Dissertations / Theses on the topic 'Oxygen barrier propertie'

With increasing pollution and global warming of the environment, a wide spectrum of engineering technologies has emerged in food packaging to develop innovative materials with less carbon dioxide release and Green House emissions. Nowadays, an ideal food packaging must meet all the requirements of food safety and comply with environmental concerns concomitantly. One of the strategies to implement a food package that encompasses all consumer needs is to resort to eco-friendly laminates that combine several layers of materials with different functions in terms of gas/oil/water barrier and mechanical properties. The PhD research was focused on the replacement of currently used EVOH conventional gas barrier laminates with bio-based laminates containing cellulose nanocrystals (CNCs) for shelf-life extension of sensitive-oxidation foods products. Chemico-physically, cellulose is a microfibrillated structure, the most abundant biopolymer, made of millions of beta 1-4 glucose linked by glycosidic bonds; its hierarchical organization denotes from the crystalline and amorphous regions containing chains of glucose firmly hold together side-by-side by hydrogen bonds providing high tensile strength. CNCs are generally obtained by a chemical process called “top-down” either by acidic or oxidative hydrolysis of the amorphous part of cellulose. CNCs are biodegradable tiny particles whose at least one dimension is smaller than or equal to 100 nm. Actually, CNCs-coated polymers exhibit unique and extraordinary barrier properties to gases. However, since most biodegradable materials are hydrophilic by nature, CNCs tend to integrate water in wet environment which then allows the gases to pass through the coated polymers even abruptly. That phenomenon of water sensibility of CNCs was investigated in-depth during the first stage of the research and two solutions were considered plausible to alleviate that drawback, that of chemically modifying the CNCs surface for making them more hydrophobic or/and that of laminating the CNCs between two water-repellent plastic films to protect them from the humid surrounding. Standard (unmodified) and esterified (modified) CNCs were produced and characterizedto assess their functional groups, crystallinity index, apparent hydrodynamic diameter and size and hydrophilic behavior. Subsequently, plastic films were coated with standard and modified CNCs and characterized by the contact angle, Z-potential, gases permeability (Water vapor, O2, CO2). Coated-CNCs plastic films were then laminated with solvent-based polyurethanic adhesive and characterized by delamination test and gas permeability at 50% and 80% RH to evaluate the effectiveness of the lamination in the protection of CNCs coatings from the wet environment. Between 90% and 1200% improvement of gas barrier was achieved after the lamination.More importantly, the chemical modification of cellulose nanocrystals combined with the lamination resulted to be the best strategy to overcome the water sensitivity of CNCs in wet environment. Finally, a comparative food shelf-life assessment by using both synthetic (EVOH) and bio-based (CNCs) barriers laminates were successfully performed on grated cheese and ground coffee. The results obtained confirmed with certainty that CNCs implementation as a replacement of petroleum-based gas barrier is effective and that will contribute to develop more advanced and sustainable food packaging able to reduce the dependency on synthetic polymers and promoting a circular economy.

Biopolymers from renewable resources are of interest for packaging applications as an alternative to conventional petroleum-based polymers. One of the major application areas for biopolymers is food packaging, where a candidate polymer should meet critical requirements such as mechanical and oxygen barrier performance, also in humid conditions. Starch has long been used in certain packaging applications, either in plasticized state or blended with other polymers. However, native starch has high sensitivity to water and low mechanical and barrier performance. Recently, wood-derived hemicelluloses have been extensively studied as oxygen barrier films, but suffer from low film-forming ability and mechanical performance. In the present study, xyloglucan (XG) from tamarind seed waste is explored as an alternative high-performance biopolymer in packaging applications. The obstacles of polysaccharides in terms of moisture sensitivity and processability are addressed in this thesis. In Paper I, film properties of XG were studied. XG has a cellulose backbone, but unlike cellulose, it is mostly soluble in water forming highly robust films. Moisture sorption isotherms, tensile tests and dynamic mechanical thermal analysis were performed. Enzymatic modification (partial removal of galactose in side chains of XG) was performed to study the effect of galactose on solubility and filmforming characteristics. XG films showed lower moisture sorption than starch. Stiffness and tensile strength were very high of the order of 4 GPa and 70 MPa respectively, with considerable ductility and toughness. The thermomechanical performance was very high with a softening temperature near 260 ºC. In Paper II, several plasticizers were studied in order to facilitate thermal processing of XG films: sorbitol, urea, glycerol and polyethylene oxide. Films of different compositions were prepared and studied for thermomechanical and tensile properties. Highly favorable characteristics were found with XG/sorbitol system. A large drop in glass transition temperature (Tg) of XG of the order of 100 ºC with 20 - 30 wt% sorbitol was observed with an attractive combination of increased toughness. In Paper III, XG was chemically modified and the structure-property relationship of modified XG studied. XG modification was performed using an approach involving periodate oxidation followed by reduction. The oxidation is highly regioselective, where the side chains of XG are mostly affected with the cellulose backbone well-preserved as noticed from MALDI-TOF-MS and carbohydrate analysis. Films were cast from water and characterized by dynamic mechanical thermal analysis, dynamic water vapor sorption, oxygen transmission analysis and tensile tests. Property changes were interpreted from structural changes. The regioselective modification results in new types of cellulose derivatives without the need for harmful solvents. In Paper IV, moisture durability of XG was addressed by dispersing montmorillonite (MTM) platelets in water suspension. Oriented bionanocomposite coatings with strong in-plane orientation of clay platelets were prepared. A continuous water-based processing approach was adopted in view of easy scaling up. The resulting nanocomposites were characterized by FE-SEM, TEM, and XRD. XG adsorption on MTM was measured by quartz crystal microbalance analysis. Mechanical and gas barrier properties were measured, also at high relative humidity. The reinforcement in mechanical properties and effects on barrier properties were remarkable, also in humid conditions. In Paper V, cross-linked XG/MTM composite was prepared with high clay content (ca. 45 vol%) by an industrially scalable “paper-making” method. Instead of using cross-linking molecules, cross-linking sites were created on the XG chain by selective oxidation of side chains. The in-plane orientation of MTM platelets were studied using XRD and FE-SEM. The mechanical properties and barrier performance were evaluated for the resulting 'nacre-mimetic' nanocomposites. The elastic modulus of cross-linked nanocomposites is as high as 30 GPa, one of the stiffest bionanocomposites reported.

QC 20121107

Fluorescent light exposure has well documented negative effects on fluid milk through oxidation reactions. A shift to light-emitting diode (LED) lights in retail dairy cases has occurred due to increased energy efficiency, but the effects of LED light on fluid milk are not known. The objective was to study the interaction of light protective additives (LPA) with a high oxygen barrier package under fluorescent and LED lighting conditions simulating a retail refrigerated dairy case. The extent of oxidation in 2% milk packaged in polyethylene terephthalate (PET) packages with different light interference properties (UV barrier, 2.1% titanium dioxide (TiO2) LPA, 4.0% TiO2 LPA, 6.6% TiO2 LPA) under light exposure up to 72h was compared to control packages (light-exposed, light-protected). Chemical measures of oxidation included dissolved oxygen content, formation of secondary lipid oxidation products, riboflavin degradation, and volatile analysis by electronic nose. Changes in dissolved oxygen content were associated closely with oxidation changes in milk over 72h. PET with 6.6% TiO2 was the most successful package, based on triangle test methodology, protecting milk sensory quality similar to light-protected milk through 8h LED light exposure. Based on a 9-point hedonic scale, (1=dislike extremely, 9=like extremely), consumers liked milk stored under LED light more (α=0.05; 6.59 ± 1.60) than milk stored under fluorescent light (5.87 ± 1.93). LED light is less detrimental to milk quality than fluorescent light and PET with high levels of TiO2 can protect milk quality for short periods of time under typical retail storage conditions.
Master of Science in Life Sciences

L'objectif de la présente thèse est d'améliorer les propriétés barrières du MetPET en conditions sévères. Plus précisément d'établir les corrélations structure-propriétés : structure du primaire d'accroche déposé en ligne sur le film PET avant métallisation et propriétés barrières et d'adhésion métal en condition sèche et humide du composite final obtenu (MetPET). L'approche choisie est la polymérisation en émulsion en régime semi-continu. Cette approche permettra d'apporter un caractère hydrophobe (phase 1-Coeur) favorisant la barrière à l'humidité et un caractère hydrophile (phase 2-Ecorce) en surface présentant des groupes fonctionnels favorables à l'adhésion métal en condition humide. De plus nous avons aussi investigué l'influences de divers additifs de formulations afin d'optimiser les propriétés du primaire d'accroche. Les latex présentant une structure de type cœur/écorce est très favorable pour la barrière à l'humidité. En effet ces latex présentent une perméabilité à l'eau sensiblement plus faible que les latex sans structure (100% composition de l'écorce). Concernant la perméabilité à l'oxygène celle-ci est principalement assurée par la couche métallique. La formulation de nos latex cœur/écorce par des agents mouillants s'est révélé indispensable pour assurer un bon étalement de nos latex sur le substrat PET. En effet nos latex issus de la synthèse ont été synthétisés avec un minimum de tensio-actif, ce qui a eu pour effet négatif d'obtenir une tension de surface trop élevée pour assurer leur mouillabilité sur le film PET. De plus cet agent mouillant a aussi montré une influence positive sur les performances d'adhésion de la couche métal sur le film PET traité avec le primaire d'accroche. La formulation de nos latex cœur/écorce par un réticulant a montré un influence positive sur les propriétés barrières aux gaz et sur les performances d'adhésion métal. Cet agent réticulant tend à favoriser la réticulation entre particule et ainsi favoriser la formation d'un film continu barrière à l'eau. De plus celui-ci apporte des fonctions de type azoté favorable aux interactions avec les atomes métallique (aluminium)
The proposition of this work is to improve the barrier property of a laminate aimed to be applied in the field of packaging for foodstuffs. This laminate is constituted by a PET substrate metallized with aluminum deposited under vacuum. Given that PET is not a strongly polar polymer it is necessary to improve its adhesion to metals. This study was carried out in order to understand if there is a way to make sure that the polar groups will be bonded to the metal without being disturbed by the conditions of the environment. Our approach was the semi-batch emulsion polymerization, followed by the restructuration of the initial system (regular spherical polymeric nanoparticles) by changing its original morphology. Finally, the latexes were formulated by using variable amounts of compounds that were expected to improve the properties of the final material in terms of barrier and metallic adhesion. A part of the latexes synthesized in the scope of this work was submitted to pilot trials in an industrial line of PET extrusion. The latexes were used to coat the PET inline. The core-shell nanoparticles presented a lower permeability to water than the particles synthesized in the absence of the seed. This was related to the tortuosity promoted by the core, which increases the pathway of a diffusing molecule. The permeability to oxygen was found to be mainly related to the metallic layer. Given that the latexes were synthesized with the minimum amount of tensioactive necessary to originate stable dispersions, the wettability agent was found to be indispensable for the proper spreading of the coatings onto the PET. Furthermore, this compound played an important role on the adhesion property of the films. The cure agent, in the correct concentration, promotes the adhesion to metallic substrates. Moreover, this compound helped to prevent the interaction of the wettability agent with the water, decreasing consequently the plasticization of the structure in conditions of high humidity

The development of flexible lightweight OLED devices requires oxygen/moisture barrier layer thin films with water vapour transmission rates (WVTR) of < 10-6 g/m2/day. This thesis reports on single and multilayer architecture barrier layers (mostly based on SiO2, Al2O3 and TiO2) deposited onto glass, Si and polymeric substrates using remote plasma sputtering. The reactive sputtering depositions were performed on Plasma Quest S500 based sputter systems and the morphology, nanostructure and composition of the coatings have been examined using SEM, EDX, STEM, XPS, XRD and AFM. The WVTR has been determined using industry standard techniques (e.g. MOCON) but, for rapid screening of the deposited layers, an in-house permeation test was also developed. SEM, XRD and STEM results showed that the coatings exhibited a dense, amorphous structure with no evidence of columnar growth. However, all of the single and multilayer coatings exhibited relatively poor WVTRs of > 1 x 10-1 g/m2/day at 38 °C and 85 % RH. Further characterisation indicated that the barrier films were failing due to the presence of substrate asperities and airborne particulates. Different mechanisms were investigated in an attempt to reduce the density of film defects including incorporation of a getter layer, modification of growth kinetics, plasma treatment and polymer planarising, but none were successful in lowering the WVTR. Review of this issue indicated that the achievement of good barrier layers was likely to be problematic in commercial practice due to the cost implications of adequately reducing particulate density and the need to cover deliberately non-planar surfaces and fabricated 3D structures. Conformal coverage would therefore be required to bury surface structures and to mitigate particulate issues. Studies of the remote plasma system showed that it both inherently delivered an ionised physical vapour deposition (IPVD) process and was compatible with bias re-sputtering of substrates. Accordingly, a process using RF substrate bias to conformally coat surfaces was developed to encapsulate surface particulates and seal associated permeation paths. An order of magnitude improvement in WVTR (6.7 x 10-2 g/m2/day) was measured for initial Al2O3 coatings deposited with substrate bias. The development of substrate bias to enhance conformal coverage provides significant new commercial benefit. Furthermore, conformal coverage of 5:1 aspect ratio structures have been demonstrated by alternating the substrate bias between -222 V and -267 V, with a 50 % dwell time at each voltage. Further development and optimisation of the substrate bias technique is required to fully explore the potential for further improving barrier properties and conformal coverage of high aspect ratio and other 3D structures.

As a very promising material of copper diffusion barrier for next generation microelectronics, Ru has already obtained a considerable attention recently. In this dissertation, we investigated ruthenium and ruthenium oxide electrochemical properties and the application as a copper diffusion barrier. Cu under potential deposition (UPD) on the RuOx formed electrochemically was first observed. Strong binding interaction, manifesting by the observed Cu UPD process, exists between Cu and Ru as well as its conductive ruthenium oxide. Since UPD can be conformally formed on the electrode surface, which enable Ru and RuOx has a potential application in the next generation anode. The [Cl-] and pH dependent experiment were conducted, both of them will affect UPD Cu on Ru oxide. We also found the Cu deposition is thermodynamically favored on RuOx formed electrochemically. We have studied the Ru thin film (5nm) as a copper diffusion barrier. It can successfully block Cu diffusion annealed at 300 oC for 10min under vacuum, and fail at 450 oC. We think the silicidation process at the interface between Ru and Si. PVD Cu/Ru/Si and ECP Cu/Ru/Si were compared each other during copper diffusion study. It was observed that ECP Cu is easy to diffuse through Ru barrier. The function of RuOx in diffusion study on Cu/Ru/Si stack was discussed. In pH 5 Cu2+ solution, Ru and Pt electrochemical behavior were investigated. A sharp difference was observed compared to low pH value. The mechanism in pH 5 Cu2+ solution was interpreted. An interesting compound (posnjakite) was obtained during the electrochemical process. An appropriate formation mechanism was proposed. Also Cu2O was formed in the process. We found oxygen reduction reaction is a key factor to cause this phenomenon.

Poly(lactic acid) is biodegradable polymer derived from renewable resources and non-toxic, which has become most interested polymer to substitute petroleum-based polymer. However, it has low glass transition temperature and poor gas barrier properties to restrict the application on hot contents packaging and long-term food packaging. The objectives of this research are: (a) to reduce coagulation of graphene oxide/single-walled carbon nanotube (GOCNT) nanocomposite in poly(lactic acid) matrix and (b) to improve mechanical strength and oxygen barrier property, which extend the application of poly(lactic acid). Graphene oxide has been found to have relatively even dispersion in poly(lactic acid) matrix while its own coagulation has become significant draw back for properties of nanocomposite such as gas barrier, mechanical properties and thermo stability as well as crystallinity. Here, single-walled carbon nanotube was hybrid with graphene oxide to reduce irreversible coagulation by preventing van der Waals of graphene oxide. Mass ratio of graphene oxide and carbon nanotube was determined as 3:1 at presenting greatest performance of preventing coagulation. Four different weight percentage of GOCNT nanocomposite, which are 0.05, 0.2, 0.3 and 0.4 weight percent, were composited with poly(lactic acid) by solution blending method. FESEM morphology determined minor coagulation of GOCNT nanocomopsite for different weight percentage composites. Insignificant crystallinity change was observed in DSC and XRD data. At 0.4 weight percent, it prevented most of UV-B light but was least transparent. GOCNT nanocomposite weight percent was linearly related to ultimate tensile strength of nanocomposite film. The greatest ultimate tensile strength was found at 0.4 weight percent which is 175% stronger than neat poly(lactic acid) film. Oxygen barrier property was improved as GOCNT weight percent increased. 66.57% of oxygen transmission rate was reduced at 0.4 weight percent compared to neat poly(lactic acid). The enhanced oxygen barrier property was ascribed to the outstanding impermeability of hybrid structure GOCNT as well as the strong interfacial adhesion of GOCNT and poly(lactic acid) rather than change of crystallinity. Such a small amount of GOCNT nanocomposite improved mechanical strength and oxygen barrier property while there were no significant change of crystallinity and thermal behavior found.
Master of Science

There is actual investigation of the processes creating the buried barrier layers that prevent diffusion of high-temperature coating materials because of the development of ion and ion-plasma technologies, surface treatment of material. In the present work we discuss the results on the thermal stability, structure, physical and mechanical properties of the buried barrier layers formed 2*1018 ion/sm2 , by ion implantation of oxygen and carbon (the dose the energy of 1.5 – 2 MeV) accelerator to the DC-60. Nuclear spectroscopic techniques involving X-ray analysis systematic studies of the influence of the buried barrier layer on the thermally induced processes in the layered system Fe-Be. It is established: the sequence of phase transitions in the surface layers and inside the sample during isothermal annealing. It is shown that the implanted oxygen ions buried barrier layer in the matrix of Fe slow mutual diffusion of beryllium atoms and iron atoms. The kinetics of the process of mutual diffusion of Fe and Be in a solution Fe (Be) for both multi-layered systems with a layer of implanted of oxygen and without it. The evolution of the distribution of the oxygen implanted layer in the copper and the effect of thermal annealing. It is shown that even at an annealing temperature of ~ 200ºC in this system is the diffusion of oxygen into the sample of copper. Consequently, the oxygen cannot be used as a subsurface barrier layer in copper, in contrast to iron, where oxygen-implanted layer remains stable at much higher temperatures. The research phase formation in iron implanted with carbon and deposited on the surface layer of beryllium. It is established that the sample implanted with a layer of carbon formation on the surface Fe2 phase begins after 5 hours annealing at 650ºC. For the case without implantation – education phase not fixed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20897

Environmental concerns arising from the use of non-degradable plastics have resulted in search for suitable substitutes. The thesis deals with new nanostructured composites based on reinforcement of nanocellulose whiskers in "green" polymers such as xylan. Since the reinforcement filler and the matrix are both biobased and are thereby environmental friendly. Xylan incorporated with cellulose whiskers films provided with improved water and oxygen barrier properties. It appears that the high degree of crystallinity of cellulose whiskers, dense composite structure formed by the whiskers and rigidly hydrogen-bonded cellulose whiskers can cause cellulose whiskers to form integrated matrix which contribute to substantial benefit in the overall reduction of transmission rate. The spectral data obtained for the NCW/xylan nanocomposite films showed that the amount of xylan adsorbed to cellulose increases with the addition of NCW in the matrix. In addition, NMR T2 relaxation experiments studies were conducted to investigate the change in the nature of carbohydrate-water interactions as a result of NCW incorporation. These results facilitated an improved understanding of the mechanisms involved in the superior barrier and mechanical properties of xylan-whisker nanocomposite films. XRD studies show that when a xylan-whisker nanocomposite films is formed the mixing occurs on the atomic scale and NCW loading increases the matrix crystallinity.

L’EVOH est un copolymère thermoplastique semi-cristallin composé de segments de polyéthylène et d’alcool polyvinylique de proportion variable. Grâce notamment à une importante densité d’énergie cohésive lui conférant d’excellentes propriétés barrière à l’oxygène et aux arômes en condition anhydre, ce matériau est aujourd’hui largement utilisé dans l’élaboration d’emballages alimentaires multicouches. Sa grande sensibilité à l’eau, provoquant une détérioration importante des propriétés du matériau en conditions hydratées, reste cependant la principale problématique liée à son utilisation actuelle. Dans ce contexte, les travaux ont dans un premier temps porté sur la compréhension approfondie du comportement d’hydratation de l’EVOH afin de mettre en évidence des relations propriétés-structure, ce qui n’avait pas été réalisé jusqu’à présent. Deux axes de recherches ont ensuite été développés dans le but d’améliorer les propriétés barrière du matériau aussi bien à l’état anhydre qu’à l’état hydraté, tout en conservant une bonne transparence et une tenue mécanique correcte: le mélange de polymère d’une part, et l’approche nanocomposite d’autre part. Le choix de la voie fondu, procédé de mise en œuvre peu décrit dans la littérature pour ces systèmes, et celui des charges ont été guidés par la possibilité de transposer facilement les études à l’échelle industrielle
EVOH is a semi-crystalline thermoplastic copolymer composed of polyethylene and polyvinyl alcohol segments in various contents. Thanks to an important cohesive energy density leading to excellent oxygen and food aromas barrier properties in anhydrous state, this material is currently widely used in the elaboration of multilayer food packaging. Its high moisture sensitivity, causing an important deterioration of the properties of the material in hydrated conditions, still constitutes the main inconvenient for its current use. In this context, the studies were firstly focused on the detailed comprehension of the hydration behavior of EVOH in order to underline properties-structure relations, which was still unrealized. Two research axes were then developed in order to improve the barrier properties of the material in both dry and hydrated states, while remaining mechanical behavior and transparency stable: the polymers blend, on the one hand, and the nanocomposite approach on the other hand. The choice of the melting way, rarely described in the literature for these systems, and the one of the fillers nature were dictated by the possibility to easily transpose the experiments to an industrial scale

La cellulosa è il polimero naturale più abbondante sulla terra, una risorsa rinnovabile che ogni anno viene prodotta in miliardi di tonnellate da molti organismi vegetali. Per questa ragione, su di essa si sta concentrando una crescente attenzione nell’ipotesi di una sua sempre maggiore applicazione nei più diversi campi. Quello del food packaging, che è ancora fortemente dipendente da materiali di sintesi e provenienti da risorse non rinnovabili, è particolarmente interessato ad un suo più ampio impiego, anche con il fine di aumentare la sostenibilità dei suoi prodotti e di ridurne l’impatto ambientale. Con questa tesi di dottorato si è inteso mettere a fuoco le potenzialità di impiego della nano cellulosa (cellulose nanocrystals, CNs), sperimentare la produzione e valutare le proprietà di alcune lacche a base di CNs, destinate a ricoprire convenzionali materiali flessibili per il confezionamento alimentare. La tesi si compone di quattro parti distinte. Nella prima parte si è inteso rappresentare lo stato dell’arte delle conoscenze e delle applicazioni della nanocellulosa, attraverso un ampio lavoro di documentazione bibliografica. Dapprima si è voluto mettere a fuoco quanto noto sulla struttura e la classificazione delle varie forme di nanocellulosa che è oggi possibile produrre e, a proposito della cellulosa nanocristallina in particolare, si è fatto il punto sulle tecniche di preparazione, la morfologia e le principali applicazioni. Da questo lavoro di documentazione sono emerse le notevoli proprietà di barriera ai gas ed a potenziali migranti, le eccellenti proprietà meccaniche (resistenza alla rottura, massima elongazione tensile, modulo di Young) e le interessanti caratteristiche termiche (transizione vetrosa, punto di fusione e di decomposizione) della CNs da sola ed in combinazione con altri materiali. Nella seconda sezione della tesi, al fine di comprendere meglio la struttura e la morfologia dei nanocristalli di cellulosa ottenuti attraverso un processo di idrolisi acida di linter di cotone, sono state utilizzate diverse tecniche analitiche avanzate, sia per la caratterizzazione qualitativa che quantitativa. E’ stato così possibile ottenere informazioni precise sulle dimensioni dei nano cristalli, il rapporto di forma, la solubilità e numerose altre loro importanti proprietà. In particolare le tecniche di TEM, SEM, e AFM sono apparse come le più adatte per osservare la morfologia dei cristalli, studiare le caratteristiche e la rugosità delle superfici trattate con lacche a base di CNs. Si è inoltre indagato sulla distribuzione delle dimensioni dei cristalli ottenuti e, grazie all’uso di FTIR, XPS e NMR, sulla natura dei gruppi funzionali disponibili e sulle loro interazioni. La terza parte della tesi è dedicata ad uno studio delle proprietà di alcuni differenti film, largamente impiegati per il food packaging (PET, OPP, OPA e cellophane), rivestiti con uno strato sottile di CNs. In particolare, è statomesso a punto il processo di laccatura e sono state misurate le proprietà ottiche (la trasparenza, l’opacità e le proprietà anti-fog), il coefficiente di frizione statico e dinamico, le energie superficiali e gli angoli di contatto, le proprietà di barriera all’ossigeno ed al vapor d’acqua. Da questo lavoro è emerso come sia effettivamente possibile rivestire di uno strato sottile (intorno ad un micron di spessore), omogeneo e continuo, film plastici differenti e che attraverso questo processo di laccatura, si riduce significativamente il coefficiente di frizione, si incrementano le proprietà anti-fog, si aumenta decisamente la barriera all’ossigeno, senza pregiudicare la trasparenza dei film di supporto. La prospettiva molto concreta è quella di costituire, in un modestissimo spessore, un coating multifunzionale con spiccate caratteristiche di sostenibilità e di sicurezza alimentare. L’ultima sezione della tesi è dedicata al lavoro fatto per sperimentare la possibile applicazione di una tecnica di rivestimento molto moderna (layer-by-layer coating, LbL) che sfrutta la formazione di legami elettrostatici tra biopolimeri caricati diversamente. In particolare si è dimostrata la possibilità di costituire lacche di un composito ottenuto mediante la sovrapposizione alternata di sottilissimi strati (da 6 a circa 30 nm) di chitosano e cellulosa nanocristallina. Il diverso pH delle soluzioni in cui vengono dispersi i due biopolimeri determina un diverso grado di ionizzazione delle cariche, rispettivamente positive del chitosano e negative della cellulosa, e di conseguenza diversi spessori e proporzioni relative dei due biopolimeri nel coating composito che si realizza. Ciò, evidentemente, permette di modulare in un ampio intervallo di valori, la permeabilità del film ricoperto. Il coefficiente di permeabilità del composito giunge a valori pari 0.02 cm3 µm m-2 24h-1 kPa-1, molto simili a quelli espressi da copolimeri a base di EVOH, in condizioni anidre. I vantaggi di un simile rivestimento sono comunque fondamentalmente legati alla sicurezza e non tossicità dei biopolimeri impiegati, dalla loro sostenibilità e dall’ampio grado di libertà disponibile nel modulare le caratteristiche finali di barriera, secondo le esigenze del prodotto da confezionare. Lo strato di lacca LbL così costituita rappresenta, in definitiva, una barriera all’ossigeno particolarmente promettente negli impieghi reali più critici anche per la concreta possibilità di realizzarla convenientemente su oggetti tridimensionali come bottiglie, vassoi e altri imballaggi finiti. In conclusione, le ricerche condotte rappresentano una base di partenza molto promettente per un’innovazione di sostenibilità e di prestazioni nel campo dell’imballaggio flessibile e meritano ulteriori approfondimenti ed applicazioni.
Being cellulose the most abundant natural polymer in biosphere, more and more attention has been paid on its new functionalities, sustainability, and renewability. Meanwhile, food packaging materials is one of the largest products we are using in daily life, but most of conventional materials are still oil-based due to their low cost and good performances. Therefore, in order to improve the sustainability and renewability of food packaging materials, this PhD dissertation focuses on development new nano-material (cellulose nanocrystals, CNs) for food packaging and includes mainly four sections. In the first section of this PhD dissertation, we reviewed the progress in knowledge on nano-cellulose first and then, specifically, on CNs. In this section the structure and classifications of various nano-cellulose preparations are included, as well as the preparation, the morphologies, and applications of CNs. In CNs applications, we reviewed that it exhibits excellent barrier, mechanical, and thermal properties itself or combined with other polymers. Particularly, the barrier properties refer to oxygen, water vapor, and migration barrier; mechanical properties are related with tensile strength, Young’s modulus, and strain percentage; the thermal properties include glass transition and melting or decomposition temperature, heat flow, and thermal mechanical parameters. In the second section of this PhD dissertation, to better understand the structure and status of CNs itself or in other polymers, we have used different powerful analytical tools for qualification and quantification. Firstly, we have obtained the relatively precise dimensions of CNs and observe its redispersability in different solvents, mainly water solutions. In the following, we could gain the information of the CNs status in other polymers in order to interpret the final performance efficiently. Finally, we preliminarily concluded that TEM, SEM, and AFM are suitable tools for observing individual crystals, estimating the roughness, and learning the morphology in different scale, respectively. As for the size distribution, functional groups, and interactions between the atoms of CNs, the particle size distributor, FTIR, XPS, and NMR are used for determinations, respectively. In the third section of this PhD dissertation, we have systematically investigated the properties of conventional films coated with CNs. In particular, we have analyzed their optical properties (transparency and haze), mechanical properties (static and dynamic coefficient of friction), anti-fog (contact angle and surface energy) and barrier properties (oxygen and water vapor transmission rates). In doing this, we have demonstrated that CNs coatings mainly lead to a reduction of friction, a premium feature for industrial applications, and that their influence on the optical properties of the packaging is not significant. Excellent anti-fog property guarantees customers more conveniently to evaluate the product inside the packages easily. At last but not the least, CNs coatings dramatically improve not only the oxygen barrier properties of conventional flexible food packaging, but also lead to a certain reduction in the water vapor transmission rate. The perspective use of CNs as multi-functional coatings favors a reduction of the required thickness for plastic films, towards a more environmentally-friendly and sustainable approach to packaging. In the last section of this PhD dissertation, we demonstrated the use of chitosan (CS)/CNs nanocomposites realized by layer-by-layer (LbL) self-assembly as oxygen barrier under different pH combinations. The oxygen permeability coefficient of CS/CNs nanocomposites is as low as 0.02 cm3 µm m-2 24h-1 kPa-1, close to EVOH co-polymers, under dry conditions. Meanwhile, we consider that CNs has no potential risks for human beings and the renewable origin of the carbohydrate polymers as significant added values that justify a deeper investigation. Finally, it deserves to be underlined also the chance of finely tuning the oxygen permeability by means of the pH values and the sharp control of the thickness associated with this process. Therefore, based on the advantages outlined above, the LbL CS/CNs nanocomposite represents a promising oxygen barrier component in transparent flexible packaging materials and semi rigid tridimensional objects (bottles, trays, boxes and etc.). Based on our researches, we conclude that CNs leads to very promising applications in food packaging field and deserves to be further investigated in the future.

This work describes three alternative processes for producing microfibrillated cellulose (MFC) in which pulp fibres are first pre-treated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated with a combined enzymatic and mechanical pre-treatment. In the two other processes, cell wall delamination was facilitated by pre-treatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethyl cellulose (CMC) onto the fibres. All three processes are industrially feasible and enable production with low energy consumption. Using these methods, MFC can be produced with an energy consumption of 500–2300 kWh/tonne, which corresponds to a 91–98% reduction in energy consumption from that presented in earlier studies. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long.

QC 20120928

This work describes three alternative processes for producing microfibrillated cellulose (MFC; also referred to as cellulose nanofibrils, CNF) in which bleached pulp fibres are first pretreated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated by a combined enzymatic and mechanical pretreatment. In the two other processes, cell wall delamination was facilitated by pretreatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethylcellulose (CMC) to the fibres. All three processes are industrially feasible and enable energy-efficient production of MFC. Using these processes, MFC can be produced with an energy consumption of 500–2300 kWh/tonne. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long. The MFCs were also evaluated in a number of applications in paper. The carboxymethylated MFC was used to prepare strong free-standing barrier films and to coat wood-containing papers to improve the surface strength and reduce the linting propensity of the papers. MFC, produced with an enzymatic pretreatment, was also produced at pilot scale and was studied in a pilot-scale paper making trial as a strength agent added at the wet-end for highly filled papers.

QC 20150126

Des films nanocomposites amidon / argent ont été préparés par deux voies de génération vertes de nanoparticules d'argent. La première voie, dite ex situ, consiste à préparer tout d'abord une solution colloïdale d'argent qui est ensuite redispersée dans une matrice amidon plastifiée glycérol. Les nanoparticules d'argent colloïdales sont synthétisées en solution aqueuse par réduction du nitrate d'argent par du glucose en présence d'amidon stabilisant. La seconde voie, dite in situ, consiste à disperser le nitrate d'argent dans le film amidon plastifié et le réduire directement dans le film par traitement thermique en présence ou non de réducteur. L'influence du taux de glucose réducteur, du temps de synthèse et de la température a été étudiée en termes de taille, distribution de taille et dispersion des nanoparticules d'argent dans les films nanocomposites ex situ et in situ. Tout en gardant des paramètres de procédé comparables, les deux voies de nanostructuration des films amidon/argent ont également été comparées en termes de structure, de propriétés thermiques et de transport. Enfin, l'incorporation de charges montmorillonites a également été étudiée dans les deux voies de génération des nanoparticules métalliques. L'ensemble des travaux a permis de valider les deux voies de génération vertes menant à des nanoparticules d'argent dispersées de manière homogène et de tailles moyennes inférieures à 30 nm. La voie in situ à 85°C se distingue par des nanoparticules d'argent cristallines et de très petites tailles (inférieures à 10 nm) avec une interface amidon/argent cohésive particulière qui permettent d'améliorer les propriétés barrières aux gaz et à l'eau avec une diminution de perméabilité observée jusqu'à 90%
The present work reports a strategy involving the preparation of silver nanoparticles in a biodegradable polymer stemming from either an ex situ or an in situ method, using in both cases a completely green chemistry process. The influence of the reducing agent concentration and the silver nanoparticles generation route is investigated on the structure, the morphology and the properties of the nanocomposite films. In both routes, silver nanoparticles with a diameter below 30 nm were highlighted in the nanocomposite films. For all nanocomposite films, no modification on the crystalline structure of the starch matrix is observed in the presence of silver. The in situ generation route allowed to obtain the smallest silver nanoparticles with a diameter below 10 nm. Crystalline silver nanoparticles were obtained only from the in situ generation route at the temperature of 85°C. The introduction of montmorillonites in both generation routes was also studied. The decrease of the water sorption and the improvement of water and oxygen barrier properties were found to be not dependent on the reducing agent concentration but mainly on the presence of the crystalline structure of the silver nanoparticles. Thus, significant enhancement of the barrier properties were finally obtained for the in situ nanocomposite films thanks to an efficient interaction between the crystalline silver nanoparticles and the starch matrix

Le manuscrit porte sur l'élaboration de couches minces ayant des propriétés barrières aux liquides, aux gaz et aux ultra-violets. Pour réaliser nos différents systèmes, la technologie plasma à décharge à barrière diélectrique à la pression atmosphérique (DBD) a été utilisée. Dans la première partie, des films polymère plasma à base de 1H, 1H, 2H, 2H, Perfluorodecyl acrylate ont été développé. En fonction des paramètres plasma une surface dîtes superhydrophobe en une étape a été obtenue grâce à l'obtention d'un film composé de nanoparticules fluorés. La seconde partie des travaux a consisté à développer des films barrières aux gaz à partir de l'hexamethyldisiloxane. Ainsi, des films minces SiOx et multicouches SiOxHyCz/SiOx ont pu être obtenue afin d'améliorer les performances barrières de substrat PET et PEN. Enfin, l'obtention de film barrière aux UV a consisté à une croissance in-situ de nanoparticules de dioxyde de titane (TiO2) à partir du film polymère plasma. La matrice polymère constitué d'une structure siloxane et aminée plasma joue le rôle de nano-réacteur pour la croissance de cristaux de TiO2.

碩士
聖約翰科技大學
自動化及機電整合研究所
100
This article is mainly concentrating on Parylene chemical vapor deposition , surface improvement and treatment of substrate as well as analysis of film on Glass、PMMA、Aluminum and its surface adhesion by dipping under A-174 silane solution and conducting on plasma treatment(18 W). Those results can be further analyzed by parylene, which has the characteristic of organic thin film and mechanical properties. Experiments focusing on adhesion of surface treatment of substrate have shown that 600 nm thick glass of deposition on parylene C thin film is able to carry out the maximum capacity raised from 14.1 mN to 18.5 mN. As a result, thin film adhesion can be greatly improved by surface treatment. Secondly, to package flexible organic light-emitting diode components, using PET substrate to manufacture package-chip to experimentally estimate its water vapor transmission rate. To compare the results of surface treatment by using A-174 silane solution and Plasma treatment (18 W) with original one, the water vapor transmission rate result has shown that PET dipping within A-174 silane solution with 600 nm depositing package-chip has better insulation result, which obtaining 3.02 g/m2 × day. To the application of package components, package-chip and Parylene thin film have essentially effect on insulation, but the result has not come out as we anticipate ideally. The possible reason to explain it would be there is an limitation on the characteristic of monomer performance for organic material. To enhance its quality and characteristic, organic material should be combined with other material such as most prevalent used of ABS material, which has characteristic of collision-resistant, good thermal stability and easy processing characteristics. as well as combination of multiple polymer.

A relatively new type of reinforced composite material, derived from immiscible blends of thermoplastic homopolymers, is characterised in this doctoral research. Microfibril Reinforced Composites (MFCs) utilise common engineering and commodity polymers to create high strength and stiffness microfibrils dispersed in an isotropic matrix. Unlike traditional polymer composites, MFCs use the dispersed component of a blend to create an even distribution of in situ reinforcing microfibrils via a simple extrusion, drawing and processing technique. This research quantifies the mechanical and oxygen gas barrier properties of polyolefin-based MFCs containing polyethylene terephthalate (PET) microfibrils. It is concerned not only with identifying MFCs with the best properties, but also with how manufacturing parameters influence those properties. Characterisation is split into several parts. Initial investigations into blend development during extrusion and drawing were conducted. The main purpose of this was to gain a better understanding of the factors influencing the morphological changes that occur during production. Blend viscosity ratio and capillary number were identified as key factors in determining the onset of coalescence, deformation and break up of the dispersed polymer. The effects on microfibril formation of several important manufacturing parameters were highlighted, with die diameter and extrusion speed the most influential of these. A significant skin-core microstructure was observed. Formation of elongated microfibres (with negligible molecular chain alignment) was shown to occur during extrusion, which was subsequently justified via modelling of the shear stress flow fields in the die. Drawn blends gave very high tensile strengths and stiffnesses due to highly oriented molecular chains. A threshold draw ratio of 3.5, at which properties change considerably, was identified. Mechanical properties of injection moulded MFCs from polypropylene were not considerably better than the neat matrix polymer. However, those from polyethylene (PE) showed significant improvement via injection moulding and directional compression moulding. MFCs with just 30% microfibril content displayed tensile properties up to six times greater than neat PE. Measurements of oxygen gas permeability highlighted improvements of up to 65%. Processing and cooling conditions were shown to significantly influence permeability via a Taguchi experimental design analysis. MFC storage containers from PE/PET were injection moulded as proof-of-concept on completion of the research.

Numerous studies have focused on enhancing the flame retardant behavior of cotton and polyurethane foam. Some of the most commonly used treatments (e.g., brominated compounds) have raised concerns with regard to toxicity and environmental persistence. These concerns have led to significant research into the use of alternative approaches, including polymer nanocomposites prepared from more environmentally benign nanoparticles. These particles migrate to the surface from the bulk during fire exposure to form a barrier on the surface that protects the underlying polymer. This theory of fire suppression in bulk nanocomposites inspired the use of layer-by-layer (LbL) assembly to create nanocoatings in an effort to produce more effective and environmentally-benign flame retardant treatments. Negatively charged silica nanoparticles of two different sizes were paired with either positively charged silica or cationic polyethylenimine (PEI) to create thin film assemblies. When applying these films to cotton fabric, all coated fabrics retained their weave structure after being exposed to a vertical flame test, while uncoated cotton was completely destroyed. Micro combustion calorimetry confirmed that coated fabrics exhibited a reduced peak heat release rate, by as much as 20% relative to the uncoated control. Even so, this treatment would not pass the standard UL94 vertical flame test, necessitating a more effective treatment. Positively- charged chitosan (CH) was paired with montmorillonite (MMT) clay to create a renewable flame retardant nanocoating for polyurethane foam. This coating system completely stops the melting of a flexible polyurethane foam when exposed to direct flame from a butane torch, with just 10 bilayers (~ 30 nm thick). The same coated foam exhibited a reduced peak heat release rate, by as much as 52%, relative to the uncoated control. This same nanobrick wall coating is able to impart gas barrier to permeate plastic film. Multilayered thin films were assembled with "green" food contact approved materials (i.e., chitosan, polyacrylic acid (PAA) and montmorillonite clay). Only ten CH-PAA-CH-MMT quadlayers (~90 nm thick) cause polylactic acid (PLA) film to behave like PET in terms of oxygen barrier. A thirty bilayer CH-MMT assembly (~100 nm thick) on PLA exhibits an oxygen transmission rate (OTR) below the detection limit of commercial instrumentation (<= 0.005 cm^3/(m^2*day*atm)). This is the same recipe used to impart flame retardant behavior to foam, but it did not provide effective FR to cotton fabric, so a very different recipe was used. Thin films of fully renewable electrolytes, chitosan and phytic acid (PA), were deposited on cotton fabric in an effort to reduce flammability through an intumescent effect. Altering the pH of aqueous deposition solutions modifies the composition of the final nanocoating. Fabrics coated with highest PA content multilayers completely extinguished the flame and reduced peak heat release (pkHRR) and total heat release of 60% and 76%, respectively. This superior performance is believed to be due to high phosphorus content that enhances the intumescent behavior of these nanocoatings.

碩士
國立臺灣科技大學
高分子工程系
94
An investigation of the oxygen barrier properties of the modified polyamide and nylon clay (MPAyNYC) compound and blow the films is reported first, and blends with different percentage of EVOH in optimization conditions MPA12NYC1 to produce MPAyNYCEVOH barrier resins and blow the films, preparation and discussed the optimization of composition and mechanism of the (MPAy12NYC1)x EVOHy series films. Relative to PE membrane sample, at 25℃ / 65% relative humidity, the oxygen permeation rate was slowly obvious, and that is improved 31.4 and 34.9 times than PE specimen. EVOH specimen is the best result of whole matrix plastic of oxygen barrier properties, the oxygen barrier properties is improved 16133.3 times than PE specimen. An astonishing phenomenon, at 25℃ / every relative humidity, the oxygen permeation rate of MPAyNYC series films is lower than those MPAy and NYC membrane. Moreover, this improvement in oxygen permeation rate reach the best as the MPA contents present in MPAyNYC approach the 12:1 optimum weight ratio of MPA to NYC. On the other hand, the oxygen permeation rate of (MPAy12NYC1)xEVOHy specimen slower than those MPAy12NYC1 specimen, at every relative humidity. The oxygen permeation rate reach lowest as the weight ratio of MPAy12NYC1 to EVOH reached about 4:1. For instance, at 65% relative humidity, the oxygen permeation rate of (MPAy12NYC1)4EVOH1 is about 7.7 (25μm • cm3 / m2 • day • atm), which yield about 628 times oxygen barrier improvements better than that of the PE specimen. Relatively to EVOH specimen, although the oxygen permeation rate increase gradually as relative humidity increase that of the MPAyNYC and (MPAy12NYC1)x EVOHy series specimen, but the range of increased is to be smaller than EVOH specimen. To realize these interesting oxygen permeation barrier mechanisms, the morphology, FT-IR, rheological behavior, wide-angle X-ray diffraction patterns, thermal properties and characteristic of free volume have been every discussed in this paper.