Made available in DSpace on 2014-06-12T23:14:37Z (GMT). No. of bitstreams: 2 arquivo8665_1.pdf: 2737608 bytes, checksum: 964c4063f82e235ed012a56e02f126ef (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O objetivo deste estudo foi avaliar a degradação por fratura sob tensão ambiental (environmental stress cracking ou ESC) de alguns polímeros vítreos, o poli(metacrilato de metila), o poliestireno e o poli (metacrilato de metila) tenacificado (PMMA-t), após esses polímeros terem sido submetidos a diferentes doses de radiação gama. A exposição à radiação gama foi realizada com doses de até 200kGy utilizando uma fonte de cobalto-60. Foram feitas avaliações prévias sobre o efeito da radiação gama na estrutura do polímero por meio de ensaios de massa molar, espectroscopia no infravermelho e visível, e ensaios de absorção de líquido, em que foram comparados os resultados obtidos para os polímeros irradiados nas diferentes doses com os do não-irradiado. Os estudos de ESC consistiram em submeter os polímeros a ensaios de tração em diferentes taxas de deformação e relaxação de tensão sob líquido e sem líquido. Análises de microscopia ótica e eletrônica de varredura foram feitas na superfície de fratura após ensaios de ESC. A radiação gama promoveu intensas mudanças na massa molar do PMMA e PMMA-t e ocasionou apenas modificações moderadas no PS. As velocidades de absorção de etanol pelo PMMA e PMMA-t aumentaram com o aumento da dose. Para o PS a velocidade de absorção de querosene reduziu nas duas doses maiores (100 e 200kGy). O PMMA e o PMMA-t mostraram nítida dependência do efeito de ESC com a dose de radiação gama e com as condições de ensaio, evidenciada pela maior redução percentual da tensão de ruptura e deformação na ruptura verificada em ensaios realizados com líquidos em comparação aos sem líquido. O poliestireno mostrou a menor dependência do efeito de ESC com a dose de radiação gama

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This research includes two topics. The first topic is prepared a series of poly(methyl methacrylate) (PMMA)-based copolymers through free radical copolymerizations of methyl methacrylate in the presence of the either 2 - vinyl - 4,6 -diamino - 1, 3, 5triazine(VDAT) or vinylbenzyl -thymine (VBT). Using 1H nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), we investigated the thermal properties and hydrogen-bonding interactions within blends of the two copolymers poly(2-vinyl-4,6-diamino-1,3,5-triazine-co-methyl methacrylate) (PVD AT-co-PMMA) and poly(vinylbenzylthymine-co-methyl methacrylate) (PVBT-co-PMMA). A large positive deviation in the behavior of the glass transition temperature determined by using the Kwei equation and DSC analyses indicated that strong multiple hydrogen-bonding interactions existed between the two copolymers. The FTIR and solid-state NMR spectroscopic analyses provided positive evidence for the presence of three hydrogen bonds between the diamino-1,3,5-triazine groups of PVDAT and thymine groups of PVBT. The second topic is synthesized a series of alkyne end-terminated poly(£^-Benzyl L-glutamate) (alkyne-PBLG), which was prepared by the ring-opening polymerization of the N-carboxyanhydride monomer of £^-Benzyl L-glutamate-carboxyanhydride. Then combination of the alkyne-PBLG with polyhedral oligomeric silsesquioxanes (POSS) with eight function groups are prepared through the click reation and formed a peptide-based block polymer with £\-helice and £]-sheet conformations. The thermal properties and structure of these polypeptides were characterized by using 1H NMR and FTIR. The FTIR, solid-state NMR and WXRD spectroscopic analyses provided evidence for the change of secondary structure between POSS and terminated peptide group, so that the conformation of £]-sheets and £\-helices would be influenced by the incorporation of POSS nanoparticle.

Abstract The company main S petrochemical industry as the research objects, about the company in the petrochemical industry in the production of poly methyl meth acrylate (PMMA) is commonly known as acrylic, is the case in the present and the future Direction of development and trends. Through theoretical analysis to understand the competitiveness of the petrochemical industry. In the new style, new technology, the steady growth in high-priced products, PMMA is also the tie in the application of this new product to increase the added value of industry and increase competitiveness. Current oil price fluctuations will also affect the price of PMMA, PMMA development and due process has matured, the industry is not the nature of product differentiation, so buyers can easily convert lower cost in the price comparison. Petrochemical industry¡¦s bargaining power in price relative to the low of the case, the opportunity to increase its own by external competitiveness will be the focus of the study. This research will force analysis and SWOT analysis of Six Strengths analysis in the current environment, the strategic approach should be taken, and expert interviews to further explore the effectiveness of the strategy changed. According to results of this study, S petrochemical industry planning to enhance the company does have the capacity PMMA and into the active material in the light guide panel supply chains to enhance the added value of PMMA. The results of this study will help to domestic petrochemical industry in the future formulation of policy can have a reference. . Key Words : PMMA, Competitiveness, Petrochemical

Nowadays, the components are made more and more small, the flow import or exports through the components are required frequently, so a set of micro-channel is need. The main aim of this paper is to study the effect of different inlet pressure and inlet flow velocity of micro-channel. By using the proposed numerical simulation, the pressure, velocity and equivalent stress inside the micro-channel corresponding to different inlet pressure and inlet velocity can be obtained. Also, the life of micro-channel was discussed also. Due to the size effect of the micro-channel, the boundary condition is set as . The error between the simulated and experiment results in less than 15%.

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Silica (inorganic)-g-polymer (organic) hybrid materials with a large variety of functionality have been studied intensively because of the improvement in their physical and chemical properties (e.g., thermal, mechanical, electrical, magnetic properties, etc.) with respect to conventional organic and inorganic materials. 1–3 This research work introduces a new strategy based on in situ formation of poly(methyl methacrylate) block copolymer grafted silica nanoparticles. The thesis is divided into two major parts. In the first part, the atom transfer radical polymerization (ATRP) method was used to synthesize poly(methyl methacrylate-b-trimethoxysilyl propyl methacrylate) (PMMA-b-PTMSPMA); and poly(methyl methacrylate-b-trimethoxysilyl propyl acrylate) (PMMA-b-PTMSPA) block copolymers. Gel permeation chromatography (GPC) was performed to determine the number-average molecular weight (Mn) and polydispersity index (Đ) of PMMA-b PTMSPMA and PMMA-b-PTMSPA. In addition, proton nuclear magnetic resonance spectroscopy (1H NMR) was used to confirm the successful synthesis of the above copolymers. In the second part, the copolymers were used to form silica nanoparticles grafted with poly(propyl methacrylate-b-methyl methacrylate) [silica-g-(PPMA-b PMMA)] and silica nanoparticles grafted with poly(propyl acrylate-b-methyl methacrylate) [silica-g-(PPA-b-PMMA)]. Fourier transform infrared spectroscopy (FT-IR) and 29Si solid-state NMR were performed to confirm the formation of silica-g-(PPMA-b PMMA) and silica-g-(PPA-b-PMMA). Additionally, thermogravimetric analysis (TGA) was performed to assess the thermal decomposition of silica-g-(PPMA-b-PMMA) and silica-g-(PPA-b-PMMA). Multiple microscopic techniques such as TEM, cryo-TEM, SEM, and AFM were used to study micellization of the silica-g-(PPMA-b-PMMA) and silica-g-(PPA-b-PMMA) in tetrahydrofuran (THF) and chloroform

As blendas poliméricas são importante alternativa ao mercado para se conseguir de forma economicamente vantajosa ou sob o ponto de vista de processabilidade produtos com propriedades otimizadas para aplicações específicas. Blendas com razões de composição variadas entre diferentes polímeros atendem aplicações muitas vezes com requisitos intermediários entre materiais. Este trabalho revisa sucintamente a literatura sobre blendas poliméricas, a produção em laboratório de uma blenda mecânica de poli(cloreto de vinila) PVC e poli(metacrilato de metila) - PMMA, avalia as propriedades de blendas com frações variadas de PVC/PMMA e discute o potencial de aplicação no mercado. A blenda miscível caracterizada tem custo, resistência à chama e propriedades mecânicas e térmicas intermediárias aos dois polímeros puros. / Polymer blends are an important alternative in the market for achieving, in an economically and advantageous way or just considering processability products with optimized properties for specific applications. Blends with variable composition ratios, between two different polymers, fit to applications with intermediate requirements between two different materials. This paper reviews slightly the literature about polymer blends, the lab scale production of a mechanical blend of poli(vinylene vhloride) - PVC and poly(methyl metacrylate) - PMMA with different PVC/PMMA ratios and the application potential. The miscible blend shows intermediate cost, flame resistance, mechanical and thermal properties then those shown by its neat polymers.

Chapas de poli(metacrilato de metila) podem ser modificadas por meio da adição de um agente promotor de ligações cruzadas e um plastificante objetivando incrementar seu desempenho durante a termoformagem. A interação intermolecular, modificada com a adição de diferentes quantidades de um agente promotor de ligações cruzadas (TEGDMA) e pela presença de um plastificante (DOP) faz com que as macromoléculas sejam ancoradas e afastadas respectivamente. O desenvolvimento deste trabalho objetivou, avaliar as propriedades físicas, mecânicas, térmicas e o processamento via termoformagem para duas diferentes temperaturas de termoformagem em um molde cilíndrico, a uma mesma taxa de deformação e determinado a influência da formulação, para cinco chapas que se diferenciaram nas quantidades de TEGDMA e uma quantidade fixada de DOP para duas das formulações. Os resultados mostraram que há incremento na deformação com as modificações introduzidas quando comparado a uma chapa sem adição de TEGDMA ou DOP e as propriedades destas chapas como dureza superficial, módulo de rigidez e temperatura de transição vítrea apresentaram mudanças sensíveis, que caracterizam vantagens no uso dos dois componentes. / Poly(methyl methacrylate) sheets can be modified adding a cross-linking agent and a plasticizer, to increase performance during thermoforming. The intermolecular interaction modification can be achieved adding different amount of cross-linking agent (TEGDMA) and a plasticizer (DOP). They have an effect on the network polymer system improving the intermolecular interaction and increasing the macromolecular distances, respectively. The aim of this study was to prepare acrylic sheets formulations with differents amounts of TEGDMA and a fixed amount of DOP, and thermoformed using at differents process temperatures and a mould cylinder at the same strain rate. Samples were carried out and their properties physical, mechanical, thermal and thermoformability was characterized. The results have shown strain increases, changes in surface hardness, Young moduli and glass transition temperature, compared to a reference acrylic sheet.

Electrospinning has been recognized as an efficient technique for the fabrication of polymer fibers. These electrospun fibers have many applications across a broad range of industries. In this research, optical transparent composites were successfully fabricated by embedding polyacrylonitrile (PAN) hollow nanofibers into poly (methyl methacrylate) (PMMA) matrix. The hollow PAN nanofibers were prepared by coaxial electrospinning. The PAN was used as the shell solution, and the mineral oil was used as the core solution. The resulting fibers were then etched with octane to remove the mineral oil from the core. The hollow PAN fibers were then homogeneously distributed in PMMA resins to fabricate the composite. The morphology, transmittance and mechanical properties of the PAN/PMMA composite were then characterized with an ESEM, TEM, tensile testing machine, UV-vis spectrometer and KD2 Pro Decagon device. The results indicated that the hollow nanofibers have relatively uniform size with one-dimensional texture at the walls. The embedded PAN hollow nanofibers significantly enhanced the tensile stress and the Young's modulus of the composite (increased by 58.3% and 50.4%, respectively), while having little influence on the light transmittance of the composite. The KD2 Pro device indicated that the thermal conductivity of the PMMA was marginally greater than the PAN/PMMA composite by 2%. This novel transparent composite could be used for transparent armor protection, window panes in vehicles and buildings, and airplane windshield etc.