall, IL2 was a better plasticizer for PVC than IL 1, and IL 1 was a better antimicrobial agent than IL2. The enhanced antimicrobial effectiveness of IL 1 was related to the greater release of IL 1 from the PVC matrix, observed during leaching tests, and increased surface hydrophilicity, evident from contact angle measurements. FTIR-ATR studies on PVC-IL samples during leaching tests revealed a potential interaction between the docusate anion with the surrounding immersant(PBS). The effect of PVC molecular weight on the release behaviour of ILs was also evident from leaching tests carried out on non-rigid PVC-IL samples containing PVC resins with different molecular weight. The addition of these ILs to PVC also reduced the thermal stability of both rigid and non-rigid PVC. Comparing both ILs with conventional PVC plasticizer, di- octylphthalate(DOP) in both PVC formulations, it was found that although DOP has a slightly higher plasticizing efficiency, the ILs have the advantage of dual functionality, as both plasticizers and antimicrobial agents.

Many products used in our everyday life contain chemicals added to give them specific properties. Flame retardants (FRs) are added to prevent or retard fires in textiles, plastics etc., while plasticizers are supplied to make plastics more flexible. Through their widespread applications chemicals from both groups are emitted and spread in the environment during usage and disposal. For a long time these products were mainly disposed of in landfills, and in many areas they still are. Thus, since some of these chemicals also pose potential environmental risks and health hazards, there is a need to elucidate their fates during exposure to the landfill environmentThe objectives of this thesis were to investigate the leaching and transformation of FRs and plasticizers from products in which they are used under simulated landfill conditions. To assess the importance of changes in these processes as landfills progress through recognised ageing phases (accompanied by large transitions in both physico-chemical and biological conditions) it was desirable to simulate the changes that typically occur in landfills within a short time period, of 1-2 years.. This was achieved using the newly developed intermediate-scale (3 litre) Modular Environmental Test System (METS).The METS were employed in two studies. The first was an investigation of the leaching and degradation of plasticizers from PVC carpet material incubated at different temperatures (20, 37, 55 and 70°C) prevailing in landfills. Plasticizers subjected to this investigation were the phthalates di-2-ethylhexyl phthalate (DEHP) and benzyl-butyl phthalate (BBP), both of which were found to leach from the carpet. The leaching of DEHP and BBP generally increased with increases in the incubation temperature. However, the most rapid leaching of BBP occurred at 37°C, probably due to high microbial activity at this temperature. Both DEHP and BBP were shown to be degraded within the landfill environment and the degradation potential was highest during the methanogenic landfill phase. In the second METS study the leaching of FRs used in both reactive and additive applications (i.e. chemically bonded to and merely blended with the material, respectively) was characterised. The epoxy oligomer tetrabromobishpenol A (TBBPA) and the phosphorus-based Pyrovatex FRs were selected as representatives for the reactive FRs, while the nitrogen-based melamine and phosphorus-based Proban FRs were selected to represent additive classes. During the incubations, which lasted more than two years, the leaching from melamine was shown to be affected by the landfill phase development. The leaching from the Pyrovatex-treated material and the TBBPA epoxy oligomer seemed to result almost entirely from the washout of unreacted manufacturing residuals. This was also probably true for the FR in the Proban-treated material, although it is durable (despite being additively applied) and thus seemed to leach more slowly (manifested as an increase in phosphate levels in the leachate towards the end of the monitoring period).Finally, due to the paucity of knowledge regarding the fate of ether derivatives of TBBPA (which are also used as FRs) an anaerobic degradation assay was performed. The method employed for this assay was a modified, small-scale ISO standard method. In order to evaluate the degradation assay a uniform analytical protocol was developed. The degradation survey showed that losses of TBBPA, TBBPA-dimethyl ether and bisphenol A dimethyl ether occurred, but no losses of the most hydrophobic compound, TBBPA-dibromopropyl ether, were observed.
Många av de varor och produkter vi kommer i kontakt med dagligen innehåller kemikalier, som tillsats för att materialen i produkterna skall få specifika egenskaper. Till dessa sk funktionella kemiska föreningar hör till exempel flamskyddsmedel och mjukgörare. Den förra förhindrar att produkter fattar eld eller minskar omfattningen av brand. Mjukgörare ingår fr a i plaster för att dessa skall bli smidiga och formbara. Eftersom stora mängder av dessa substanser används eller har använts i produkter i samhället har de spridits till många miljöer. Produkterna hamnar ofta på soptipp, då de inte används mer eller är utnötta. Eftersom flera av dessa substanser innebär risk för hälsa och miljö, är det påkallat att utreda hur de beter sig i soptippsmiljön.Syftet med detta avhandlingsarbete är att undersöka eventuell frisättning och omvandling av dessa två typer av funktionella kemikalier i deponimiljö. Sedan tidigare vet man att sådan frisättning kan var starkt kopplad till åldern och därmed utvecklingen av den kemiska och fysiska miljön förändrats fr a genom tillväxten av mikroorganismer i soptippen. För att komma åt att studera frisättningen under de för deponier karakteristiska utvecklingsfaserna utvecklades en metod (Modualr Environmetal Test System; METS) för att simulera faserna över relativt kort tid (ca 1-2 år). I avhandlingen presenteras två studier, där METS utnyttjats: 1) Frisättning av mjukgörare från en PVC-matta i relation till temperaturer, som uppträder i soptippar (20-70oC) samt 2) Läckage av olika flamskyddsmedel i reaktiv respektive additiv användning studerades för olika applikationer. Vid reaktive applikation är flamskyddsmedlet kovalent bundet till polymeren i produktmaterialet, medan det additivt använda flamskyddsmedlet är inblandat i materialet.Två ftalater (di-2-etylhexyl ftalat, DEHP och bensyl-butyl ftalat (BBP), visade sig läcka från mattan, vilket ökade med högre temperature. De frisattes dock som mest vid 37oC, vilket sannolikt beror på den höga mikrobiella aktiviteten vid denna temperatur. Båda ftalterna bröts ned i soptippsmiljön och hastigheten var störst i den metanogena fasen.En epoxyoligomer (tetrabromobishpenol A TBBPA) och Pyrovatex, som bygger på en fosforförening, användes som modeller för reaktiva flamskyddsmedel. Melamin, som klassas som ett kvävebaserat flamskyddsmedel, fick tillsammans med Proban (fosforbaserat) represen-tera de som används additivt. Medan en frisättning av melamin kunde relateras till utvecklingen av deponimiljön simulerad i METS, så verkar den observerade frisättningen av kemikalierna från de reaktivt behandlade Pyrovatexmaterialet och från epoxipolymeren TBBPA förr ha en fysikalisk-kemisk grund oberoende av utvecklingsfaserna i tippmodel-lerna. Flamskyddsmedlen tvättades helt enkelt ut ur de behandlade produkterna. Probanbehandlingen, som motstår förhållandevis många tvättar trots att det används additivt, visade sig läcka långsamt utan en direkt koppling till fasutvecklingen i METS.Kunskaperna om vad som händer med TBBPA:s eterderivat i deponier är i stort sett obefintliga. Flera av dessa derivat används också som flamskyddsmedel. Därför genomfördes en anaerob nedbrytningsstudie av dessa substanser. För att kunna göra denna studie behövdes en omfattande anpassning och utveckling av metodik, vilket resulterade i ett nytt protokoll för analys av dessa ämnen i olika matriser. Studien visade minskning av koncentrationerna av TBBPA, TBBPA-dimetyleter och bisfenol A dimetyl eter, vilket kan tas som ett tecken på att en transformation och/eller nedbrytning skett. Då dessa föreningar kan omvandlas till mer toxiska substanser bör de undersökas vidare.

Competitive adsorption of poly(vinyl alcohol) (PVOH) and plasticizers (PEG Mw 600 and 2000, M600 and quaternized M600) onto Na-bentonite has been studied. Preliminary experiments showed that as the concentration of plasticizers or PVOH increased, the amount adsorbed by clay increased and followed a Langmuir-type adsorption. The order of affinity to clay was PVOH, PEG2000, M600 and PEG600. Step changes occurred in the gallery with increasing amounts of plasticizer offered as it expanded from a depleted single layer through to a full single layer, then a combined single and bilayer system, and finally a full bilayer system. For PVOH, multi-layers were observed, as well as mostly exfoliated structures when the PVOH concentration was > 75 wt%. The extent of change in the d-spacings of PEG600/clay and PVOH/clay systems were shown to be greatly affected by thermal treatment and exposure to different relative humidities at low organic loadings (23 wt%). The thermal stability of PEG600 or PVOH in clay was dependant on the loading and so related to the type of structure. Desorption of organic from clay by washing up to ten times with water showed that not all organic was removed since the d-spacing of organic/clay did not collapsed to that of clay alone. In the competitive adsorption studies, both plasticizers (PEG600 or M600) and PVOH were present within the clay gallery, the amounts of plasticizer and PVOH present increased with the amount of plasticizer and PVOH offered. The amount of PVOH adsorbed by clay was slightly increased by the presence of 1-30pph PEG600, but reduced in the presence of 30 pph M600 and 1, 10 and 30 pph QM600, whilst the amount of PEG600 or M600 adsorbed by clay was reduced when the amount of PVOH offered was increased. Samples prepared by mixing PEG600 with clay first before adding PVOH consistently exhibited slightly higher d[001]-spacings and peak intensities when compared to the corresponding samples prepared by either mixing PEG600 and PVOH before adding clay or mixing PVOH with clay first before adding PEG600. The differences are assigned to their molecular arrangements rather than quantities adsorbed. The tensile storage modulus, &, alpha temperature and E[a] of PVOH/clay systems increased as the amount of clay increased whilst the opposed trend was observed for the toughness and damping properties. Introduction of clay into PVOH resulted in a reduced water permeability in the nanocomposites since an 8 times reduction was observed when clay content was 50 wt%. The opposite trend was observed when 20 wt% PEG600 was introduced to the PVOH since it increased the water permeability by 4.4 times. Introduction of clay to PVOH/PEG600 reduced the water permeability and -23 wt% clay was needed to return the WVTR value to that of PVOH alone. Besides clay, the crystallinity of PVOH was shown to reduce the water permeability of the nanocomposites. The levels of PVOH crystallinity were identified using FTIR from the intensity ratio of the bands at 1142 cm[-1] and 2942 cm[-1]; the ratio increased with heating temperature and clay content but decreased with time when exposed to 85% relative humidity. In addition, the intensity of the XRD peak at ≈ 19 °20, which relates to PVOH crystallinity increased with temperature and decreased with exposure time for all films. The sample crystallinity was greatly affected by water content, however, the induced crystallinity was not completely lost after being maintained at 23 °C and 85 % RH for 51 days.

Plasticizers are often interchanged with the idea that they will not affect the processing behavior of Polyvinyl Chloride (PVC). However, when the plasticizer type is changed, various complaints are made by the processors that the material no longer processes the same. This research was concerned with the effect of three different plasticizers on the plasticating extrusion behavior of PVC. Di-isodecyl pthalate (DIDP), di-hexyl pthalate (DHP) and 2-ethyl hexyl pthalate (DOP) are the three plasticizers used in this study. First some differences in the extrusion performance of the three differently plasticized PVC compounds were identified. In particular, it was observed that pressure build-up, flow rate and power requirement were affected by the plasticizer type with the DIDP plasticized materials generating higher pressures and requiring more power than the other two plasticized materials. The differences in extrusion characteristics have been observed for two different dies (1/8 and 1/16 inch diameter) attached to the extruder. The differences were most significant between the DIDP and the DHP plasticized mixes. Factors which could influence the processing behavior of plasticized PVC include viscosity, compaction, thermal conductivity, specific heat, and friction coefficient. It was found that all other properties other than the viscosity were unaffected by the plasticizer type. On the other hand, viscosities were significantly affected by the plasticizer type with the DIDP plasticized materials displaying higher values between 160 and 190 °C. The difference in viscosity was larger between the DIDP and DHP plasticized materials than between DIDP and DOP plasticized materials. The differences in viscosity between DIDP and DOP plasticized materials tend to diminish considerably at 190 °C. Two flow regions characterized by different degrees of fusion above and below 165 °C were identified for the plasticized PVC compounds. Plasticized PVC exhibited yield stresses with the DIDP plasticized materials having higher values. The yield stresses were responsible for the significant difference in viscosity at lower shear rates. The yield stress was a more dominant feature at temperatures below 160 °C and this fact was made use of in modeling the solids conveying zone as a fluid with yield stress. Correlation was established between the viscosities and the extrusion behavior of the plasticized PVC compounds. It was observed that the DIDP plasticized mixes had higher viscosities, fused earlier in the screw channel, gave rise to higher pressures, required more power and in general exhibited higher flow rates at the same screw speed. The finite element method was used for the numerical simulations. Based on the experimental results, the numerical modeling of the melt zone was performed in order to predict the differences in the extrusion characteristics. The melt zones were modeled as a temperature dependent power law fluid having two different viscosity expressions above and below 165 °C. The numerical predictions for pressures and flow rates in the extruder with the 1/8 inch diameter die were in good agreement with the experimental results. For the case of the 1/16 inch diameter die attached to the extruder, the numerical and experimental flow rates were in good agreement but the pressure predictions, although indicating the correct trends, were off by 15 to 20% from the experimental results. In general the differences in the physical properties, viz. viscosities, were used to predict the differences in the pressure build-ups and flow rates. Also the solid conveying zone was modeled using a Herschel Bulkley model. It was possible to match the experimental and numerical results for the solids conveying zone by using an average density value for the entire solids conveying zone, but more work needs to be done in order to establish greater validity and applicability of this model.
Ph. D.

Thin layered systems can be considered as a solution to the repair and protection of concrete structures. This subject was studied in the current investigation. Some common uses of these systems include protection, upgrading and rehabilitation of the floor slabs,restoration of appearance of the structures, impermeability, skid resistance, wear resistance, and protection of the reinforcing steel of concrete structures against atmospheric or chemical attack. However it can be said that protection, upgrading and rehabilitation of floor slabs are the main uses for the design of modem thin layered systems. For example a thin layer of a polymer concrete with a thickness of less than 3 nun can resist a very highly concentrated load resulting from a steel wheel rolling load of 5000 N without any sign of defect. Thin layer systems therefore include traditional screeds, externally bonded steel plates, plasters and coatings as well as the more recent hi - tech. systems. Like any other structure, a thin layered system may break down as the result of many causes. Among other types of failures, delamination defect is the most common mode of failure and particularly relevant to a thin layered system. This phenomenon which mostly occur between the upper layer directly subjectedto the load and the subsequent layer, is due to debonding or slippage at the interface of the two layers. A delamination may occur at the interface of a thin layered system even without any sign of failure in other parts of the structure. Steel wheeled trolleys and fork - lift trucks are among the most anticipated types of loading and causes of failures in the thin layered systems. Different combinations of thin layered systems were prepared using some special flooring materials, both in small and large scales. Despite the lack of any standard test, the action of a steel wheel rolling load on the ready made and purpose made specimens of thin layered systems was well simulated using the Steel Wheel Rolling Load Rig. The NUROLF, Newcastle University Rolling Load Facility, was also used for simulating the action of a tyred vehicle wheel rolling load on the thin layered systems of large scale. Some simple ways for detecting any possible delamination at the interface of the thin layered systems were examined. In addition to the available material characteristics tests, a relatively new simple shear box test was proposed for defming the relationship between normal stress and the correspondings hear strength for each combination of the materials at each age of the test. The results were then used as the basis for the subsequent structural analysis. The structural analysis of the systems was carried out for both of the experiments using the finite element method and the interface technique. In spite of the simplifications made in the solution, the analytical results were consistent with the experimental results to a considerable extent. Based on the results of this investigation, a relatively constitutive procedure was concluded for predicting the behaviour of a thin layered system under the action of a wheel rolling load with regard to the delamination defect.

In the rubber industry, plasticizers for rubber compounds mainly consist of petroleum derivatives. Consequently, the rubber industry is in constant competition with many petroleum consumers. This competition places an economic strain on rubber companies such as HEXPOL RUBBER COMPOUNDING L.L.C. In order to alleviate this strain, natural oil alternatives to petroleum plasticizers are of novel research interest and are investigated in this thesis project.

Plasticizers, as Bisphenol A (BPA) and Di-isononyl phthalate (DiNP), are chemicals added to the plastics to improve their performance, which recently, turned into a ubiquitous in the environment due to the high rate of use and manufacture of plastic, and hence, of the plasticizers. BPA and DiNP have been found in all environmental matrices, being bioavailable for organisms and reported as endocrine-disrupting chemicals (EDCs). On the other hand, the endocannabinoid system (ECS), a novel lipid signaling system lately defined, has been proposed as a new target for the potential effects of the EDCs. The ECS has been described in several species and it has an essential role for the well-being of the organisms. For that, the main goal of the present project was to assess the effects of BPA and DiNP in the ECS of Danio rerio and Sparus aurata. To accomplish this objective D. rerio and S. aurata were chronically treated (3 weeks) with BPA and DiNP, separately, via water or via food respectively. Generally, the results for both species, showed a deregulation of the ECS at central (brain) and peripheral level (liver and gonads) at mRNA and protein level, the alteration of the hepatic lipid metabolism and the biochemical composition of liver in both species. In the gonads, the reproductive performance measured as fertility rate, the gonadal morphology and sexual hormone levels were also altered by the treatments of both pollutants. In conclusion, the chronic exposure to environmental concentrations of BPA and DiNP induced alterations at the ECS pathway in Danio rerio and Sparus aurata. Finally, the ECS can be considered as new target for EDCs such as BPA and DiNP.

The pharmacokinetics, oral bioavailability, cerebrovascular permeability and biotransformation of the neurotoxic plasticiser n-butylbenzenesulfonamide (NBBS) were studied in order that the human health risk due to environmental exposure to NBBS could be evaluated. The pharmacokinetics of NBBS was determined in Wistar rats, following intravenous administration of the isotopomer [13C6] NBBS (1 mg/kg in 0.9% saline). [13C6] NBBS is cleared from plasma at a rate of 5 ml/min by the liver. The plasticiser has a short distribution phase (t1/2 of 47 seconds) and a long terminal phase (t1/2 of 17 hours). Plasma [13C6] NBBS concentrations, 24 hours after administration, represented 0.04% of the administered dose. These data indicated rapid uptake into tissue, which was subsequently confirmed by monitoring tissue concentrations of [13C6] NBBS for upto 8 hours following administration. [13C6] NBBS was not accumulated by any of the tissues studied (brain, liver, kidney, muscle and adipose tissue). Oral bioavailability was determined by simultaneously administering native NBBS orally and [13C6] NBBS intravenously to Wistar rats. The plasticiser was found to be absorbed erratically and subject to first pass metabolism. Plasma concentrations of orally administered NBBS fluctuated over the duration of the experiment. Furthermore, limitations posed by the assay resulted in truncated oral curves. These factors precluded estimation of areas under the oral NBBS curves to infinity and partial area ratios were instead used to calculate absolute bioavailability (mean of 19%). Cerebrovascular permeability of NBBS was determined with [13C6] NBBS, in Sprague-Dawley rats, using the in-situ brain perfusion technique of Takasato et al. (1984). The uptake of [13C6] NBBS into brain was very rapid and flow limited. Assuming an average cerebral perfusion fluid flow rate of 0.11 ml/s/g, the calculated single pass extraction value for [13C6] NBBS is 99.9% with a Kin of 0.11 ml/s/g. This is in close agreement with experimental values for the 15 second saline perfusions (extraction = 98% - 125% and Kin = 0.108 - 0.137). Differences in regional brain distribution of the plasticiser were not found. In-vitro biotransformation studies revealed one phase I metabolite in incubates of NBBS containing human, rabbit and rat post-mitochondrial supernatant (S9 fraction). This metabolite is 2-hydroxy-n-butylbenzenesulfonamide (NBBS-OH hydroxylated in the Based on these data, environmental exposure to NBBS does not pose a significant human health risk.

Poly(vinyl chloride) (PVC) processing requires the addition of plasticizers in large quantities to lower its glass transition temperature, thus increasing the flexibility and processability of the polymer. The extrusion of plasticizer into PVC does not lead to primary bonding and there is a tendency for leaching of the plasticizer into the surrounding environment. The most commonly used PVC plasticizer, di-2-ethylhexyl phthalate (DEHP), has become a ubiquitous environmental contaminant due to leaching, and there is incentive for the development of a "green" plasticizer replacement to minimize the environmental impact of PVC production and use.In this study, a method was developed to assess leaching of several poly(vinyl chloride) (PVC) plasticizers in aqueous media using gas chromatography (GC), and compared to a gravimetric standard test method (ASTM Method D1239). The gravimetric analysis test method proved to be inaccurate due to the uptake of aqueous media into the matrices of PVC samples. The GC method was a more direct measurement of plasticizer concentration in the aqueous phase. The leaching of commercial plasticizers, as well as several series of "green" candidate plasticizers, were assessed as a function of their molecular characteristics and compared to the industry standard PVC plasticizer, DEHP. It was found that plasticizers containing longer alkyl chains or non-polar branching emanating from polar structural units, increased the hydrophobicity of the molecule and reduced its aqueous leaching rate. Several "green" plasticizer candidates were found to minimize aqueous leaching to rates ten times below that of DEHP; notably dioctyl succinate (DOS), dihexyl maleate (DHM), methyl cyclohexyl diester (MCDE), diethylhexyl succinate (DEHS), hexanediol dibenzoate (C6), and the commercially available Hexamoll® DINCH. The methods and data presented in this thesis can be used as a tool in selecting a "green" plasticizer based on the leaching criterion, and aid in the selection of alternative plasticizers to the troublesome DEHP.
Le traitement de poly(chlorure de vinyle) (PVC) nécessite l'addition de larges quantités de plastifiants pour abaisser la température de transition vitreuse et pour augmenter la souplesse du polymère. L'extrusion de plastifiant dans le PVC ne conduit pas à des liaisons chimiques ce qui engendre une tendance à la lixiviation du plastifiant dans le milieu environnant. Le phthalate de bis(2-éthylhexyle) (DEHP), le plastifiant le plus utilisé avec le PVC, est devenu un polluant omniprésent dans l'environnement à cause de cette lixiviation. Ceci incite donc un intérêt accru envers le développement d'un plastifiant de remplacement, dit « vert », afin de minimiser l'impact environnemental de la production et de l'utilisation de PVC.Dans le cadre de cette thèse de recherche, une méthode d'évaluation de la lixiviation dans des milieux aqueux a été développée pour l'étude de plusieurs plastifiants utilisés avec le PVC. Cette méthode, basée sur la chromatographie en phase gazeuse (GC), a été comparée à une méthode gravimétrique standard (méthode ASTM D1239). La méthode gravimétrique s'est prouvée inutile à cause de l'absorption de l'eau dans les matrices PVC. La méthode GC a permis d'obtenir une mesure plus directe de la concentration de plastifiant dans la phase aqueuse. La lixiviation des plastifiants commerciaux, ainsi que de plusieurs séries de plastifiants « verts » proposés comme composés de remplacement a été évaluée. De plus, ces plastifiants ont été évalués en fonction de leurs caractéristiques moléculaires et comparés à la norme de l'industrie des plastifiants pour le PVC, le DEHP. Les résultats ont démontrés que des plastifiants constitués de chaînes alkyles plus longues ou de branchements non-polaires émanant des structures polaires, augmente l'hydrophobie de la molécule et réduit sa lixiviation dans la phase aqueuse. Pour plusieurs plastifiants « verts » candidats une lixiviation à des taux dix fois inférieur à celui de DEHP a été observée; notamment pour le succinate de dioctyle (DOS), le maléate de dihexyle (DHM), le méthyl cyclohexyle diester (MCDE), diéthylhexyle succinate (DEHS), le hexanediol dibenzoate (C6), et le plastifiant commercial Hexamoll® DINCH. Les méthodes et les données présentées dans cette thèse peuvent être utilisées comme un outil de sélection d'un plastifiant « vert » comme alternative à DEHP, fondée sur le critère de lixiviation.

Polyacrylonitrile (PAN) fiber is one of the most important synthetic fibers in the world because it is a precursor to carbon fiber. Compared to the traditional solution spinning process, the melting spinning process of PAN is less costly and can further reduce the price of PAN fiber. This dissertation is concerned with the objective of establishment of conditions (temperature, plasticizer type, and plasticizer composition) that a PAN copolymer is able to be stable melt spun with water based plasticizers. More specifically, PAN/water/acetonitrile (70/15/15) mixture is considered as reference sample in this study because it was proposed in a BASF patent in which it was claimed it could be stably melt spun. We are looking for a more benign plasticizer so that the use of acetonitrile can be avoided and PAN can still be stably melt spun. To achieve this objective, the first step is to measure the melting point (Tm) of PAN copolymer with various plasticizers and compositions by using differential scanning calorimetry (DSC). The results indicate the Tm of PAN copolymer can be reduced to around 160 oC with water only as a plasticizer, which is lower than the degradation temperature of PAN (180 oC). Moreover, using a water/ethanol mixture and water/acetonitrile as plasticizers can further reduce the melting point of PAN to 150 oC and 135 oC, respectively. The second step is conducting rheological measurements on the PAN/plasticizers mixture. A pressure chamber was designed and attached to the capillary rheometer in order to prevent the foaming and evaporation of plasticizers during the viscosity experiments. Both steady-shear and time-dependent viscosity measurements were conducted. The rheological measurement results indicate that PAN can keep stable for more than 120 minutes with all plasticizers under 170 oC, and it starts to degrade in 60 minutes at 180 oC, except samples plasticized with 30 wt% of water (which keep stable for 120 minutes as well). The steady-shear viscosity results indicate the shear-thinning behavior is observed for the PAN/plasticizer mixtures at a temperature ranging from 170 oC to 190 oC and provide the fundamental viscosity data which can be applied to the extrusion process. In conclusion, the rheological measurements show PAN/Water (70/30 wt%) at 180 oC and PAN/EtOH/Water (70/15/15) at 170 oC are two potential systems for carrying out the PAN melt spinning process. Scanning electron microscopy (SEM) images were taken for the reference state and potential conditions. These images show that the copolymer strands have more and larger voids when plasticized with water only compared to those plasticized with water/acetonitrile and water/ethanol mixture. In this case, PAN/EtOH/Water (70/15/15) at 170 oC is considered to be the most benign system for that PAN melt spinning.
Doctor of Philosophy
The melt spinning process of polyacrylonitrile (PAN) has been studied in the past few decades. Compared to the traditional solution spinning process, it does not require toxic organic solvents. The major problem of the PAN melt spinning process is the melting point (Tm) of PAN is much higher than its degradation temperature. However, by adding plasticizers the Tm of PAN can be significantly reduced, which makes PAN melt spinning feasible. In this work we discuss the feasibility of the melt spinning process of polyacrylonitrile (PAN) copolymer plasticized with water based plasticizers by using differential scanning calorimetry (DSC) and rheological methods. The objective is to use water only as a plasticizer to melt spin PAN under specific conditions (composition, temperature etc). The melting point and rheological measurements have been conducted by DSC and a modified capillary rheometer, respectively, for this plasticized system. The DSC results show that the melting point of the PAN copolymer can be reduced below the degradation temperature of PAN, and the rheological results show that the PAN copolymer can be extruded with a reasonable viscosity at 15-20 o v above its melting point, and also the stability and viscosity are strongly dependent on temperature and the plasticizer type and content. Furthermore, the Scanning electron microscopy (SEM) images show the copolymer strands extruded from PAN/H2O mixture have many more and larger voids than PAN/H2O/EtOH mixture. In conclusion, the results indicate that the most appropriate condition for PAN melt spinning is PAN/H2O/EtOH mixture of 70/15/15 wt% ratio at a temperature of 170 oC

Plasticizers are additives to plastics that impart flexibility and the ability to process polymers. Unfortunately, due to their leaching potential and widespread use, they have become ubiquitous contaminants in the environment. Studies have correlated the rise of many health issues to the chronic exposure to these compounds and have suggested them as potential carcinogens and endocrine-disruptors. In particular, available evidence indicates that they disturb steroid production such as testosterone production and therefore, behave as anti-androgens. The seriousness of this issue has prompted researchers to develop "green" plasticizers to avoid adverse effects. In this thesis, a series of potential alternative plasticizers were screened for their anti-androgenic potential in vitro using a mouse Leydig tumor cell line, the MA-10 cells. Optimal solvent and plasticizer concentrations and time frame conditions were determined to ensure viability of the cells for the duration of the experiments. Using these optimized testing conditions, potential green plasticizers, including the 1,3-propanediol (C3), 1,4-butanediol (C4), 1,5-pentanediol (C5) and 1,6-hexanediol (C6) dibenzoates, were studied by monitoring their effects on progesterone synthesis. Based on these results and those of others from our group, the candidature of C4 is supported as a potential green plasticizer.
Les plastifiants sont des adjuvants ajoutés aux formulations de plastiques pour les rendre plus flexibles et plus faciles à manipuler. Malheureusement, étant donné leur tendance à migrer de la matrice polymère et leur utilisation répandue, ils sont devenus des contaminants environnementaux omniprésents. Des études ont corrélé la hausse de certaines maladies à l'exposition chronique à ces composés et évoquent leurs risques en tant que potentiels carcinogènes et perturbateurs endocriniens. Notamment, il y a évidence qu'ils perturbent la formation de certains stéroïdes dont la testostérone et ainsi, agissent comme des anti-androgènes. L'importance de ce sujet a incité les chercheurs à développer des plastifiants ‘verts' pour éviter les effets négatifs associés à ces composés. Dans cette thèse, des composés alternatifs ont été testés pour leur effet anti-androgène in vitro avec la lignée cellulaire tumorale interstitielle du testicule de souris, les cellules MA-10. Des concentrations optimales de solvant et plastifiants ainsi qu'une durée optimale d'exposition ont été déterminées afin d'assurer la viabilité des cellules au cours des expériences. En employant les conditions optimales établies, des composés sélectionnés en tant que potentiels plastifiants verts, incluant les dibenzoates de 1,3-propanediol (C3), de 1,4-butanediol (C4), de 1,5-pentanediol (C5) et de 1,6-hexanediol (C6), ont été étudiés en mesurant l'impact sur la synthèse de progestérone. Les résultats de cette étude, appuyés par d'autres résultats de notre groupe, démontrent le potentiel du C4 en tant que potentiel plastifiant vert.

A solid phase extraction (SPE) method was developed for simultaneous extraction of dicarboxylic acids and diols formed during hydrolysis of poly(butylene succinate), PBS, and poly(butylene adipate), PBA. The developed SPE method and subsequent GC-MS analysis were used to extract, identify and quantify low molecular weight products migrating from linear and branched poly(butylene adipate) (PBA) and poly(butylene succinate) (PBS) during aging in aqueous media. The combination of SPE and GC-MS proved to be a sensitive tool, able to detect small differences in the degradation rate during early stages of hydrolysis before any significant differences were observed by weight loss and molecular weight measurements. The detected low molecular weight products included monomers i.e. adipic acid and 1,4-butanediol for the PBA polymers and succinic acid and 1,4-butanediol for PBS. Several dimers and trimers i.e. hydroxybutyl adipate, hydroxybutyl succinate, di(hydroxybutyl) adipate, di(hydroxybutyl) succinate and hydroxybutyl disuccinate were also detected. Best extraction efficiency for 1,4-butanediol and succinic acid was achieved with a hydroxylated polystyrene-divinylbenzene resin as solid phase. Linear range for the extracted analytes was 1-500 ng/ml for adipic acid and 2-500 ng/ml for 1,4-butanediol and succinic acid. Detection and quantification limits for all analytes were between 1-2 ng/ml (S/N=3) and 2-7 ng/ml (S/N=10) respectively. Relative standard deviations were between 3 % and 7 %. Comparison of measured weight loss and the amount of monomeric products showed that weight loss during early stages of hydrolysis was mainly caused by the release of water-soluble oligomers that on prolonged ageing were further hydrolyzed to monomeric species. Significant differences in degradation rate could be assigned to degree of branching, molecular weight, aging temperature and degradation medium.

Linear and branched PBA was mixed with PVC in solution cast films to study the effects of molecular weight and branching on plasticizer efficiency. Used as polymeric plasticizer, PBA formed a semi-miscible two-phase system with PVC where the amorphous part exhibited one single glass transition temperature and the degree of polyester crystallinity was dependent on molecular weight, degree of branching and blend composition. Plasticizing efficiency was favored by higher degree of branching and a 40 weight-percent polyester composition.

Modern indoor environments contain a vast array of contaminating sources. Emissions from these sources produce contaminant concentrations that are substantially higher indoors than outside. Because we spend most of our time indoors, exposure to indoor pollutants may be orders-of-magnitude greater than that experienced outdoors. Phthalate esters have been recognized as major indoor pollutants. They are mainly used as plasticizers to enhance the flexibility of polyvinylchloride (PVC) products, as well as in humectants, emollients, and antifoaming agents. Phthalates are found in a wide range of consumer products including floor and wall coverings, car interior trim, floor tiles, gloves, footwear, insulation on wiring, and artificial leather. Because these phthalate additives are not chemically bound to the polymer matrix, slow emission from the products to the surrounding air or other media usually occurs. Biomonitoring data suggest that over 75% of the U.S. population is exposed to phthalates. The ubiquitous exposure to phthalates is of concern because toxicological investigations have demonstrated considerable adverse health effects of phthalates and their metabolites. Studies have shown that exposure to phthalates results in profound and irreversible changes in the development of the reproductive tract, especially in males, raising the possibility that phthalate exposures could be the leading cause of reproductive disorders in humans. In addition, effects such as increases in prenatal mortality, reduced growth and birth weight, skeletal, visceral, and external malformations are possibly associated with phthalate exposure. Epidemiologic studies in children also show associations between phthalate exposure in the home and the risk of asthma and allergies. Given the ubiquitous nature of phthalates in the environment and the potential for adverse human health impacts, there is a critical need to understand indoor emissions of phthalates and to identify the most important sources and pathways of exposure. In this study, a model that integrates the fundamental mechanisms governing emissions of semi-volatile organic compounds (SVOCs) from polymeric materials and their subsequent interaction with indoor surfaces and airborne particles was developed. The emissions model is consistent with analogous mechanistic models that predict emission of volatile organic compounds (VOCs) from building materials. Reasonable agreement between model predictions and gas-phase di-2-ethylhexyl phthalate (DEHP) concentrations was achieved for data collected in a previously published experimental study that measured emissions of DEHP from vinyl flooring in two very different chambers. The analysis showed that while emissions of highly volatile VOCs are subject to “internal“ control (through the material-phase diffusion coefficient), emissions of the very low volatility SVOCs are subject to “external“– control (through partitioning into the gas phase, the convective mass transfer coefficient, and adsorption onto interior surfaces). Because of the difficulties associated with sampling and analysis of SVOCs, only a few chamber studies quantifying their emissions from building materials and consumer products are available. To more rigorously validate the SVOCs emission model and more completely understand the mechanisms governing the release of phthalate from polymeric building materials, the emission of DEHP from vinyl flooring was studied for up to 140 days in a specially-designed stainless steel chamber. In the duplicate chamber study, the gas-phase concentration in the chamber increased slowly and reached a steady state level of 0.9 µg/m3 after 30 days. By increasing the area of vinyl flooring and decreasing that of the stainless steel surface in the chamber, the time to reach steady state was significantly reduced, compared to the previous study (1 month vs. 5 months). The adsorption isotherm of DEHP on the interior stainless steel chamber surface was explicitly measured using two different methods (solvent extraction and thermal desorption). Strong adsorption of DEHP onto the stainless steel surface was observed and found to follow a simple linear relationship. In addition, parameters measured in the experiments were then applied in the fundamental SVOCs emission model. Good agreement was obtained between the predictions of the model and the gas-phase DEHP chamber concentrations, without resorting to fitting of model parameters. These chamber studies have shown that the tendency of SVOCs to adsorb strongly to interior surfaces has a very strong influence on the emission rate. Compared to the experimental chamber systems, however, the real indoor environment has many other types of surface that will adsorb phthalates to different extents. The emission rate measured in a test chamber may therefore be quite different to the emission rate from the same material in the indoor environment. For this reason, both a two-room model and a more representative three-compartment model were developed successively to estimate the emission rate of DEHP from vinyl flooring, the evolving gas-phase and adsorbed surface concentrations, and human exposures (via inhalation, dermal absorption and oral ingestion of dust) in a realistic indoor environment. Adsorption isotherms for phthalates and plasticizers on interior surfaces, such as carpet, wood, dust and human skin, were derived from previous field and laboratory studies. A subsequent sensitivity analysis revealed that the vinyl flooring source characteristics, as well as mass-transfer coefficients and ventilation rates, are important variables influencing the steady-state DEHP concentration and resulting exposures. A simple uncertainty analysis suggested that residential exposure to DEHP originating from vinyl flooring may fall somewhere between about 5 µg/kg/d and 180 µg/kg/d. The roughly 40-fold range in exposure reveals the inherent difficulty in using biomonitoring results to identify specific sources of exposure in the general population. This research represents the first attempt to explicitly elucidate the fundamental mechanisms governing the release of phthalates from polymeric building materials as well as their subsequent interaction with interior surfaces. The mechanistic models developed can most likely be extended to predict concentration and exposure arising from other sources of phthalates, other sources of other semi-volatile organic compounds (such as biocides and flame retardants), as well as emissions into other environmental media (food, water, saliva, and even blood). The results will be of value to architects, governments, manufacturers, and engineers who wish to specify low-emitting green materials for healthy buildings. It will permit health professionals to identify and control health risks associated with many of the SVOCs used in indoor materials and consumer products in a relatively inexpensive way.
Ph. D.