Дисертації з теми "Thermoplastic elastomer characterization"

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.
Includes bibliographical references.
Segmented polyurethane elastomers containing additional ordered structures within the hard or soft domains were developed to mimic the hierarchical structure and superior properties observed in spider silk fibers. The silk's toughness is related to a fiber morphology that includes P-pleated crystalline sheets within an amorphous matrix, as well as an additional interphase with an orientation and mobility between that of the two microphases. In the polyurethane mimics, bulky aromatic diisocyanates were incorporated between aliphatic hexamethylene diisocyanate (HDI) hard segments and poly(tetramethylene oxide) (PTMO) soft segments, to enhance the size and orientation of the interphase. The mixture of diisocyanates reduces the crystallinity of the HDI hard segments, allowing the polyurethane to form more well-organized domains observed by AFM imaging. The more interconnected hard domains allow the elastomers to deform to higher elongations and absorb more energy without a decrease of initial modulus. Shearing of the hydrogen-bonded hard domains orients the hard blocks at a preferred tilt angle of ±20⁰ from the strain direction during tensile deformation.
(cont.) While the average spacing of hard domains increases during deformation, the spacing of hard domains aligned with the strain decreases, and the spacing of hard domains at the preferred tilt angle remains constant. Strain-induced crystallization of the PTMO soft segments was observed in all samples; however, hard segments with mixed diisocyanates exhibited non-crystalline alignment of the hard domains. Several polyurethane nanocomposite structures were also created using particles that preferentially associate with hard or soft segments. HDI-PTMO polyurethane/Laponite nanocomposites provided modest mechanical property improvements (80% increase in modulus and 15% increase in toughness) without any loss of extensibility. The Laponite discs exhibited an exfoliated structure, associating with and reinforcing the hydrophilic polyurethane hard segments. HDI-PTMO polyurethane/MQ siloxane resin nanocomposites also exhibited particle association with the hard segments, providing a 60% increase in modulus with a small loss of toughness.
(cont.) However, composites of isobutyl-POSS dispersed in polyurethanes with mixed hard segments exhibited formation of POSS crystals associated with the soft segments at all loadings, resulting in tensile failure at strains 80-100% lower than the pure polyurethane.
by Gregory Stewart Pollock.
Ph.D.

Ce travail de doctorat est consacré à la production et à la caractérisation de composés polymères à base de matrices thermoplastiques en mélange avec des particules de caoutchoucs recyclés. Les principales applications visées sont: (A) la production d’élastomères thermoplastiques (TPE) à haute teneur (50% et plus) en poudrette de caoutchouc de pneus usés (GTR); et (B) l’amélioration de la résistance à l’impact des composites thermoplastiques avec de faibles concentrations en GTR. Dans la première partie de ce travail, du polyéthylène maléaté (MAPE) a été utilisé comme matrice pour produire des mélanges MAPE/GTR présentant d'excellentes caractéristiques en tant qu’élastomère thermoplastique. Puis, les effets de différents mécanismes de dégradation (humidité, chaleur et recyclage) sur les propriétés des composites MAPE/GTR ont été largement examinés afin d’évaluer le potentiel de ces matériaux après plusieurs cycles d’utilisation. Enfin, le renforcement des TPE/GTR par différentes particules solides (poudre de bois et talc) a été étudié pour des applications plus exigeantes (caractéristiques mécaniques). Dans la seconde partie de ce travail, une nouvelle approche est proposée pour la modification de la résistance aux chocs des composites à base de polypropylène renforcé par des charges organique (chanvre) et inorganiques (talc, verre). L’amélioration des propriétés à l'impact de ces composites a été réalisée par l’addition d’un mélange à base de polypropylène maléaté (MAPP) et de poudrette de caoutchouc (GTR et déchets d’EPDM) contenant des concentrations élevées (jusqu’à 70% en poids) de déchets caoutchoutiques.
This Ph.D. work is devoted to the production and characterization of polymer compounds based on thermoplastic matrix filled with waste rubber powder. The main applications include: (A) the production of thermoplastic elastomer (TPE) resins containing high ground tire rubber (GTR) contents (50% and higher), and (B) impact modification of thermoplastic composites using low concentrations of GTR. In the first part of the work, maleated polyethylene (MAPE) is proposed as a matrix to produce MAPE/GTR blends having excellent characteristics as thermoplastic elastomers. Then, the effects of different degradation mechanisms (weathering, thermal degradation and reprocessing) on the properties of MAPE/GTR compounds were extensively investigated to determine their potential for further recycling. Finally, the reinforcement of GTR filled TPE was investigated using different types of solid particles (wood flour and talc) for more demanding applications (mechanical characteristics). In the second part of the work, a new approach is proposed for impact modification of polypropylene based composites based on organic (hemp) and inorganic (talc and glass) reinforcements. The effective improvement of the impact properties of these composites is performed through the addition of a masterbatch based on maleated polypropylene (MAPP)/waste rubber powder (GTR or waste EPDM) containing high concentrations (70% by weight) of waste rubber.

In this thesis, the effect of interphase bonding on the cohesiveness of domain structure was addressed. The interchain attractive forces between rigid segments and the phase separation between hard and soft segments have been improved by introducing either urea groups or ionic units. The urea linkages have the possibility of extensive hydrogen bonding while ionic units interact with each other by coulombic interactions, which provide even stronger interchain associations than the hydrogen bonding effects. This thesis addressed the preparation and characterization of polytetrahydrofuran based segmented polyurethane-urea and ionene elastomers. The urea linkages were effectively introduced to the polyurethane elastomers through an unconventional route which was based on carbamate-isocyanate interactions. The carbamates were generated principally from isocyanate functional prepolymers and tertiary alcohols. The carbamates were rearranged thermally and/or catalytically to produce amines which were rapidly converted to ureas. The effects of varying the size of the rigid and flexible segments in polyurethane elastomers on physical behavior were investigated. The importance of hydrogen bonding interactions in promoting phase separation of hard and soft segments and the cohesiveness of hard segment domain structure was demonstrated. Living, difunctional polytetrahydrofuran dioxonium ions were prepared via triflic anhydride initiation. The direct coupling of these "living" polytetrahydrofuran dioxonium ions with a ditertiary amine was used to produce a novel segmented ionene elastomer. The ionenes thus synthesized displayed interesting solution behavior and could be molded, or cast to produce good physical properties. Photochromic as well as thermochromic phenomena were also noticed in these systems.
Ph. D.

Polymers containing poly(1,3-cyclohexadiene) were synthesized using a novel pre-formed initiator comprised of an alkyllithium and a tertiary diamine. The use of a pre-formed intiator at moderate temperatures (25° C) enabled the synthesis of high molecular weight poly(1,3-cyclohexadiene) homopolymers ( = 50000) with narrow molecular weight distributions (/ = 1.20). In contrast, the use of a conventional anionic initiation approach resulted in polymerizations that lacked significant degrees of livingness, which limited the polymer molecular weights to approximately 10000. Use of the preformed initiator resulted in a reduction in the degree of both chain termination and chain transfer. In addition, the livingness of the polymerization was shown to be a function of the monomer concentration and the polymerization temperature. The regiochemistry of the polymers were shown to be dependent on the tertiary amine used in the polymerization, which provided a route for the synthesis of polymers with a microstructure rich in either high 1,2-addition (70%) or high 1,4-addition (90%). A range of analytical methods were employed to determine the stereo and regiochemistry of poly(1,3-cyclohexadiene). These methods included 1H NMR, 13C NMR, and endgroup functionalization of the propagating center with chlorotrimethylsilane. The impact of regiochemistry on the thermal properties was examined using differential scanning calorimetry. In addition, the thermooxidative properties of these poly(1,3-cyclohexadiene) polymers were characterized in a series of oxidative studies and the onset of oxidative degradation occurred at 110° C. Perfectly alternating copolymers of poly(1,3-cyclohexadiene-alt-styrene) were synthesized, and the reactivity ratios for these copolymers (r1,3CHD = 0.022, rstyrene = 0.024) were determined using a conventional Mayo-Lewis approach. The effect of aromatization and hydrogenation on the thermal properties of these copolymers was determined using thermal gravimetric analysis and differential scanning calorimetry. The synthesis of poly(1,3-cyclohexadiene) DVB coupled star-shaped polymers was performed using a convergent arm-first approach in combination with a divinylbenzene coupling agent (PDI = 1.25). Well-defined poly(1,3-cyclohexadiene-block-isoprene)-star shaped polymers were synthesized and utilized for the development of novel high temperature thermoplastic elastomers, with excellent elastomeric properties (percent elongation = 745 %, tensile strength = 7.2 MPa). Atomic force microscopy in combination with differential scanning calorimetry verified the presence of microphase separation between the blocks.
Ph. D.

La réparation endovasculaire (EVAR) d'un anévrisme de l'aorte abdominale (AAA) consiste en la mise en place d'une endoprothèse (EDP) par chirurgie mini-invasive au sein de l'anévrisme. Cet acte permet de prévenir la rupture des tissus endommagés impliqués dans un AAA, défini comme la dilatation localisée du diamètre de l'aorte. Lorsque l'amont de l'anévrisme englobe les artères périphériques rénales et/ou viscérales, l'AAA est qualifié de complexe. Dans ce cas, l'EDP déployée est dite « fenêtrée », en d'autres termes, perforée à l'emplacement des jonctions vers les artères périphériques. La prise en charge dans le cadre d'un AAA complexe devient alors plus limitante car l'EDP fenêtrée sera conçue sur mesure afin de correspondre à l'anatomie de l'anévrisme et à la position des artères périphériques du patient. Cela implique un délai de fabrication de plusieurs semaines, limite la prise en charge aux anévrismes stables et exclut les situations d'urgence. Dans ce contexte, l'impression 3D présente un intérêt considérable pour la fabrication d'EDP sur mesure et dans des délais très courts. Ainsi, l'objectif de ce travail de thèse est de concevoir un prototype d'endoprothèse par impression 3D d'un polyuréthane thermoplastique (TPU) de grade médical (élastomère thermoplastique). Le présent travail permettra de valider le procédé de conception et la fonctionnalité de notre 3D-EDP pour son application finale en tant que dispositif médical implantable.Dans un premier temps, l'impact du procédé de fabrication sur les propriétés chimiques, physiques et physico-chimiques du TPU a été étudié à chaque étape, des granulés à la stérilisation par rayons gamma d'une prothèse fabriquée par dépôt de filament fondu (FDM). L'évaluation préliminaire in vitro de la cytotoxicité et de l'hémocompatibilité du TPU a été réalisée après l'étape d'impression 3D et de stérilisation. Un vieillissement préliminaire du TPU en conditions oxydantes extrêmes a été réalisé afin de prédire l'évolution de ses propriétés sur le long terme. Par la suite, une stratégie de conception d'un prototype implantable par voie endovasculaire a été développée. Les propriétés de ce prototype stérilisé ont été caractérisées par différentes techniques (CES, ATG, DSC, FTIR, MEB, goniométrie, traction uniaxiale, …). Ses propriétés biologiques ont été évaluées in vitro par des tests de cytocompatibilité, hémocompatibilité et contact avec les macrophages pendant 24 heures (inflammation aigüe). L'évolution de ses propriétés physico-chimiques et mécaniques a été suivie par des études de vieillissement in vitro.La caractérisation des propriétés chimiques, physiques et physico-chimiques du TPU a montré que l'impression 3D FDM et la méthode de stérilisation par rayons gamma constituent une voie de fabrication viable d'un prototype comprimable dans un cathéter d'introduction endovasculaire. L'évaluation biologique in vitro a montré la cytotocompatibilité du prototype par la méthode de l'extrait. De plus, le prototype s'est révélé faiblement hémolytique et les plaquettes adhérant à sa surface n'étaient pas activées. La faible sécrétion de cytokines (IL-6 et TNF-a) au contact des macrophages inactivés a montré que le prototype d'EDP ne présente pas de caractère pro-inflammatoire. Enfin, les études de vieillissement ont montré un impact sur les propriétés mécaniques et de surface de notre prototype d'EDP sans toutefois compromettre sa fonctionnalité. Par la suite, la stratégie de conception pourrait évoluer vers une fonctionnalisation de l'EDP afin de prévenir les infections et les thromboses responsables respectivement de 2% et 6% des complications post-opératoires
Endovascular repair (EVAR) of an abdominal aortic aneurysm (AAA) involves the placement into the aneurysm of a stent graft (SG) by minimally invasive surgery. This procedure prevents rupture of the damaged tissue involved in an AAA, defined as a localized diameter dilation of the aorta. When the upstream portion of the aneurysm includes the peripheral renal and/or visceral arteries, the AAA is qualified as complex. In this case, the deployed SG is said “fenestrated”, in other words, perforated at the site of junctions to the peripheral arteries. Management of a complex AAA becomes more limiting as the fenestrated SG will be custom designed to match the anatomy of the aneurysm and the position of the peripheral arteries of the patient. This implies a manufacturing delay of several weeks, limits the management to stable aneurysms and excludes emergency situations. In this context, 3D printing (3DP) is of considerable interest for the fabrication of custom-made SGs in a very short time frame. Thus, the objective of this thesis work is to design a SG prototype by 3D printing of a medical grade thermoplastic polyurethane (TPU) (thermoplastic elastomer). The present work will validate the manufacturing process and the functionality of our 3DP-SG for its final application as an implantable medical device.First, the impact of the manufacturing process on the chemical, physical and physicochemical properties of TPU was studied at each step, from the pellets to the gamma-ray sterilization of a graft manufactured by fused filament deposition (FDM). In vitro preliminary evaluation of the cytotoxicity and hemocompatibility of TPU was carried out after the 3D printing and sterilization step. Aging of TPU under extreme oxidizing conditions was performed to predict the evolution of its properties in the long term. Subsequently, a design strategy for an endovascular implantable prototype was developed. The properties of said prototype were characterized by different techniques (SEC, TGA, DSC, FTIR, SEM, goniometry, uniaxial traction, ...). Its biological properties were evaluated in vitro by tests of cytocompatibility, hemocompatibility and contact with macrophages for 24 hours (acute inflammation). Moreover, the evolution of its physicochemical and mechanical properties was evaluated by in vitro aging studies.The characterization of the chemical, physical and physicochemical properties of TPU enabled the validation of a FDM printing manufacturing route and gamma ray sterilization of a crimpable SG prototype. The in vitro biological evaluation showed the non-cytotoxicity of the SG prototype by the extraction method. Moreover, the prototype was found to be weakly hemolytic and the platelets adhered on its surface were not activated. The low secretion of cytokines (IL-6 and TNF-α) upon contact with inactivated macrophages showed that the SG prototype does not exhibit a pro-inflammatory characteristic. Finally, aging studies showed an impact on the mechanical and surface properties of our SG prototype without compromising its functionality. Subsequently, the design strategy could evolve towards a functionalization of the SG prototype in order to prevent infections and thrombosis responsible for 2% and 6% of postoperative complications respectively

The advancement of each component of aerospace vehicles is necessary as the continual demand for more aggressive missions are created. Improvements in propulsion and guidance system electronics are invaluable; however without material development to protect the vehicle from its environment those advances will not have a practical application. Thermal protection systems (TPS) are required in both external applications; for example on reentry vehicles, as well as in internal applications; to protect the casing of rockets and missiles. This dissertation focuses on a specific type of internal solid rocket motor TPS, ablatives. Ablatives have been used for decades on aerospace vehicles. To protect the motor from the hostile environment, these materials pyrolyze and char. Both of these mechanisms produce a boundary between the combustion gases and the motor as well as release the heat that the decomposed material has absorbed. These sacrificial materials are intended to protect the casing that it is attached to. With the development of polymer nanocomposites (PNCs) in the last couple of decades, it is of interest to see how these two fields can merge. Three different nanomaterials (carbon nanofibers, multiwall carbon nanotubes, and nanoclays) are examined to observe how each behaves in environments that simulate the motor firing conditions. These nanomaterials are individually added to a thermoplastic polyurethane elastomer (TPU) at different loadings, creating three distinct families of polymer nanocomposites. To describe a materials ablative performance, a number of material properties must be individually studied; such as thermal, density, porosity, char strength, and rheology. Different experiments are conducted to isolate specific ablative processes in order to identify how each nanomaterial affects the ablative performance. This dissertation first describes each material and the ablative processes which are characterized by each experiment. Then basic material properties of each family of materials are described. Degradation and flammability experiments then describe the degassing processes. Studies of the material char are then performed after full blown rocket experiments are done. These tests have shown that of the three nanomaterials, nanoclay enhances the TPU ablative performance the most while the CNF provides the least enhancement.
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碩士
臺北醫學大學
口腔科學研究所
94
As a vertical compaction root canal filling material, gutta-percha suffered from many disadvantages, such as dimensional contraction during cooling, possible thermal degradation due to the overheating when down packing, and requirement of tedious operational procedures. As such, this study used thermoplastic elastomer, Engage, as base material, Graphite and ZnO as functional fillers, and thermally blended these ingredients at different composition to produce composite materials. Thermal conductivity, melt viscosity, dimensional stability and thermal stability of the resulted materials were measured by Hot Disk Thermal Constants Analyzer, Advanced Rheometer, and Thermal Mechanical Analyzer, Thermal Gravimetric Analyzer. The results show the addition of inorganic compounds enhanced the overall thermal conductivity of the composite materials. Among the fillers, graphite had better result on the thermal conductivity. In some cases, the thermal conductivity was 2 to 3 times higher than that of the GP. With increasing of the inorganic fillers/Engage ratio, the viscosity of the composite material increased and came close to that of Real Seal. However, it is still much less than that of GP, indicating the possible easy of operation of the new materials. Addition of the graphite and zinc oxide enhanced the overall thermal stability of the composite material by more than 100oC, comparing to those of GP and Real Seal. The dimensional stability was improved as the addition of inorganic compounds.

Dissertação de mestrado (área de especialização em Processamento e Caracterização de Materiais)
Os Termoplásticos elastómeros, TPEs, têm vindo a substituir os tradicionais elastómeros devido à sua elevada eficiência mecânica, à sua alta processabilidade e baixo custo. Numa gama cada vez mais alargada de aplicações (p.e., nas indústrias automóvel e militar, componentes médicos, electrónica, construção civil, etc.) as exigências aumentam, assim como a necessidade de materiais com propriedades melhoradas. A mistura de um polímero com um outro material dá origem a um novo sistema polimérico com propriedades melhoradas, resultante da combinação das propriedades existentes. A incorporação de reforços no TPE poderá adicionar-lhe novas funcionalidades e apresentar melhoramentos quanto ao seu desempenho. Os compósitos de TPEs a estudar, incorporarão reforços de escala micro e nanométrica. Dois tipos de TPEs serão considerados pela sua natureza: amorfoamorfo (p.e. SBS) e amorfo-semicristalino (p.e. TPU). Isto permitirá induzir diferentes estados morfológicos e investigar a relevância das interacções interfásicas. Reforços como negro de fumo, nanofibras de carbono, nanosilica, nanoclays e vermiculites têm despertado grande interesse pelas propriedades que exibem. A combinação destes com os TPE pode resultar em materiais com melhores propriedades e “inteligentes” que podem ser integrados em sistemas como sensores/controladores de deformação ou força, temperatura, etc. O desenvolvimento destes compósitos requer um certo knowhow. Não é certo que adição destes reforços irá conferir as funcionalidades desejadas, mais ainda quando feito com percentagens de incorporação muitos baixas e de difícil dispersão. Será um compromisso entre vários critérios que influenciarão desde a sua processabilidade, o seu comportamento mecânico e a sua estabilidade a longo prazo. Este trabalho tem como principal objectivo caracterizar e compreender o comportamento (mecânico, térmico, eléctrico e ao fogo) dos TPEs carregados com partículas micro e nanométricas.
Thermoplastic elastomers, TPEs, have been used to replace the traditional elastomers due to their high mechanical efficiency, easy processabillity and low cost. In an increasingly broad range of applications (e.g., automobile industry and military, medical component, electronics, civil construction, etc.), the demands increases as well as the need for materials with improved and multifunctional properties. The combination of a polymer with a filler gives rise to a new polymer system with improved performance and added functionalities as a result of the combination of the existing properties. The TPE’s composites selected for this study will incorporate micro- and nanometric scale reinforcements. Two types of TPEs will be considered for their nature: amorphous-amorphous (e.g. SBS) and amorphous-semicrystalline (e.g. TPU). This will lead to induce different morphological states and investigate the relevance of interfaces interactions. Reinforcements such as carbon black, carbon nanofibers, nanosilica, nanoclays and vermiculites (VC) have attracted great interest due to the properties that they exhibit. The combination of these materials with the TPE may result in high performance and “intelligent” materials, ideal to be integrated in systems like deformability or temperature sensors/controllers, that are able to adapt and response in different applications depending on environmental changes, among others. The development of these composites requires specific know-how. It is not certain that the addition of this reinforcements will grant the desired functionalities, even more when it is used with very low incorporation percentage and of difficult dispersion. It will be a commitment between different criterions that will influence their processability, their mechanical behavior and their long a long term stability. This work has as main objective the characterization and the understanding of the behavior (mechanical, thermal, electric and to flame) of the reinforced TPE’s with micro and nanometrics particles.
European Commission under the sixth FP6 within the CEC-made-shoe project (ISTNMP 2004-507378)

碩士
大葉大學
食品工程研究所
88
The formulation and optimization of thermoplastic polyamide elastomers (TPAEs) physical properties were evaluated by mixture response surface methodology in this study. The molar ratio of main reaction was 1:1:10 (polyether polyol, chain extender and caprolactam). TPAEs prepared from different chain extenders blends of adipic acid (AA), terephthalic acid (TPA) and dimer acid (DA) were characterized by DSC, TGA, density measurement and water absorption measurement. The densities of the polymers increased as the content of TPA increased. The water absorption data showed the percent water absorption decreased as the contents of TPA increased. DSC and TGA thermograms showed that the initial thermal degradation temperatures of the polymers were affected insignificantly by changing the chain extender. The first derivative curve peak temperature of TGA showed that the thermal stability of the polymers increased as the contents of dimer acid increased.

碩士
大葉大學
食品工程研究所
87
The advantages of thermoplastic polyamide elastomers (TPAEs) are good physical and chemical properties, simpler processing, lower density, better control of product quality and recycling of scrap. The disadvantages are often requires long synthesis processing, high water absorbency, high monomer and oligomer content. The objects of this research is to modify the structure and process of TPAEs, so as to reduce the processing time, to decrease the monomer and oligomer content, and to enhance the TPAEs water resistance. The synthesis of C36 dimer acid modified TPAEs were done. In a one-step process, C36 dimer acid was mixed with adipic acid as a second chain extender in a reaction which included caprolacatam and PTMEG as hard segment and soft segment respectively. The thermal properties of TPAEs were studied by a DSC and TGA, and water absorption of TPAEs were tested to determined the tendency of samples to absorb moisture. Results showed that modified TPAEs with higher C36 dimer acid content have better thermal properties as well as water resistance. We also introduced Nylon 6 as starting materials of TPAEs polymerization . The synthesis of TPAEs was carried out by two-step process. First, Nylon 6 was depolymerized to oligomer, then reacted with PTMEG and added adipic acid as chain extender to form TPAEs. Results showed low degree of TPAEs polymerization and bed properties. It should need further investigation. Keywords: , ,, , one-step process, two-step process, , ,

碩士
大葉大學
食品工程研究所
87
Thermoplastic polyurethane elastomers (TPU) possess several excellent properties such as abrasion-resistance, elasticity, tear strength and oil-resistance. The synthesis of thermoplastic polyurethane was carried out by a one-shot process using polyester polyol, diphenyl-methane-4, 4-diisocyanate (MDI), and two chain extenders. 1,4-Butanediol and bisphenol A ethoxylate were used as the 1st and the 2nd chain extenders, respectively. From their viscosities and thermal properties data, we found that TPUs with a higher proportion of the 2nd chain extender show better thermal and molecular weight stabilities. Interestingly, the TPU with a higher proportion of the 2nd chain extender also shows more yellowish in color by comparing the appearance of TPUs after treated at a high temperature. DSC and TGA analysis also exhibited higher soften point and second degradation temperature of TPUs due to bisphenol A ethoxylate added.

Polyhedral oligomeric silsesquioxanes (POSS) are molecularly precise isotropic particles with average diameters of 1-2 nm. A typical T 8 POSS nanoparticle has an inorganic Si8O12 core surrounded by eight aliphatic or aromatic groups attached to the silicon vertices of the polyhedron promoting solubility in conventional solvents. Previously, efficient synthetic methods have been developed whereby one of the aliphatic groups on the periphery is substituted by a functional group capable of undergoing either homo- or copolymerization. In the current investigations, preparative methods for the chemical incorporation of POSS macromonomers in a series elastomers have been developed. Analysis of the copolymers using WAXD reveals that pendant POSS groups off the polymer backbones aggregate, and can crystallize as nanocrystals. From both line-broadening of the diffraction maxima, and also the oriented diffraction in a drawn material, the individual POSS sub-units are crystallizing as anisotropically shaped crystallites. The formation of POSS particle aggregation is strongly dependent on the nature of the polymeric matrix and the POSS peripheral group. X-ray studies show aggregation of POSS in ethylene-propylene elastomers occurred only with a phenyl periphery, whereas POSS particles with isobutyl and ethyl peripheries disperse within the polymer matrix. By altering the polymer matrix to one containing chain repulsive fluorine units, aggregation is observed with both the phenyl and isobutyl peripheries. Altering the polymer chain to poly(dimethylcyclooctadiene), POSS aggregates with isobutyl, ethyl, cyclopentyl, and phenyl peripheries. The formation of POSS nanocrystals increases the mechanical properties of these novel thermoplastic elastomers, including an increase in the tensile storage modulus and formation of a rubbery plateau region. Tensile tests of these elastomers show an increase in elastic modulus with increasing POSS loading. The elongation at break was as high as 720%. Cyclic tensile test show some hysteresis of the elastomers. However, the curves show Mullins effect behavior, commonly seen in elastomers. Elastomers with POSS dispersion, however, show poor mechanical properties. These results demonstrate the novel material property gains by the incorporation and aggregation of POSS in thermoplastic elastomers, as well as the influence of the POSS periphery.

碩士
崑山科技大學
材料工程研究所
100
This research is separately blend the styrene-butadiene rubber (SBR) and the butadiene rubber (BR) in the thermoplastic polyurethane (TPU), this dynamically vulcanized thermoplastic elastomer is abbreviation TPUSBR and TPUBR, and under different rubber contents and blending ratios, we research the vulcanization behavior, compatibility, post-thermal aging properties, mechanical properties and the foaming shape. From these results, we obtained the following results. During the mixing, the torque curves increases with increasing rubber contents, and in order to avoid deteriorating the rubber proportion cannot surpass 60%. The DMA spectra showed a single damping peak for the TPU/SBR blends, which suggests that TPU and SBR are miscible, in TPU/BR blends, it appears two characteristic peak, meaning that TPU/BR blends are partial immiscible. As for mechanical tests, the tensile strength and elongation ratio decrease with increasing rubber contents. On the other, that the resist abrasion and heat stability increases with increasing rubber contents. At the foaming test, both the TPU/SBR and TUR/BR all can succeed to foaming and to become foam materials.