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1
Guo, Molin. "PROCESSING-STRUCTURE-PROPERTY RELATIONSHIPS INCO-CONTINUOUS POLYMER BLENDS AND COMPOSITES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1593786851492932.
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Holloway, Matthew James. "Electrically conducting composites formed from polymer blends." Thesis, Brunel University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316533.
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Johnson, Jack Royce III. "POLYMER BLENDS, COMPOSITES AND AEROGEL MODIFICATION BY INNOVATIVE APPROACHES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1317409667.
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Villechevrolle, Viviane Louise. "Polymer blends for multi-extruded wood-thermoplastic composites." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/v_villechevrolle_121008.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Mar. 2, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.
5
Cankaya, Burhan Fuat. "Foamed Eva-bitumen Blends And Composites." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610215/index.pdf.
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The thermal conductivities of foamed polymer based materials are much lower thermal conductivity values than unfoamed polymeric materials. Especially, thermal conductivity values of foamed polymers with closed-cell structure decreases to 0.03
W/m.K. The reinforcement of foamed polymeric materials by mixing with bitumen lowers the raw material cost.
The main objective of this study is to make a new thermal insulation material with low thermal conductance. In this study, the effects of concentration of calcium carbonate as inorganic filler and the effects of cross-linking on the properties foamed and unfoamed ethylene-vinyl acetate (EVA) copolymer based bituminous blends and composites were investigated. Applications such as thermal, mechanical characteristics of foamed and unfoamed EVA based bituminous composites were investigated.
Foamed EVA based bituminous composites were prepared by using Brabender Plastic Coder, PLV 151. Mixing was made at 120 ºC at 60 rpm for 15 minutes. The prepared blends were molded by a technique called Hand Lay-up Self-expanding Batch Molding (HLUSEBM) which was firstly applied by our group. The molding temperature was 170 º
C at which chemical blowing agent and cross-linking agent decomposes. According to test results, at moderate chemical blowing agent and EVA content, the best closed-cell structure with high porosity and low thermal conductivity values were obtained. The compressive properties of foamed polymer based bituminous composites (FPBBCs) increase with increasing CBA and EVA content. With increasing calcium carbonate and EVA concentration, the porosity of FPBBCs increases but thermal conductivity of them decreases. On the other hand, with increasing filler content but with decreasing EVA concentration elastic modulus of FPBBCs increases but elastic recovery decreases.
6
Iyer, Subramanian. "Structure Property Relationships in Polymer Blends and Composites. Part I - Polymer/POSS Composites Part II - Poly(ethylene terepthalate) ionomer/Polyamide 6 Blends Part III - Elastomer/Boron Nitride Composites." online version, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1152121344.
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O'Donnell, Hugh J. "In situ composites of compatibilized polypropylene/liquid crystalline polymer blends." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-02052007-081243/.
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Cheerarot, Onanong. "The effects of nanoparticles on structure development in immiscible polymer blends." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/the-effects-of-nanoparticles-on-structure-development-in-immiscible-polymer-blends(cca9d075-dfcd-46c5-b865-290c414b4315).html.
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Composites based on binary polymer blends of polystyrene (PS)/poly(ethylene-co-vinyl alcohol) (EVOH) (70/30 wt%) containing natural Montmorillonite, Na-MMTs (Nanomer PGW or Cloisite Na+) and organically modified Montmorillonite clays, OMMTs (Nanomer I.30T, Cloisite 30B or Cloisite 10A) were prepared via melt compounding. The interactions between the polymers and clays were studied using flow micro-calorimetry (FMC). Data obtained from FMC indicated that the probe molecule mimicking EVOH (butan-2-ol) interacted with the MMTs and OMMTs much more strongly than PS. Scanning electron microscopy (SEM) revealed that composites based on binary blends had dispersed/continuous morphologies, in which EVOH was dispersed in a PS matrix. The size of the EVOH droplets in the PS matrix increased with increasing clay loading. Transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) were used to determine the extent of dispersion and location of clay in the PS/EVOH/clay composites. These techniques confirmed the formation of intercalated clay structures. As predicted by FMC, the clay platelets were selectively located in the EVOH phase, independent of the blending sequence and the type of organic modifier in the OMMT. Composites containing OMMTs showed better dispersion of platelets within the EVOH phase than those containing Na-MMTs. Differential scanning calorimetry (DSC); showed the crystallisation behaviour of EVOH to depend on the clay loading and the nature of the organic modifier in the OMMT. Nanomer PGW, Cloisite Na+ and Cloisite 30B acted as weak nucleating agents. In contrast, Nanomer I.30T and Cloisite 10A significantly hindered the crystallisation of EVOH in the blends due to the restriction of chain segment mobility. Dynamic mechanical thermal analysis (DMTA) confirmed that the presence of clay increases the storage modulus of the composites compared to an unfilled blend. In addition, the improvement in storage modulus reflected the dispersion state of the different clays and their interaction with the polymers of the blend. Ternary-blend based composites were formed by adding poly(styrene-co-acrylonitrile) (SAN) to the composites based on binary PS/EVOH blends. This resulted in a finer dispersion of the EVOH phase and the development of a core-shell morphology, in which SAN encapsulated and formed shells around EVOH droplets. In contrast to binary blend composites, the clay platelets were found at the interface between SAN and EVOH in the ternary blends.
9
Sharma, Suraj. "Fabrication and characterization of polymer blends and composites derived from biopolymers." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1239894269/.
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Lim, Kate. "Supramolecular polymer blends for composite matrices." Thesis, University of Reading, 2016. http://centaur.reading.ac.uk/66400/.
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This research project reports a new approach to thermoplastic composite matrix design, in which a low-MW polymer additive acts as a plasticiser and flow-promoter at high temperatures, but as a non-covalent cross-linking agent at lower temperatures. Thus, poly(aryl ether ketone)s (PAEKs) are functionalised with π-electron rich terminal groups and blended with π-electron deficient polyimides. A non-covalent charge-transfer stacking interaction between the two polymers forms a self-assembled supramolecular network. Carbon fibre composites with matrices composed of these supramolecular polymer blends were produced, and the thermomechanical performance of these materials are reported. In designing functionalised PAEKs, novel benzoyl-pyrene and -perylene derived compounds were synthesised. The synthesis of these compounds and their subsequent use as functional end-groups in polycondensations are also discussed. During the course of polymer synthesis, the effect of varying polymerisation conditions involving different alkali metal carbonates was systematically investigated. It was found that monomer sequence distribution in PAEKs can be controlled by changing the alkali metal cation used in the nucleophilic synthesis. The mechanism of modifying monomer sequence distribution is presented herein. Investigating the interaction of polycyclic aromatic molecules pyrene and perylene with binary co-polyimides containing both strongly-binding and weakly-binding diimide sequences results in the emergence of fractal-like patterns in the 1H NMR spectra of the polyimide. The polyimide spectrum at high intercalator loadings shows self-similarity over a range of different length scales.
11
Henry, Milliman W. "REINFORCEMENT OF MELT-BLEND COMPOSITES; POLYMER-FILLER INTERACTIONS, PHASE BEHAVIOR, AND STRUCTURE-PROPERTY RELATIONSHIPS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1323439686.
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Aronow, Roger Lockwood. "Toughening mechanisms in composites of miscible polymer blends with rigid filler particles." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35520.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006.Vita.
Includes bibliographical references (leaves 97-98).
Fillers are often added to polymers improve stiffness at the cost of reduced toughness, but this tradeoff is not universal. Well-dispersed microscopic particles have been shown to improve toughness and stiffness simultaneously in some cases. The effect depends on interparticle distance as well as interfacial adhesion. This type of toughening has been more successful in semicrystalline than in amorphous systems. An amorphous polymer blend was chosen to elucidate the effect of matrix properties on the toughening mechanism. The ternary blend of PMMA, PVC, and DOP (a common plasticizer) was characterized using TEM, and was found to be miscible over much of the PVC-rich domain. The blend Tg's fit well to an empirical model, which was used to predict a constant-Tg ([approx.] 40°C) blend series. Mechanical testing showed a wide, systematic variation in properties among these blends, although all were brittle in tension. The blend 90% PVC / 10% DOP was mixed with barium sulfate filler and evaluated for toughness in slow tension. In general, the composites showed decreasing toughness with increasing filler content. However, several specimens at 5 vol% filler exhibited a large increase in ductility and toughness ([approx.] 19-fold).
(cont.) SEM examination of tough specimens revealed several important findings: (1) Filler is present both as micron-scale agglomerates and as well dispersed particles. (2) Well-dispersed particles remain bonded to the matrix even for large deformations. (3) Filler agglomerates are prone to debonding and internal fracture, creating void space and enabling deformation. Base blend properties significantly affect the response to filler. The blend 8% PMMA / 80% PVC / 12% DOP showed small increases in ductility for 5 and 10 vol% filler, with the best result being a 10 vol% specimen showing a 6-fold toughness increase over the neat-blend average. This specimen showed similar microscopic behavior to the 90/10 blend, i.e. agglomerate debonding and fracture, but to a lesser degree. The blend 16% PMMA / 70% PVC / 14% DOP, showed no significant toughening. Also investigated were high-Tg ([approx.] 70°C) blends, which were brittle and became weaker with filler, and low-Tg ([approx.] 30°C) blends, which were intrinsically ductile and were not toughened by filler.
by Roger Lockwood Aronow.
Ph.D.
13
Bandi, Suneel A. "HIGH PERFORMANCE BLENDS AND COMPOSITES: PART (I) CLAY AEROGEL/POLYMER COMPOSITES PART (II) MECHANISTIC INVESTIGATION OF COLOR GENERATION IN PET/MXD6 BARRIER BLENDS." online version, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1152638697.
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McNally, John Anthony. "Studies on blends of polymers with bitumen." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318801.
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venoor, varun. "Investigation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Natural Rubber blends and Polystyrene/Polybutadiene Silica Nano-Composites." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492725718211967.
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Yang, Yan. "Characterization of polyethylene terephthalate, cellulose acetate and their blends." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-03302010-020651/.
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Milliman, Henry. "REINFORCEMENT OF MELT-BLEND COMPOSITES; POLYMER-FILLER INTERACTIONS, PHASE BEHAVIOR, AND STRUCTURE-PROPERTY RELATIONSHIPS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1326738846.
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Kalloudis, Michail. "Thin polymer films of block copolymers and blend/nanoparticle composites." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7894.
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In this thesis, atomic force microscopy (AFM), transmission electron microscopy (TEM) and optical microscopy techniques were used to investigate systematically the self-assembled nanostructure behaviour of two different types of spin-cast polymer thin films: poly(isoprene-b-ethylene oxide), PI-b-PEO diblock copolymers and [poly(9,9-dioctylfluorene-co-benzothiadiazole)]:poly[9,9- dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB conjugated polymer blends. In the particular case of the polymer blend thin films, the morphology of their composites with cadmium selenide (CdSe) quantum dot (QD) nanoparticles was also investigated. For the diblock copolymer thin films, the behaviour of the nanostructures formed and the wetting behaviour on mica, varying the volume fraction of the PEO block (fPEO) and the average film thickness was explored. For the polymer blend films, the effect of the F8BT/TFB blend ratio (per weight), spin-coating parameters and solution concentration on the phase-separated nanodomains was investigated. The influence of the quantum dots on the phase separation when these were embedded in the F8BT:TFB thin films was also examined. It was found that in the case of PI-b-PEO copolymer thin films, robust nanostructures, which remained unchanged after heating/annealing and/or ageing, were obtained immediately after spin coating on hydrophilic mica substrates from aqueous solutions. The competition and coupling of the PEO crystallisation and the phase separation between the PEO and PI blocks determined the ultimate morphology of the thin films. Due to the great biocompatible properties of the PEO block (protein resistance), robust PEO-based nanostructures find important applications in the development of micro/nano patterns for biological and biomedical applications. It was also found that sub-micrometre length-scale phase-separated domains were formed in F8BT:TFB spin cast thin films. The nanophase-separated domains of F8BT-rich and TFB-rich areas were close to one order of magnitude smaller (in the lateral direction) than those reported in the literature. When the quantum dot nanoparticles were added to the blend thin films, it was found that the QDs prefer to lie in the F8BT areas alone. Furthermore, adding quantum dots to the system, purer F8BT and TFB nano-phase separated domains were obtained. Conjugated polymer blend thin films are excellent candidates for alternatives to the inorganic semiconductor materials for use in applications such as light emitting diodes and photovoltaic cells, mainly due to the ease of processing, low-cost fabrication and mechanical flexibility. The rather limited optoelectronic efficiency of the organic thin films can be significantly improved by adding inorganic semiconducting nanoparticles.
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Leadbitter, J. "Structure-property relationships in reaction injection moulded polymers and polymer composites : Structure-property studies of reaction injection moulded polyurethanes, polyesters, polyacrylates and novel acrylic-urethane blends and of composites of these." Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384311.
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Li, Yilong. "Vapor sensing behavior of sensor materials based on conductive polymer nanocomposites." Technische Universität Dresden, 2019. https://tud.qucosa.de/id/qucosa%3A38069.
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This work aims to investigate the vapor sensing behavior of conductive polymer composites (CPCs). In connection with the protection of the environment and human beings, sensing of different kinds of chemical vapors is of increasing importance. At the moment, four kinds of vapor sensors are widely investigated and reported, namely semiconducting metal oxide sensors (MO), conjugated polymer sensors, carbonaceous nanomaterial based sensors, and CPC based sensors. Due to their unique component systems, the different sensor types are based on different sensing mechanisms resulting in different potential application ranges.
In consideration of cost and processability, CPC based vapor sensors are promising owning to their low cost, excellent processability, and designable compositions. In terms of vapor sensing behavior of CPC sensors, the interaction between the polymer and the organic vapor is a decisive factor in determining the sensing performance of CPCs. Ideally, the chosen polymer matrix should be able to swell without dissolving during vapor exposure so that the conductive network within the matrix can be disconnected, giving rise to the resistance change of CPCs. In some reported cases, polymers such as PLA and polycaprolactone (PCL) are degradable polymers, which are not durable when being exposed to environmental conditions for a long time. Therefore, it is necessary to make sure whether the selected polymers are resistive to vapors or not. There are two options for the polymer selection. One is to select a polymer that is only swellable in a specific or few organic solvents; another one is to select a polymer that is swellable to a variety of solvents. Since CPC sensors are used for detecting as many as possible hazardous chemicals to human beings or environment, the second case is more desired because of its broader window of detection. The solubility parameter is effective to characterize the interaction of polymers and organic solvents/vapors, which was firstly proposed by Charles Hansen. Initially, the Hansen solubility parameter (HSP) was used to predict the compatibility between polymer partners, chemical resistance, permeation rates, and even to characterize the surface of fillers. Liquids with similar solubility parameter (δ) are miscible, and polymers will dissolve in solvents whose δ is similar to their own value. This behavior is recognized as “like dissolves like”. Based on the description above, CPCs that can be used as liquid/vapor sensor materials should meet the following two requirements: 1) the chosen polymer should be swellable to vapors; 2) the CPCs as sensor materials have to be electrically conductive. Therefore, the relationship between conductive network and vapor sensing behavior of CPCs was investigated from the following aspects:
1) According to the previous studies, CB/polymer composites exhibit poor reversibility in cyclic vapor sensing tests because of the susceptible conductive network formed by CB particles. Thus, there is a need to improve the reversibility and increase the relative resistance change (Rrel) of CPCs. MWCNTs, as 1-dimensional carbon fillers with high aspect ratio, have excellent electrical and mechanical properties. Therefore, a hybrid filler system (MWCNT and CB) was utilized and incorporated in polycarbonate (PC) via melt compounding. PC was selected as the polymer matrix of CPCs because it showed high affinity with many commercial organic solvents/vapors as well as high and fast volume change upon organic solvents/vapors. In order to discuss the effect of conductive network formation on the vapor sensing behavior of PC/MWCNT/CB composites, two MWCNT contents were selected, which were lower and higher than the electrical percolation threshold of the PC/MWCNT composites. In the following, three CB contents were selected for the mixtures with MWCNT. The conductive networks composed of either MWCNT or hybrid CB/MWCNT are compared. The morphology of CPCs with different hybrid filler ratios was observed and investigated using SEM and OM. Moreover, to quantify the vapor sensing behavior of CPCs, some organic solvents were chosen and characterized by Flory-Huggins interaction parameter to demonstrate the polymer-vapor interaction. Afterwards, the cyclic vapor sensing was applied to illustrate the vapor sensing behavior of CPCs with different conductive network formations.
2) At moment, the filler dispersion is still a big challenge for MWCNT filled polymer composites due to the fact that the strong Van der Waals force among nanotubes makes them easily to entangle with each other resulting in the formation of agglomerates. A good filler dispersion state is desirable to achieve CPCs with low φc and. In order to reduce the φc of CPCs, immiscible polymer blend systems are introduced, which can have different blend microstructures by adjusting the polymer component ratios. In the second section, an immiscible polymer blend system based on two amorphous component, namely PC and polystyrene (PS), was chosen aiming to explain the influence of the blend morphology on the sensing performance of CPCs. PC/PS blends with different compositions filled with MWCNT were fabricated by melt mixing. The selective localization of MWCNTs in the blends was predicted using the Young’s equation. Moreover, the composite morphology, filler dispersion, and distribution were characterized by SEM and TEM. In the following, three kinds of CPCs ranging from sea-island structure to co-continuous structure were selected for the cyclic sensing measurement. The relationship between composite microstructure and resulting vapor sensing behavior was evaluated and discussed.
3) The poor reversibility of CPCs towards good solvent vapors is still a problem that hinders the cyclic use of CPC sensor materials. As an important class of polymer, crystalline polymers are rigid and less affected by solvent penetration because of the well-arranged polymer chains. Therefore, the effect of polymer crystallinity on the vapor sensing behavior of CPCs is imperative to be studied. In the third section, poly(lactic acid) (PLA), a semi-crystalline polymer, was selected to melt-mixed with PS and MWCNTs with the aim to improve the sensing reversibility of CPCs towards organic vapors, especially good solvent vapors. Thermal annealing was utilized to tune the PLA crystallinity and the polymer blend microstructure of CPCs. The electrical, morphological, and thermal behavior of CPCs after different thermal annealing times is discussed. In the following, the effect of crystallinity on the vapor sensing behavior of the CPCs was studied in detail. Besides, the different sensing performances of the CPCs towards different vapors resulted from the selective localization of MWCNTs and increased polymer matrix crystallinity were investigated and compared.
4) As discussed for the amorphous polymer blends and crystalline polymer blends and their vapor sensing behavior. The comparison of compact and porous structure of CPCs is going to be studied. In the fourth section, studies to further improve the sensing performance and to find out the exact sensing mechanism of CPCs were performed. Therefore, poly(vinylidene fluoride) (PVDF), a solvent resistive polymer, was chosen to be melt-mixed with PC and MWCNTs. In order to compare the MWCNT dispersion and localization in the blends, three kinds of PCs with different molecular weights were selected; hence, the viscosity ratio of immiscible blends was varied. Rheological, morphological, and electrical properties of CPCs were characterized. After that, the cyclic sensing and long-term immersion tests of CPCs towards different vapors were carried out to evaluate the vapor sensing behavior of compact CPCs with different blend viscosity ratios. Moreover, porous CPC sensors were prepared by extracting the PC component. The same sensing protocols were also applied to these porous sensor materials. The sensing mechanisms between compact CPC sensor and porous CPC sensor were compared and investigated.
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Joseph, Ronald Matthew. "Synthesis and Characterization of High Performance Polymers for Gas Separation and Water Purification Membranes and as Interfacial Agents for Thermplastic Carbon Fiber Composites." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/96219.
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This dissertation focuses on the synthesis and characterization of high performance polymers, specifically polybenzimidazoles (PBIs) for gas separation applications and polyimides (PI) for water purification and as interfacial agents for thermoplastic carbon fiber composites.
Two methods for improving the gas transport properties (for H2/CO2 separation) of a tetraaminodiphenylsulfone (TADPS)-based polybenzimidazole were investigated. Low molecular weight poly(propylene carbonate) (PPC) and poly(ethylene oxide) (PEO) were incorporated as sacrificial additives that could be removed via a controlled heat treatment protocol. PBI films containing 7 and 11 wt% PPC (blend) and 13 wt% PEO (graft) were fabricated and the gas transport properties and mechanical properties after heat treatment were measured and compared to the PBI homopolymer. After heat treatment, the 7 wt% PPC blend exhibited the highest performance while retaining the toughness exhibited by the PBI homopolymer.
Novel sulfonated polyimides and their monomers were synthesized for use as interfacial agents and water purification membranes. Polyimides are high performance polymers that have high thermal, mechanical, and chemical stability. The objective was to assess structure-property relationships of novel sulfonated polyimides prepared by direct polymerization of the diamine monomers. A series of sulfonated polyimides was synthesized using an ester-acid polymerization method with varying degrees of sulfonation (20%, 30%, and 50% disulfonated and 50% and 100% monosulfonated polyimides). The results showed that the toughness of the polyimides in the fully hydrated state was much better than current commercial cation exchange membranes.
A 100% disulfonated polyimide (sPI) and poly(amic acid) salt (PAAS) using the same monomers used for the synthesis of Ultem® were utilized as suspending agents for the fabrication of coated sub-micron polyetherimide (PEI) particles. Sub-micron particles were obtained using 1 wt% PAAS and 4 wt% sPI to coat the PEI. The PEI particles were coupled onto ozone treated carbon fibers using a silane coupling agent. SEM images showed a significant amount of particle coating on the treated carbon fibers compared to the non-silane treated carbon fibers.PHD
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Yilmaz, Gokhun. "Effects Of Titanate Coupling Agents On Low Density Polyethylene And Polypropylene Blends And Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610135/index.pdf.
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The objective of this study is to investigate the effects of titanate coupling agents on low density polyethylene (LDPE) and polypropylene (PP) blends and composites in terms of their mechanical and morphological properties. PP and LDPE composites were produced separately in a Brabender internal mixer, and CaCO3 was used as inorganic filler with compositions of 20, 40 and 60 %. PP/LDPE blends were produced in a twin-screw extruder with ratios of 75/25, 50/50 and 25/75. Their composites were prepared with addition of untreated and titanate-treated CaCO3 at 20% filler content.
Titanate coupling agent which is appropriate for LDPE, PP and CaCO3 was used to improve the mechanical properties of the blends and composites. For this purpose, &ldquoLica 12&rdquo
which is a kind of neoalkoxy organotitanate was used. Two forms of Lica 12 were used: powder form (Capow L12) and pellet form (Caps L12). Samples with and without titanate were prepared and then they were injection molded to make specimens for tensile and impact tests. Tensile fracture surfaces of samples were examined by scanning electron microscopy (SEM). Their mechanical and morphological properties were compared with each other to determine the effects of Lica 12. This study showed that Capow L12 improved strain at break and impact strength of PP/CaCO3 composites and PP/LDPE blends containing 75% and 50% PP. The strain at break value of of PP75 composite with 20% titanate-treated filler increased significantly up to 509% which is the highest value among all blends and composites in this study. Capow L12 exhibited its functions in PP matrix much more effectively than in LDPE matrix.
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Wang, Yuhua. "Conductive Thermoplastic Composite Blends for Flow Field Plates for Use in Polymer Electrolyte Membrane Fuel Cells (PEMFC)." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2893.
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This project is aimed at developing and demonstrating highly conductive, lightweight, and low-cost thermoplastic blends to be used as flow field bipolar plates for polymer electrolyte membrane (PEM) fuel cells. The research is focused on designing, prototyping, and testing carbon-filled thermoplastic composites with high electrical conductivity, as well as suitable mechanical and process properties.
The impact of different types of fillers on the composite blend properties was evaluated, as well as the synergetic effect of mixtures of fill types within a thermoplastic polymer matrix. A number of blends were produced by varying the filler percentages. Composites with loadings up to 65% by weight of graphite, conductive carbon black, and carbon fibers were investigated. Research results show that three-filler composites exhibit better performance than single or two-filler composites.
Injection and compression molding of the conductive carbon filled polypropylene blend was used to fabricate the bipolar plates. A Thermal Gravimetric Analysis (TGA) was used to determine the actual filler loading of composites. A Scanning Electron Microscope (SEM) technique was use as an effective way to view the microstructure of composite for properties such as edge effects, porosity, and fiber alignment. Density and mechanical properties of conductive thermoplastic composites were also investigated. During this study, it was found that 1:1:1 SG-4012/VCB/CF composites showed better performance than other blends. The highest conductivity, 1900 S/m in in-plane and 156 S/m in through plane conductivity, is obtained with the 65% composite. Mechanical properties such as tensile modulus, tensile strength, flexural modulus and flexural strength for 65% 1:1:1 SG-4012/VCB/CF composite were found to be 584. 3 MPa, 9. 50 MPa, 6. 82 GPa and 47. 7 MPa, respectively, and these mechanical properties were found to meet minimum mechanical property requirements for bipolar plates. The highest density for bipolar plate developed in this project is 1. 33 g/cm³ and is far less than that of graphite bipolar plate.
A novel technique for metal insert bipolar plate construction was also developed for this project. With a copper sheet insert, the in-plane conductivity of bipolar plate was found to be significantly improved. The performance of composite and copper sheet insert bipolar plates was investigated in a single cell fuel cell. All the composites bipolar plates showed lower performance than the graphite bipolar plate on current-voltage (I-V) polarization curve testing. Although the copper sheet insert bipolar plates were very conductive in in-plane conductivity, there was little improvement in single cell performance compared with the composite bipolar plates.
This work also investigated the factors affecting bipolar plate resistance measurement, which is important for fuel cell bipolar plate design and material selection. Bipolar plate surface area (S) and surface area over thickness (S/T) ratio was showed to have significant effects on the significance of interfacial contact resistances. At high S/T ratio, the contact resistance was found to be most significant for thermoplastic blends. Other factors such as thickness, material properties, surface geometry and clamping pressure were also found to affect the bipolar plate resistance measurements significantly.
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Salaeh, Subhan. "Élaboration des composites et mélanges à base de caoutchouc naturel : relations structure - propriétés." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10141/document.
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Le caoutchouc naturel (NR) et le caoutchouc époxydé (ENR) ont constitué la base de cette étude consacrée à l’étude des composites et mélanges de polymères. La présence du groupe époxyde a conduit à une amélioration des propriétés mécaniques de ces formulations en termes de module et de la résistance à la traction. De plus, l’utilisation de la spectroscopie diélectrique a révélé que les ENRs présentent une conductivité plus élevée que le NR à basse fréquence et à haute température. En particulier, le caoutchouc naturel époxidé contenant 50 mol% de groupes époxyde ENR-50 présente des conductivités et permittivités les plus élevées. Par conséquent, ce dernier a été choisi pour préparer des composites polymères en incorporant des particules de titanate de barium (BT) et de noir de carbone (CB). Les résultats montrent que la permittivité et conductivité des composites élaborés augmentent avec le taux d'incorporation de ces charges. Par exemple, les composites BT/ENR-50 atteignent une permittivité élevée 48.7 pour 50 vol% de BT. De plus, les composites CB/ENR-50 présentent un seuil de percolation de 6.3 vol% de CB. Enfin les mélanges à base de poly(fluorure de vinylidène) (PVDF) et d’ENR ont été étudiés. Il a été observé que la morphologie de ces mélanges dépend du degré d’époxydation du caoutchouc naturel et bien entendu de la composition du mélange. Une morphologie co-continue peut être observée dans l’intervalle 40 et 60% en masse d’ENR-50. En outre, les résultats issus d’analyses dynamiques mécanique et diélectrique montrent que ces mélanges présentent une miscibilité partielle. Enfin, des composites à base de ces mélanges binaires PVDF/ENR- 50 contenant BT ont été préparés. L’étude des morphologies a révélé que les particules de BT étaient dispersées dans la phase d’ENR-50 pour le mélange classique. Cependant, les particules de BT sont localisées à l'interface et dans la phase PVDF pour le mélange réticulé dynamiquement. En termes de propriétés, la permittivité plus élevée est obtenue pour le mélange PVDF/ENR 50 (80/20) ayant été réticulé dynamiquementNatural rubber (NR) and epoxidized natural rubber (ENR) were chosen to study the composites and blends of polymers. The presence of epoxide group caused to improve the mechanical properties in terms of modulus and tensile strength. Furthermore, dielectric spectroscopy revealed that ENR showed conductivity process at low frequency and high temperature. Epoxidized natural rubber containing 50 mol% of epoxide group or ENR-50 exhibited the highest dielectric permittivity and electrical conductivity. Therefore, ENR-50 was then selected to prepare polymer composite filled with barium titanate (BT) and carbon black (CB) particles. The permittivity and conductivity of the composites increased with the volume content of the fillers. The BT/ENR-50 composites reached a high permittivity of 4 8 . 7 for addition of 50 vol% BT. Meanwhile, CB/ENR-50 composite reached percolation threshold at 6. 3 vol% of CB. The phase development and miscibility of poly(vinylidene fluoride) (PVDF)/epoxidixed natural rubber (ENR) blends were then investigated. It was also found that phase structure depended on epoxidation level and blend compositions. The blend exhibited a co-continuous phase morphology in the region of 40 to 60 wt% of ENR-50. Furthermore, the results from dynamic mechanical and dielectric analysis revealed that these blends present a partial miscibility. Finally, the composites based on binary blends of PVDF/ENR-50 containing BT were prepared. The study of the morphologies revealed that BT was dispersed in ENR-50 phase in the case of simple blend. However, the addition of BT after dynamic vulcanization induced localization of BT in PVDF phase and at interface. The highest increment of permittivity can be observed for the composite based on dynamically cured PVDF/ENR-50 (80/20) blend
ศึกษาอิทธิพลของโครงสร้างโมกุลยางธรรมชาติ (NR) และยางธรรมชาติอิพอกไซด์ (ENR) ต่อสมบัติ พบว่าการมีหมู่อิพอกไซด์อยู่ในยาง ENR ทำให้มีการปรับปรุงสมบัติเชิงกล เช่น มอดุลัสและความต้านทานต่อแรงดึง นอกจากนี้สมบัติไดอิเล็กทริกได้แสดงให้เห็นถึงการนำ ไฟฟ้าที่ความถี่ต่ำและอุณหภูมิสูง ยางที่มีหมู่อิพอกไซด์ 50 โมล% (ENR-50) มีค่าการนำไฟฟ้า และค่า permittivity สูงที่สุด ดังนั้นจึงนำยาง ENR-50 ไปใช้ในการเตรียมคอมพอสิตที่ใช้แบเรียม ไททาเนตและเขม่าดำเป็นตัวเติม ซึ่งพบว่าค่า permittivity และค่าการนำไฟฟ้าสูงขึ้นตาม ปริมาณตัวเติมที่ใส่ลงไป ที่ปริมาณ 50%โดยปริมาตรของแบเรียมไททาเนตในยางให้ค่า permittivity สูงถึง 48.7 ในขณะเดียวกันก็พบว่าการเตรียม ENR-50 คอมพอสิตที่ใช้เขม่าดำมี percolation threshold ที่ 6.3 vol% ของเขม่าดำ สำหรับการศึกษาการเปลี่ยนแปลงของสัณฐาน วิทยาและความเข้ากันได้ของพอลิเมอร์เบลนด์ระหว่างพอลิไวนิลลิดีนฟลูออไรด์ (PVDF) กับยาง ENR พบว่า สัณฐานวิทยาของพอลิเมอร์ที่เตรียมได้ขึ้นอยู่กับปริมาณหมู่อิพอกไซด์ในยาง ENR และอัตราส่วนการเบลนด์ อัตราส่วนการเบลนด์ในช่วง 40 ถึง 60% โดยน้ำหนักของยาง ENR- 50 ให้ลักษณะสัณฐานวิทยาแบบวัฏภาคร่วม (co-continuous) นอกจากนี้ผลการทดสอบจาก สมบัติพลวัตเชิงกลและสมบัติไดอิเล็กทริกแสดงให้เห็นถึงความเข้ากันได้บางส่วน (partial miscibility) ท้ายที่สุดนี้ได้เตรียมคอมพอสิตจากพอลิเมอร์เบลนด์ที่เติมแบเรียมไททาเนต สัณฐานวิทยาของคอมโพสิทที่เตรียมได้นั้น พบว่าแบเรียมไททาเนตกระจายตัวในเฟสยางเป็น หลัก อย่างไรก็ตามการเติมแบเรียมไททาเนตหลังจากการวัลคาไนซ์แบบไดนามิกส์ทำให้ แบเรียมไททาเนตกระจายตัวในเฟสพอลิไวนิลลิดีนฟลูออไรด์ (PVDF) และที่ผิวประจัญ (interface) นอกจากนี้คอมพอสิตที่เตรียมจากเทอร์โมพลาสติกวัลคาไนซ์ของ PVDF/ENR 50 ที่ อัตราส่วนการเบลนด์ที่ 80/20 ให้ค่า permittivity ที่สูง
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Ozkoc, Guralp. "Abs/polyamide-6 Blends, Their Short Glass Fiber Composites And Organoclay Based Nanocomposites: Processing And Characterization." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608266/index.pdf.
Full textAbstract:
The objective of this study is to process and characterize the compatibilized blends of
acrylonitrile-butadiene-styrene (ABS) and polyamide-6 (PA6) using olefin based
reactive copolymers and subsequently to utilize this blend as a matrix material in short
glass fiber (SGF) reinforced composites and organoclay based nanocomposites by
applying melt processing technique. In this context, commercially available epoxydized
and maleated olefinic copolymers, ethylene-methyl acrylate-glycidyl methacrylate
(EMA-GMA) and ethylene-n butyl acrylate-carbon monoxide-maleic anhydride
(EnBACO-MAH) were used as compatibilizers at different ratios. Compatibilizing
performance of these two olefinic polymers was investigated through blend
morphologies, thermal and mechanical properties as a function of blend composition and
compatibilizer loading level. Incorporation of compatibilizer resulted in a fine
morphology with reduced dispersed particle size. At 5 % EnBACO-MAH, the toughness
was observed to be the highest among the blends produced.
SGF reinforced ABS and ABS/PA6 blends were prepared with twin screw extrusion.
The effects of SGF concentration and extrusion process conditions on the fiber length
distribution, mechanical properties and morphologies of the composites were examined.
The most compatible organosilane type was designated from interfacial tension and
short beam flexural tests, to promote adhesion of SGF to both ABS and PA6. Increasing
amount of PA6 in the polymer matrix improved the strength, stiffness and also
toughness of the composites. Effects of compatibilizer content and ABS/PA6 ratio on
the morphology and mechanical properties of 30% SGF reinforced ABS/PA6 blends
were investigated. The most striking result of the study was the improvement in the
impact strength of the SGF/ABS/PA6 composite with the additions of compatibilizer.
Melt intercalation method was applied to produce ABS/PA6 blends based organoclay
nanocomposites. The effects of process conditions and material parameters on the
morphology of blends, dispersibility of nanoparticles and mechanical properties were
investigated. To improve mixing, the screws of the extruder were modified. Processing
with co-rotation yielded finer blend morphology than processing with counter-rotation.
Clays were selectively exfoliated in PA6 phase and agglomerated at the interface of
ABS/PA6. High level of exfoliation was obtained with increasing PA6 content and with
screw speed in co-rotation mode. Screw modification improved the dispersion of clay
platelets in the matrix.
26
Facinelli, John Victor. "The preparation of high performance polymers for composites and blends : A) thermally stable ion containing polymers B) epoxy and hydroxy functional polyolefin macromers /." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10192006-115618/.
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Erdogan, Selahattin. "Synthesis Of Liquid Crystalline Copolyesters With Low Melting Temperature For In Situ Composite Applications." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613306/index.pdf.
Full textAbstract:
The objective of this study is to synthesize nematic-thermotropic liquid crystalline polymers (LCP) and determine their possible application areas. In this context, thirty different LCP&rsquos were synthesized and categorized with respect to their fiber formation capacity, melting temperature and mechanical properties. The basic chemical structure of synthesized LCP&rsquo
s were composed of p-acetoxybenzoic acid (p-ABA), m-acetoxybenzoic acid (m-ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA) and isophthalic acid (IPA) and alkyl-diacids monomers. In addition to mentioned monomers, polymers and oligomers were included in the backbone such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) polymers, and polybutylene naphthalate (PBN), polyhexylene naphthalate (PHN) and poly butylene terephthalate (PBT) oligomers that contain different kinds of alkyl-diols. We adjusted the LCP content to have low melting point (180oC-280oC) that is processable with thermoplastics. This was achieved by balancing the amount of linear (para) and angular (meta) groups on the aromatic backbones together with the use of linear hydrocarbon linkages in the random copolymerization (esterification) reaction. LCP species were characterized by the following techniques
Polarized Light Microscopy, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Analysis (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray Scattering (WAXS, Fiber diffraction), surface free energy, end group analysis (CEG), intrinsic viscosity (IV) and tensile test. According to these analysis LCPs were classified into five main categories
(I) fully aromatics, (II) aromatics+ PET/PEN, (III) aromatics + oligomers (IV) aromatics + short aliphatic diacids, (V) aromatics + long aliphatic diacids. The foremost results of the analysis can be given as below. DSC analysis shows that some LCPs are materials that have stable LC mesogens under polarized light microscopy. In TGA analysis LCPs that have film formation capacity passed the thermal stability test up to 390oC. NMR results proved that predicted structures of LCPs from feed charged to the reactor are correct. In FTIR due to the inclusion of new moieties, several peaks were labeled in the finger-print range that belongs to reactants. In X-ray analysis, LCP24 (containing PET) was found to be more crystalline than LCP25 (containing PEN) which is due to the symmetrical configuration. Block segments were more pronounced in wholly aromatic LCP2 than LCP24 that has flexible spacers. Another important finding is that, as the amount of the charge to the reactor increases CEG value increases and molecular weight of the product decreases. Selected group V species were employed as reinforcing agent and mixed with the thermoplastics
acrylonitrile butadiene styrene (ABS), nylon6 (PA6), polyethylene terephthalate (PET), polypropylene (PP) and appropriate compatibilizers in micro compounder and twin screw extruder. The blends of them were tested in dog-bone and/or fiber form. In general LCPs do not improve the mechanical properties except in composite application with polypropylene. A significant increase in tensile properties is observed by LCP24 and LCP25 usage. Capillary rheometer studies show that the viscosity of ABS decreases with the inclusion PA6 and LCP2 together. In addition to the composite applications, some LCPs are promising with new usage areas. Such as nano fibers with 200nm diameter were obtained from LCP27 by electrospinning method. The high dielectric constant of LCP29 has shown that it may have application areas in capacitors.
28
Labaume, Isabelle. "Morphologie et rhéologie de mélanges polyéthylène / polyamide comptabilisés ou chargés de nanoparticules d'argile : mise en évidence et comparaison des propriétés d'interphase." Brest, 2011. http://www.theses.fr/2011BRES2071.
Full textAbstract:
L'objectif est 1/ de contribuer à une meilleure caractérisation de l'interphase, de ses propriétés et de son influence sur la structure et le comportement rhéologique de mélanges polyéthylène/polyamide comptabilisés de manière organique ou par ajout de nano-argiles, 2/ de comparer les propriétés et les effets d'interphase des systèmes comptabilisés de manière organique à ceux des systèmes chargés de nanoparticules argileuses. Ces travaux ont été menés sur quatre couples de mélanges polyéthylène/polyamide, de rapport de viscosités différents, comptabilisés soit par un polyéthylène greffé anhydride maléique, soit chargés de nanoparticules d'argile. L'étude des propriétés d'interphase révèle que, pour les deux types de mélanges ternaires étudiés, les caractéristiques à l'échelle moléculaire du polyéthylène et du polyamide influencent significativement les propriétés viscoélastiques de l'interphase. Un des quatre couples polyéthylène/polyamide conduit à des systèmes ternaires chargés de nanoparticules d'argiles ou comptabilisés par voie chimique présentant des morphologies nodulaires identiques et un effet émulsifiant, autorisant la comparaison des deux types d'interphase. Les résultats montrent que l'interphase argile/polyamide intercalé a des propriétés dissipatives plus marquées que l'interphase obtenue à partir d'une comptabilisation organique. La modélisation des propriétés viscoélastiques des deux types de systèmes ternaires par le modèle de Palierne suggère l'existence de mécanismes de relaxation complexes au sein de ces interphases, impliquant des interactions spécifiques entre les trois composants de ces mélangesThe objective is 1/ to contribute to a better characterization of the interphase, of its properties and of its influence on the structure and rheological behaviour of polyethylene/polyamide blends compatibilized either chemically or physically by addition of nanoclays, 2/ to compare the properties and interphase effects of systems chemically compatibilized with those of systems filled with clay nanoparticles. These works have been performed on four different polyethylene-polyamyde blends, with various viscosity ratio, compatibilized either with a maleic anhydride grafted polyethylene or filled with clay nanoparticules. The study of interphase properties shows that, for the two types of ternary blends studied, the molecular characteristics of polyethylene and polyamide significantly influence the interphase viscoelastic properties. One of the four polyethylene/polyamide couples leads to ternary systems, filled with claynanoparticles or chemically compatibilized, which ewhibit both identical nodular morphology and emulsifying effect, allowing the comparison of the two types of interphase. The results show that the clay/intercalated polyamide interphase has dissipative properties which are more marked than the interphase obtained from a chemical compatibilization. The modeling of the viscoelastic properties of both types of ternary systems, using the Palierne model, suggests the existence of complex relaxation mechanisms within these interphases, involving specific interactions between the three componenets of these blends
29
Hill, Melinda Lou. "Polymeric and Polymer/Inorganic Composite Membranes for Proton Exchange Membrane Fuel Cells." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/37597.
Full textAbstract:
Several types of novel proton exchange membranes which could be used for both direct methanol fuel cells (DMFCs) and hydrogen/air fuel cells were investigated in this work. One of the main challenges for DMFC membranes is high methanol crossover. Nafion, the current perfluorosulfonic acid copolymer benchmark membrane for both DMFCs and hydrogen/air fuel cells, shows very high methanol crossover. Directly copolymerized disulfonated poly(arylene ether sulfone)s copolymers doped with zirconium phosphates and phenyl phosphonates were synthesized and showed a significant reduction in methanol permeability. These copolymer/inorganic nanocomposite hybrid membranes show lower water uptake and conductivity than Nafion and neat poly(arylene ether sulfone)s copolymers, but in some cases have similar or even slightly improved DMFC performance due to the lower methanol permeability. These membranes also show advantages for high temperature applications because of the reinforcing effect of the filler, which helps to maintain the modulus of the membrane, allowing the membrane to maintain proton conductivity even above the hydrated glass transition temperature (Tg) of the copolymer. Sulfonated zirconium phenyl phosphonate additives were also synthesized, and membranes incorporating these materials and disulfonated poly(arylene ether sulfone)s showed promising proton conductivity over a wide range of relative humidities. Single-Tg polymer blend membranes were studied, which incorporated disulfonated poly(arylene ether sulfone) with varied amounts of polybenzimidazole. The polybenzimidazole served to decrease the water uptake and methanol permeability of the membranes, resulting in promising DMFC and hydrogen/air fuel cell performance.Ph. D.
30
Singh, V. B. "Polyethersulphone polymer blends." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37855.
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31
Masson, Jean-François. "Cellulosesynthetic-polymer blends." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74661.
Full textAbstract:
Blends of cellulose (CELL) with polyvinyl pyrrolidone (PVP), poly(4-vinyl pyridine) (P$ sb4$VPy), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), poly($ epsilon$-caprolactone) (PCL), and nylon 6 (Ny6), and of chitosan with PVA were investigated in an attempt to gain some insight into the factors that affect the miscibility of cellulose with synthetic polymers. The miscibility and the scale of mixing of the various blends were studied by differential scanning calorimetry, dynamic mechanical analysis, infrared and NMR spectroscopy, and proton spin-lattice relaxation measurements. The CELL/PVP, CELL/P$ sb4$VPy, and chitosan/PVA blends were shown to be homogeneous at the molecular level, while the CELL/PAN blends were shown to mix on a larger scale. In contrast the CELL/PCL and CELL/Ny6 blends were essentially immiscible; from this it was concluded that the potential for strong inter-molecular interactions is not a sufficient condition for miscibility to occur in cellulose/synthetic-polymer blends.
32
Rosetti, Yann. "Multiscale morphologies of epoxy-based composite matrices from combination of TP-tougheners." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0140.
Full textAbstract:
Les composites stratifiés à matrice organique thermodurcissable (TD) et renforts fibreux continus se sont progressivement imposés dans le monde de l’aéronautique depuis bientôt 50 ans. Ces matériaux, malgré de nombreux avantages ayant permis de remplacer les alliages métalliques précédemment utilisés, ont néanmoins un point faible majeur, à savoir une tolérance aux dommages limitée. De nombreuses solutions de renforcement ont vu le jour, dont l’ajout de polymères thermoplastiques (TP) présentant une ductilité supérieure à la matrice TD. Les travaux réalisés concernent une matrice représentative de composites stratifiés employés aujourd’hui. Elle est constituée d’un système époxy-amine menant à un réseau de haute Tg, ainsi que deux TP utilisés comme agents renforçants : un polyéthersulfone (PES) initialement soluble dans le système, et un polyamide (PA) sous forme de microparticules préformées. Un état de l’art sur les mélanges TD/TP cristallins et l’utilisation de TP comme agents renforçants dans les composites stratifiés est présenté en préambule des résultats expérimentaux. L’étude s’est focalisée sur le comportement de ces deux TP vis-à-vis du réseau époxy-amine en construction lors de la polymérisation. L’intérêt porte sur la compréhension des phénomènes reliant les différents composants du mélange entre eux. Dans un premier temps, le comportement du PES dans le système époxy-amine est étudié en fonction des conditions de polymérisation, à savoir le cycle de température appliqué. Le phénomène de séparation de phase induite par polymérisation (RIPS) ayant lieu étant en compétition avec la gélification du réseau TS, et ces deux phénomènes étant liés à la température, différents types de morphologie ont pu être obtenus. L’approche concernant le PA est différente. En effet, ce polymère initialement insoluble dans le système époxy-amine peut être compatibilisé après avoir réagi avec les monomères époxy. De plus, l’affinité physique entre le PA et le durcisseur aminé employé entraîne une modification du comportement du PA à la fusion. Des systèmes binaires modèles époxy-PA et amine-PA ont donc été étudiés pour bien découpler et comprendre toutes ces interactions. Enfin, les morphologies et propriétés résultantes du système époxy-amine modifié simultanément avec le PES et le PA ont été suivies et contrôlées grâce à un choix pertinent de différents cycles de polymérisation. La compréhension du développement d’un mélange si complexe, en termes de morphologie et de mécanismes réactionnels, a été rendue possible grâce aux études préliminaires sur systèmes modèlesFiber-reinforced thermosetting (TS) matrix-based composites, and more particularly laminates, have progressively imposed themselves in the aeronautic field for nearly 50 years. Nevertheless, despite numerous advantages making them an elegant solution to replace metallic alloys, such composites have a huge drawback: a low damage tolerance. Various toughening solutions have been developed, including the addition of thermoplastic (TP) polymers which exhibit a much higher ductility than the TS matrix. The present work relates on a representative matrix of currently considered laminates. It is constituted of an epoxy-amine system leading to a high Tg network, and two TP used as reinforcing agents: a polyethersulfone (PES) initially soluble in the system, and a polyamide (PA) preformed in micro-particles. A literature review about TS/semi-crystalline TP blends and TP reinforcement agents used in laminates is given previously to the experimental results. The study focuses on the behavior of these two TP in regard to the growing epoxy-amine network during its polymerization. The interest is put in the understanding of the phenomena linking all the matrix components together. In a first time the PES behavior in the epoxy-amine system dependence on curing conditions (i.e. the applied cure schedule) is studied. The reaction-induced phase separation (RIPS) phenomenon being competitive with the TS network gelation, and taking into account that both phenomena are temperature dependent, various types of morphologies were obtained. Apprehension of PA behavior is different. In fact, this polymer is initially soluble in the epoxy-amine system and may be compatibilized after chemical coupling with epoxy prepolymers. Moreover, physical affinities between PA and the considered amine hardener impact the PA melting behavior. Consequently, binary epoxy-PA and amine-PA model systems have been studied to uncouple and understand all these interactions. Finally, resulting morphologies and properties of the epoxy-amine system, simultaneously modified with both PES and PA, have been monitored and controlled thanks to a choice of suitable cure schedules. The understanding of the development of such a complicated system, in terms of morphologies and curing mechanisms, was made possible thanks to the preliminary studies on the model systems
33
Manda, Dimitra. "Thermodynamics of polymer blends." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300415.
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34
Bhutto, Ali Asghar. "Miscibility of polymer blends." Thesis, Brunel University, 1999. http://bura.brunel.ac.uk/handle/2438/7392.
Full textAbstract:
In this work an attempt is made to correlate polymer miscibility with diffusion and with molecular interactions. A system with lower critical solubility temperature has been selected, namely polystyrene (PS) and polyvinyl methyl ether (PVME). Most of the published work has been done on polymers in solutions or on solvent cast specimens and therefore on ternary systems. The role of solvent has not yet been fully evaluated and it was of interest to compare the results on solvent cast samples with those prepared by mechanical blending and by diffusion. Molecular interaction is dependent on functional groups present and for this reason experiments have been performed on PVME blends with PS of different levels of sulfonation (SPS). Selective deuteration (d-PS) was used to identify and assign some absorption peaks in the infrared spectra. DSC measurements have shown that only one Tg is present for all blends prepared by solvent casting. It was necessary to use an extreme quenching rate down to liquid nitrogen in order to preserve the high temperature (above 150°C) phase separated structure, represented by two Tg of homopolymers. The mechanically blended system, on the other hand, did not show a single T g of the blend, unless annealed for one day at 110°C. This confirms the results obtained by diffusion studies using light microscopy and neutron reflectivity, that the diffusion rates are extremely slow and therefore do not control the phase formation and separation processes. These experiments also indicate that the microstructures of solvent cast samples and samples prepared by mechanical blending are different. The Tg of mechanical blended polymers indicate, that the composition of diffusion swollen PS does not correspond to the phase diagram measured in solutions, confirming thus the above result. The FTIR studies at different temperatures have shown that changes in spectra of polymer blends, as reported in the literature can be explained by temperature changes in pure homopolymers. This indicates that molecular interactions, which are responsible for miscibility, are not detectable by infrared absorptions and are therefore of unspecified strength and location. The FTIR of SPSIPVME blends show that sulfonate groups on PS affect polymer miscibility through changes in configuration of molecules, rather than through direct interaction with the PVME, as suggested in the literature. An attempt has been made to study diffusion of SPS and polycarbonate (PC) system by neutron reflectivity. Preliminary results indicate that surface relaxation effects make the data interpretation difficult.
35
Mattsson, Sandra. "Microscopy techniques for studying polymer-polymer blends." Thesis, Umeå universitet, Institutionen för fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-157990.
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Semiconductors are used in many electronic applications, for example diodes, solar cells and transistors. Typically, semiconductors are inorganic materials, such as silicon and gallium arsenide, but lately more research and development has been devoted to organic semiconductors, for example semiconducting polymers. One of the reasons is that polymers can be customized, to a greater extent than inorganic semiconductors, to create a material with desired properties. Often, two polymers are blended to obtain the desired function, but two polymers do not usually result in an even blend. Instead they tend to separate from each other to varying degrees. The morphology of the blend affects the material properties, for example how efficiently it can convert electricity to light. In this project, thin films consisting of polymer blends were examined using microscopy techniques for the purpose of increasing our understanding of the morphology of such blends. One goal was to investigate whether a technique called correlative light and electron microscopy can be useful for examining the morphology of these films. In correlative light and electron microscopy, a light microscope and an electron microscope are used in the same location in order to be able to correlate the information from the two microscopes. The second goal was to learn about the morphology of the thin films using various microscopy techniques. The polymers used were Super Yellow and poly(ethylene oxide) with large molecular weight. Super Yellow is a semiconducting and light-emitting polymer while poly(ethylene oxide) is an isolating and non-emitting polymer that can crystallize. In the blend films, large, seemingly crystalline structures appeared. The structures could be up to 1 mm in the lateral direction, while the films were only approximately 170 nm thick. These structures could grow after the films had dried and their shapes were similar to those of poly(ethylene oxide) crystals. Consequently, there is reason to believe that it is the poly(ethylene oxide) that makes up the seemingly crystalline structures, but the structures also emitted more light than the rest of the film, and Raman spectroscopy showed that there was Super Yellow in the same location as the crystals. Among the microscopy techniques used, phase contrast microscopy was particularly interesting. This method visualizes differences in optical path length and was useful for studying polymer blends when the polymers have different indices of refraction. Correlating light and electron microscopy showed that there was a pronounced topographical difference between the seemingly crystalline regions and the rest of the thin film. Light microscopy has a limited resolution due to diffraction, but as long as the resolution of the light microscope is sufficient for seeing phase separation, correlative light and electron microscopy turned out to be a good method for studying the morphology of thin films of polymer blends.Halvledare är viktiga för många elektroniska ändamål eftersom de kan användas till exempelvis dioder, solceller och transistorer. Traditionellt används inorganiska halvledande material som kisel eller galliumarsenid, men på senare tid har allt mer forskning och utveckling inriktat sig mot organiska (kolbaserade) halvledare, såsom halvledande polymerer, bland annat eftersom det i högre utsträckning går att skräddarsy de organiska materialen så att de får önskvärda egenskaper. Ofta blandas två polymerer med varandra för att skapa ett material med nya egenskaper som är önskvärda, men två polymerer brukar inte blandas jämnt utan tenderar att separera från varandra i olika utsträckning. Hur blandningen ser ut (morfologin) påverkar materialets egenskaper, till exempel hur effektivt det omvandlar ström till ljus. Med syfte att öka förståelsen för hur morfologin ser ut hos en blandning av två polymerer, har detta projekt gått ut på att undersöka tunna filmer av polymer-blandningar med hjälp av mikroskopiska tekniker. Ett delmål var att ta reda på om en teknik som heter korrelativ ljus- och elektronmikroskopi är en bra metod för att undersöka morfologin hos dessa filmer. Vid korrelativ ljus- och elektronmikroskopi används både ett ljusmikroskop och ett elektronmikroskop på samma plats för att kunna korrelera informationen som de båda mikroskopen ger. Det andra delmålet var att undersöka vad de olika mikroskopi-teknikerna kan säga om morfologin hos de tunna filmerna. De polymerer som använts är Super Yellow och poly(etylenoxid) med hög molekylmassa. Super Yellow är en oordnad halvledande och ljusemitterande polymer medan poly(etylenoxid) är en isolerande och icke-emitterande polymer som kan kristallisera. I de blandade filmerna uppstod stora kristall-liknande strukturer som kunde vara upp emot 1 mm breda trots att filmerna bara var ungefär 170 nm tunna. Dessa strukturer kunde växa fram efter det att filmerna redan hade torkat och påminde i form om kristaller som kan bildas av poly(etylenoxid). Det finns alltså skäl att tro att det är poly(etylenoxid) som kristalliserats, men de kristall-liknande strukturerna visade sig emittera mer ljus än vad resten av filmen gjorde, och Raman-spektroskopi visade att det även fanns Super Yellow på samma plats som kristallerna. Bland de mikroskopitekniker som testades utmärker sig faskontrastmikroskopi, som visar skillnader i den optiska vägskillnaden (det vill säga faktisk vägskillnad multiplicerat med brytningsindex). Det visade sig vara en intressant teknik för att studera polymerblandningar när de båda polymererna har olika brytningsindex. Genom att korrelera ljus- och elektronmikroskopi visade det sig att det fanns en tydlig skillnad i struktur mellan de kristall-liknande områdena och resten av den tunna filmen. Ljusmikroskopi har begränsad upplösning på grund av ett fenomen som heter diffraktion, men så länge som ljusmikroskopets upplösning är tillräcklig för att se fasseparation visade det sig att korrelativ ljus- och elektronmikroskopi är en bra metod för att studera morfologin hos tunna filmer av polymerblandningar.
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Julien, Grégoire. "Dynamics in polymer blends and polymer-solvent blends close to the glass transition." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10187/document.
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Dans ce travail, nous proposons un modèle qui décrit la dynamique dans les mélanges de polymères et polymère-solvant à l'approche de la transition vitreuse. Le modèle est résolu sur un réseau 2D sur des échelles de 10 nm à plusieurs microns. Ce modèle incorpore l'aspect hétérogène de la dynamique à l'échelle d'une hétérogénéité dynamique (3-5 nm). Dans le cas des mélanges de polymères, nous appliquons ce modèle afin d'étudier la séparation de phase lorsque le système est refroidi proche ou sous Tg, et le rajeunissement lorsque le système est réchauffé dans un état miscible et fondu. Pendant la séparation de phase, nous observons que des morphologies lentes se forment en coexistence avec des morphologies rapides. Pendant ce temps, la dynamique globale du système se ralentit et les domaines croissent comme le logarithme du temps. Lors de la réchauffe en revanche, nous observons que les domaines vitreux fondent plus vite que le temps nécessaire pour qu'ils se forment lors de la séparation de phase. Dans le cas des mélanges polymère-solvant, le système est en contact avec un réservoir de solvant et est en dessous de la température de transition vitreuse du polymère pur. L'activité du réservoir peut être changée afin de décrire le séchage ou le gonflement de films. Notre modèle permet de décrire la diffusion cas-II lorsqu'un polymère vitreux est plastifié par du solvant qui pénètre le système. Concernant le processus inverse de séchage, nous montrons que des films ayant des épaisseurs inférieures à 1 micron peuvent être séchés entièrement. Pour des films plus épais, en revanche, une croûte vitreuse se forme sur la surface libre du filmIn this work, we propose a model for describing the dynamics in polymer blends or polymer-solvent blends close to and below Tg. The model is solved on a 2D lattice corresponding to spatial scales from 10 nm up to a few micrometers and incorporate the heterogeneous nature of the dynamics at the scale of a dynamic heterogeneity (3-5 nm). In case of polymer blends, we apply this model to study phase separation close to and below Tg upon cooling, and rejuvenation in miscible range upon heating. In the course of phase separation, we observe slow structures forming in coexistence with faster ones. In the same time, the global dynamics of the system slows down and domains grow like the logarithm of the time. During rejuvenation, we observe that morphologies melt much faster the elapsed time required to build them during aging. In the case of polymer-solvent blends, the system is put in contact with a solvent reservoir and is at temperatures far below the pure polymer glass transition. We consider situations where the activity of the solvent reservoir is varied in order to describe either films drying or swelling. Our model allows for explaining case-II diffusion in the context of the plasticisation of a glassy polymer by penetrating solvent during swelling. Regarding the process of film drying, we show that films up to 1 micrometer thick can be completely dried. When drying a thicker film, we show that a glassy crust may appear on the free surface, as shown experimentally
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Huynh, Anh Nhut Materials Science & Engineering Faculty of Science UNSW. "Rubber-polymer blends: a thesis in polymer engineering." Awarded by:University of New South Wales. Materials Science & Engineering, 2007. http://handle.unsw.edu.au/1959.4/40833.
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This study examines composite materials prepared from ground recycled tires (tire crumb) and post-consumer recycled high density polyethylene (HDPE). An initial set of composites was prepared from as-received tire crumb and HDPE recyclate containing 040% tire crumb in 10% increments, using injection moulding. The elastic modulus and tensile strength were found to decrease linearly with increasing tire crumb content. Addition of tire crumb to recycled HDPE caused produced an immediate reduction in the strain to failure with a progressively more modest decrease as the tire crumb content was increased. The impact toughness decreased more linearly with increasing tire crumb fraction. Cross sections of the composites showed that the tire crumb particles were in intimate contact with the matrix but post mortem examination of the fracture surface of the impact test specimens indicated that the level of bonding had been poor. A second set of composites was a prepared from 10% tire crumb. The tire crumb was first given an oxidative treatment in hot aqueous copper chloride at concentrations from 0-5 wt% Cu Ch at 50 or 100??C for 6 or 12 hours. The composites were injection moulded with an addition of 0.5 wt% dicumyl peroxide (DCP). These composites showed good bonding between the tire crumb and the recycled HDPE even at concentrations of 0% of the Cu 2+ oxidation catalyst. The addition of DCP was found to substantially reduce the modulus of neat HDPE and this reduction was reflected in the modulus of the composites. It was found that the DCP concentration could be reduced to 0.02% without adversely affecting the composites.
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Milner, V. A. "Miscibility predictions in polymer blends." Thesis, Lancaster University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332385.
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Clark, Jane Northen. "Intermolecular interactions in polymer blends." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47811.
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Gamini, Seneviratne Weerasekara Mudiyanselage. "Phase separation of polymer blends." Thesis, University of Sussex, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293398.
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Jackson, Stuart Thomas. "Surface analysis of polymer blends." Thesis, University of Sheffield, 1993. http://etheses.whiterose.ac.uk/14740/.
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Cordi, Livia. "Estudo da biodegradação dos filmes de poli (e-caprolactona), da blenda poli (e-caprolactona)/amido e do composito poli (e-caprolactona)/amido/po de fibra de coco por fungos e bacterias." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267251.
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Orientadores: Lucia Helena Innocentini Mei, Nelson Eduardo Duran CaballeroDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Imensurável é a quantidade de resíduos plásticos descartados no meio ambiente e o crescente desequilíbrio do mesmo. Esta situação leva ao desenvolvimento de novas formulações plásticas que sejam resistentes e funcionais enquanto em uso, mas que após o período de interesse sejam degradados no menor período de tempo possível. Com o intuito de minimizarmos as quantidades de polímeros descartados no meio ambiente, dentro de uma perspectiva de desenvolvimento sustentável e diminuindo a poluição ambiental, estudamos a aplicação de fungos e bactérias isolados de solo para reduzir o tempo de degradação de polímeros considerados biodegradáveis. Para isto, foi preparada e caracterizada uma blenda composta por Poli (e- caprolactona) e Amido de milho adipatado e também um compósito de Poli (e- caprolactona), Amido de milho adipatado e pó de fibra de coco, visando assim obter um material com alta taxa de biodegradação. A caracterização e o acompanhamento da biodegradação do filme de PCL, da blenda PCL/amido e do compósito PCL/amido/fibra de coco foi feita por Análise Visual, Perda de Massa, Espectroscopia no Infra-Vermelho Próximo (NIR), Análise Termogravimétrica (TGA), Microscopia Eletrônica de Varredura (MEV), Microscopia de Força Atômica (AFM) e Análise de Componentes Principais (PCA). Os resultados obtidos pela biodegradação promovida por bactérias extraídas de solo foram de 54% de perda de massa para a blenda de PCL/amido e de 47% para o filme de PCL em 100 dias. A taxa de biodegradação para o PCL, independente do fungo utilizado é muito baixa para o período de 60 dias, não superando os 5% de perda de massa. O fungo F. moniliforme reduziu a massa da blenda PCL/amido em 22,5% no mesmo período em que a espécie F. oxysporum não apresentou mais que 10% de perda de massa para o mesmo material. Para a biodegradação dos compósitos PCL/amido/fibra de coco os resultados de perda de massa indicam que o aumento da porcentagem de fibra de coco leva a um aumento da biodegradação.
Abstract: Hugh amount of plastic waste is discarded in the environment causing a growing imbalance. This situation leads to the development of new resistant and functional plastic materials to last during their useful life and biodegrade after it, in a short period of time. In order to minimize the quantity of polymers discarded in the environment, within a perspective of sustainable development and reducing environmental pollution, we studied the application of fungi and bacteria isolated from soil to reduce the time of degradation of polymers considered biodegradable. For this, a blend composed of Poly (e-caprolactone) and maize starch adipate and also a composite of Poly (e-caprolactone/maize starch adipate/powder fibers from coconut has been prepared and characterized, seeking thereby to obtain a material with a high rate of biodegradation. The characterization and monitoring of the degradation of the PCL film, the PCL/starch blend and the composite PCL/starch/coconut fiber was made by Visual Analysis, Mass Loss, Near Infra-Red Spectroscopy(NIR), Thermogravimetric analysis (TGA ), Electronic Scanning Microscopy (SEM), Atomic Force Microscopy (AFM) and Principal Components Analysis (PCA). The results obtained in 100 days for the biodegradation promoted by bacteria isolated from soil were 54% of weight loss for PCL/starch blend and 47% of weight loss for PCL film. The rate of biodegradation for the PCL, regardless of the fungus used is very low for the period of 60 days, not exceeding 5% of the weight loss. The fungus F. Moniliforme reduced the mass of PCL / starch blend to 22.5% in the same period in which the species F. oxysporum not presented more than 10% of weight loss for the same material. For the biodegradation of PCL / starch / coconut fiber composites, the results of weight loss indicate that the increase in the percentage of coconut fiber leads to an increase in the degradation rate.
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química
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Jones, R. A. L. "Mutual diffusion in miscible polymer blends." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233254.
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Recent theories have suggested that mutual diffusion between miscible polymers may be strongly influenced by the unusual thermodynamics of mixing of high polymers; in addition the mobility properties of polymer blends are not, in general well understood. This dissertation describes experiments to investigate how these factors influence mutual diffusion in miscible polymer blends. After a general introduction and a review of some recent theories of mutual diffusion in polymer blends, experiments are described in one miscible blend system, Polyvinyl Chloride (PVC)/Polycaprolactone (PCL);x-ray microanalysis in a scanning electron microscope was used to measure the concentration dependence of the mutual diffusion coefficient. To explain this concentration dependence we need to invoke not only the thermodynamics of mixing but also the dependence on composition of the monometric friction coefficients in the system. This dependence was investigated using an ESR spin probe technique. The final section of the dissertation deals with an attempt to use the potentially powerful ion beam analysis techniques of Rutherford Backscattering (RBS) and Forward Recoil scattering (FReS) to measure mutual diffusion coefficients, as well as intradiffusion coefficients (whose concentration dependence should not be influenced by thermodynamic effects). Results obtained by these techniques are presented for three blend systems, including PVC/PCL; the results by RBS for the latter system are consistent with the results obtained by x-ray microanalysis.
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Muangpil, Sairoong. "Functionalised polymers and nanoparticle/polymer blends." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654111.
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The incorporation of nanoparticles into polydimethylsiloxane polymers either in the form of physical blending or chemical crosslinking has long been studied as it can improve the properties of composite materials. Interactions between the host polymer and the filler particle, filler concentration and conformation of each component are the key factors that influence these properties. Understanding the effect of these factors is of fundamental importance in all practical applications of composite materials. This thesis describes the study of a range of PDMS composites by using a variety of experimental techniques. The main techniques used were spin-spin (T2) relaxation and diffusion NMR spectroscopy, rheology and small-angle neutron scattering (SANS). The molecular mobility of a series of PDMS melts has been studied for both unentangled and entangled molecular weight regimes separated by the critical entanglement molecular weight (Mc) of the polymer. The experimental results revealed the effect of molecular weight and polydispersity of the polymers on their segmental mobility. The dramatic decrease of chain mobility observed at molecular weight above Mc was attributed to the effect of chain entanglements. The effect of nano-sized trimethylsilylated polysilicate resin (R2) on the chain mobility of PDMS in the form of physically blended was also examined. Two different concentrations (17 and 30 vol%) of R2 were incorporated into a wide range molecular weight of PDMS melts. Below Mc, the R2 particle was found to reinforce the PDMS at all particle loadings, whereas a plasticisation effect was observed for high molecular weight PDMS above Mc. This was attributed to a reduction of the degree of the entanglements when polymer chains adsorbed on particles. Chemically bonded composites of PDMS and polyhedral oligomeric silsesquioxane (POSS) were successfully synthesised via hydrosilylation. The length of the PDMS central block was found to affect both the size and the molecular mobility of the triblock polymers. The weight fraction of POSS and substituted groups on POSS were also seen to affect the molecular mobility. Finally, a series ofrandom crosslink polymer films ofPDMS and phenylsilsesquioxane (TPh) was studied by AFM, TEM, SAXS and SANS techniques to investigate the factors influencing the optical clarity of the samples. The degree of swelling and the segmental mobility of the sample films swollen in good and poor solvents were also studied.
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El-Begawy, Salah El-Din Moustafa. "Miscibility in polymer blends during copolymerization." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305127.
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Morley, Kevin P. "Criteria of failure for polymer blends." Thesis, Manchester Metropolitan University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303218.
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Webb, W. D. "Gas transport in miscible polymer blends." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37890.
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Słota-Newson, Joanne Elizabeth. "Diblock compatibilizers in optoelectronic polymer blends." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610183.
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Deb, Nabankur. "Morphological studies in polymer-fullerene blends." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54381.
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Polymer-fullerene blend systems have found relevance and application in a number of fields including organic photovoltaic devices. While synthesizing new materials with desirable electronic properties is essential to designing better photovoltaic devices, it is equally important to understand the complex phase morphology of these blends and its effect on device performance. Consequently, this knowledge could be used to further design new materials and device architecture for more efficient systems. In particular, this dissertation focuses primarily on the morphology in a series of amorphous as well as semi-crystalline polymer-fullerene blend systems both in bulk and thin films and its relation to device performance. Scattering based techniques have been used to determine in-plane and out-of-plane phase morphology. Morphological parameters derived from these studies have shown possible correlation between fullerene segregation and device performance values. The results of these studies have been used to synthesize a thermo-cross-linkable fullerene acceptor having slower diffusion through the polymer, allowing better control of the polymer-fullerene blend morphology. Consequent effects have been studied on device lifetime and thermal stability and have shown significant improvements
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Robertson, Christopher G. "Physical Aging of Miscible Polymer Blends." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/40427.
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Physical aging measurements were performed on various polymeric glasses with the overriding goal of developing a better molecular picture of the nonequilibrium glassy state. To this end, aging-induced changes in mechanical properties and in the thermodynamic state (volume and enthalpy) were assessed for two different miscible polymer blends as a function of both composition and aging temperature. This investigation considered the physical aging behavior of blends containing atactic polystyrene (a-PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as well as mixtures of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). Substantial attractive chemical interactions are characteristic of a-PS/PPO blends but are absent in PMMA/SAN blends. The distinct nature of interactions for these two blends resulted in differences in the compositional dependence of secondary relaxation intensity, segmental cooperativity which dictates glass formation kinetics, and density (prior to aging). The variation of volume relaxation rate with aging temperature and composition was interpreted based upon these characteristics for the two systems. In addition, a general relationship was uncovered which linked structural relaxation rates for amorphous polymers to their respective segmental relaxation characteristics (glass transition cooperativity or fragility), which in turn are well understood from a molecular standpoint. This work, therefore, established a basis for comprehending glassy state volume and enthalpy relaxation rates based upon molecular characteristics. Developing an understanding of the connection between the evolving thermodynamic state and mechanical property changes fared less well. The fact that the thermodynamic and mechanical properties can have very different relaxation time responses governing their changes in the nonequilibrium glassy state was clearly evident in an extensive study of the physical aging characteristics of an amorphous polyimide material. For some materials, interpretation of mechanical aging behavior was obscured by thermorheological complexity arising due to overlap of a secondary relaxation with the main chain softening dispersion.Ph. D.