Orientador: Maria do Carmo Gonçalves / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-05T15:56:25Z (GMT). No. of bitstreams: 1 Segatelli_MarianaGava_M.pdf: 3623345 bytes, checksum: 223789f87f6234b864c485f4c771efa2 (MD5) Previous issue date: 2005 / Resumo: O objetivo principal deste trabalho foi avaliar a incorporação de fibras curtas de sílica (FS) e da borracha etileno-propileno-dieno funcionalizada com anidrido maleico (EPDM-g-AM) em polimérica de poliamida 6 (PA 6). A fibra utilizada como carga é um produto natural constituído de sílica amorfa proveniente da fossilização de animais multicelulares. Com a finalidade de promover a melhor adesão interfacial entre a fibra e a matriz polimérica, as fibras foram modificadas com aminopropiltrietoxissilano (APTS), um agente de acoplamento. Os materiais foram preparados em extrusoras monorosca e duplarosca e, submetidos a ensaios mecânicos de tração, flexão e de impacto Izod. Foram também avaliadas as características térmicas e morfológicas desses materiais. As fibras de sílica não alteraram a estabilidade térmica da PA 6 e apresentaram eficiência de reforço, dentro do intervalo de composição estudado; entretanto, o alongamento na ruptura foi comprometido. A resistência ao impacto do polímero não variou significativamente com a incorporação de FS. Por outro lado, o tipo de extrusora utilizada para processamento alterou a cristalinidade da PA 6 e, conseqüentemente, as propriedades mecânicas nos compósitos binários de PA 6/FS. A modificação da superfície da fibra com APTS não foi adequada para melhorar as propriedades mecânicas, no entanto, a análise da microestrutura dos compósitos obtidos indicou adesão entre as fases. Em relação às blendas de PA 6/EPDM-g-AM, o tamanho médio de partícula da fase dispersa promoveu um efeito de tenacificação da PA 6. Os compósitos ternários de PA 6 contendo 20% de EPDM-g-AM e proporções diferentes de FS (5 a 20%) apresentaram redução na resistência ao impacto quando pequenas quantidades de FS foram adicionadas. Apesar da redução no valor desta propriedade, os compósitos obtidos exibiram boa tenacidade. Desta forma, a combinação de fibras curtas de sílica e borracha de EPDM-g-AM em poliamida 6 permitiu recuperar parcialmente a rigidez e a resistência ao impacto, que são comprometidas quando esses aditivos são utilizados separadamente. / Abstract: The main goal of this work was to evaluate the incorporation of short silica fibers (SF) and ethylene-propylene-diene rubber, functionalized with maleic anhydride (EPDM-g-MA), in a polyamide 6 (PA 6) matrix. The fiber used as filler is a natural product made up of amorphous silica from the fossilization of multicelular animals. In order to promote a better interfacial adhesion between the fiber and the polymeric matrix, fibers were modified with the aminopropyltriethoxysilane (APTS) coupling agent. The materials were prepared in single and twin-screw extruders for tensile, flexural and Izod impact mechanical tests. The mechanical, morphological and thermal properties of these materials were evaluated. Silica fibers did not change the thermal stability of the polymer and presented efficiency for reinforcement. However, the elongation at break was impaired. The impact strength of the polymer did not change significantly with the SF content. On the other hand, the type of extruder used for processing changed the mechanical properties and the crystallinity of PA 6 in the PA 6/SF binary composites. The fiber surface modification with APTS was not effective, as verified by the decrease of the mechanical properties. The morphology of composites showed adhesion between the phases. Taking into account the PA 6/EPDM-g-MA blends, the average size of dispersed phase, associated to impact strength in the 20% EPDM-g-MA composition promoted a toughening effect of the blends. Ternary PA 6 composites containing 20% EPDM-g-MA and different SF amounts (5-20%) presented tendency towards the reduction of the impact strength when small SF amounts were added. In spite of the reduction in the value of this mechanical property, the composites obtained exhibited good toughness. Thus, combining short silica fibers and EPDM-g-MA rubber with polyamide 6, the stiffness and the impact strength, that are impaired when these additives are separately used, were partially recovered. / Mestrado / Físico-Química / Mestre em Química

A adição de fibras de sílica em compósitos de polipropileno (PP) foi investigada neste trabalho como uma proposta de desenvolvimento de novos materiais utilizados pela indústria automotiva, os quais permitam a redução de peso do veículo e a consequente economia de combustível. As fibras são leves, constituídas de sílica amorfa e tratadas com aminossilano para uma melhor interação com a matriz polimérica. Compósitos de PP homopolímero, bem como de compósitos de PP heterofásico modificados com o copolímero etileno e 1-octeno (POE), foram formulados utilizando-se 20% de fibras de sílica e com PP funcionalizado com anidrido maleico (PP-g-MAH) como compatibilizante. As amostras foram avaliadas quanto às propriedades mecânicas, térmicas, características morfológicas, anisotropia e quanto a requisitos específicos, como emissões de voláteis, odor e resistência a riscos. O compósito de PP homopolímero na presença de 2% de PP-g- MAH apresentou o melhor balanço de propriedades, porém com comprometimento quanto à tenacidade. A análise morfológica desta formulação indicou a presença de fibras descoladas, demonstrando que o tratamento das fibras com o aminossilano, não foi totalmente efetivo para a redução das tensões interfaciais. Os compósitos de PP heterofásico modificados com POE (5% em peso) e com fibras de sílica apresentaram boa dispersão, forma e tamanho de domínios elastoméricos, os quais promoveram um bom efeito de tenacificação. O copolímero POE atuou como um agente compatibilizante, melhorando a adesão fibra-polímero. Por outro lado, estes compósitos apresentaram um grande número de partículas de borracha descoladas da matriz por cavitação, sugerindo que a adesão entre as fases pode ser melhorada, apesar da afinidade química da blenda PP/POE. De uma forma geral, as fibras curtas de sílica constituem uma alternativa potencial para o reforço de compósitos de PP. Além de menor densidade, os compósitos estudados apresentaram bons resultados quando comparados a formulações com o emprego de talco, o qual é muito empregado em peças automotivas. / The addition of silica fibers in polypropylene (PP) composites was investigated on this work as a proposal to develop new materials used in automotive industry, in order to enable the reduction of vehicle weight and the resulting fuel economy. The fibers are lightweight, made of amorphous silica and treated with amine silane for better interaction with the polymer matrix. Composites of PP homopolymer and PP heterophasic composites modified with ethylene and 1-octene (POE) were formulated using 20% of silica fibers as reinforcement and PP functionalized with maleic anhydride (PP-g-MAH) as compatibilizer agent. The samples were evaluated for mechanical, thermal, morphological, anisotropy, as well as specific requirements such as emissions of volatiles, odor and scratch resistant. The composite of PP homopolymer in the presence of 2% of PP-g-MAH showed the best balance of properties, however the tenacity was impaired. The morphological analysis of this formulation indicated the presence of detached fibers, demonstrating that treatment of fibers with the amine silane was not totally effective in reducing the interfacial tensions. Heterophasic PP composites modified with POE (5 wt%) and silica fibers presented good dispersion, shape and size of elastomeric domains, promoting a good toughening effect. The POE copolymer acted as a coupling agent, enhancing the adhesion fiber-polymer. On the other hand, these composites showed a large number of rubber particles detached from the matrix by cavitation, suggesting that the adhesion between the phases can be improved, despite the chemical affinity of the blend PP/POE. In general, short silica fibers are a potential alternative for polypropylene composites reinforcement. In addition to lower density, the studied composites demonstrated good results when compared to formulations with the use of talc, which is very used in automotive parts.

A adição de fibras de sílica em compósitos de polipropileno (PP) foi investigada neste trabalho como uma proposta de desenvolvimento de novos materiais utilizados pela indústria automotiva, os quais permitam a redução de peso do veículo e a consequente economia de combustível. As fibras são leves, constituídas de sílica amorfa e tratadas com aminossilano para uma melhor interação com a matriz polimérica. Compósitos de PP homopolímero, bem como de compósitos de PP heterofásico modificados com o copolímero etileno e 1-octeno (POE), foram formulados utilizando-se 20% de fibras de sílica e com PP funcionalizado com anidrido maleico (PP-g-MAH) como compatibilizante. As amostras foram avaliadas quanto às propriedades mecânicas, térmicas, características morfológicas, anisotropia e quanto a requisitos específicos, como emissões de voláteis, odor e resistência a riscos. O compósito de PP homopolímero na presença de 2% de PP-g- MAH apresentou o melhor balanço de propriedades, porém com comprometimento quanto à tenacidade. A análise morfológica desta formulação indicou a presença de fibras descoladas, demonstrando que o tratamento das fibras com o aminossilano, não foi totalmente efetivo para a redução das tensões interfaciais. Os compósitos de PP heterofásico modificados com POE (5% em peso) e com fibras de sílica apresentaram boa dispersão, forma e tamanho de domínios elastoméricos, os quais promoveram um bom efeito de tenacificação. O copolímero POE atuou como um agente compatibilizante, melhorando a adesão fibra-polímero. Por outro lado, estes compósitos apresentaram um grande número de partículas de borracha descoladas da matriz por cavitação, sugerindo que a adesão entre as fases pode ser melhorada, apesar da afinidade química da blenda PP/POE. De uma forma geral, as fibras curtas de sílica constituem uma alternativa potencial para o reforço de compósitos de PP. Além de menor densidade, os compósitos estudados apresentaram bons resultados quando comparados a formulações com o emprego de talco, o qual é muito empregado em peças automotivas. / The addition of silica fibers in polypropylene (PP) composites was investigated on this work as a proposal to develop new materials used in automotive industry, in order to enable the reduction of vehicle weight and the resulting fuel economy. The fibers are lightweight, made of amorphous silica and treated with amine silane for better interaction with the polymer matrix. Composites of PP homopolymer and PP heterophasic composites modified with ethylene and 1-octene (POE) were formulated using 20% of silica fibers as reinforcement and PP functionalized with maleic anhydride (PP-g-MAH) as compatibilizer agent. The samples were evaluated for mechanical, thermal, morphological, anisotropy, as well as specific requirements such as emissions of volatiles, odor and scratch resistant. The composite of PP homopolymer in the presence of 2% of PP-g-MAH showed the best balance of properties, however the tenacity was impaired. The morphological analysis of this formulation indicated the presence of detached fibers, demonstrating that treatment of fibers with the amine silane was not totally effective in reducing the interfacial tensions. Heterophasic PP composites modified with POE (5 wt%) and silica fibers presented good dispersion, shape and size of elastomeric domains, promoting a good toughening effect. The POE copolymer acted as a coupling agent, enhancing the adhesion fiber-polymer. On the other hand, these composites showed a large number of rubber particles detached from the matrix by cavitation, suggesting that the adhesion between the phases can be improved, despite the chemical affinity of the blend PP/POE. In general, short silica fibers are a potential alternative for polypropylene composites reinforcement. In addition to lower density, the studied composites demonstrated good results when compared to formulations with the use of talc, which is very used in automotive parts.

A porous silica –silica composite was processed with varying fiber diameters using the slurry moulding technique. The advantage of the process was that the density of the composite could be processed to the required levels. The reinforcements used were fibers obtained by leaching E-glass cloth, imported silica fibers with diameter <1.8µ and hollow silica fibers processed using sol-gel method. All the properties depend on the density of the composite. The compressive strength was measured in the perpendicular and parallel directions. Strength was high when the load axis was along the fiber direction. The composite with fine fibers (< 1.8 µ pure silica fibers) showed higher strength compared to the leached silica fibers. The thermal conductivity measurement on these composites showed an increase with temperature owing to the domination of radiation at high temperatures. As the vacuum level was approached, the thermal conductivity showed a decrease due to the absence of the convective part of the thermal transfer process. For use as a thermal protection system, it is important to measure the thermal response of these tiles in a simulated re-entry environment. Tests were done to measure this response for a given heat flux conditions at 38W/cm2 to 75W/cm2 and the backwall temperature was measured for various types of silica -silica composites. The role of impurities like sodium and B2O3 was also studied with respect to the conversion from amorphous to crystalline forms of SiO2. The severe increase in the coefficient of thermal expansion when SiO2 converted from amorphous to α– crystoballite was also measured. CSZP CSZP which belongs to the NZP family was processed using the co-precipitation technique. The influence of substituting the ‘P’ site with ‘Si’ atom was studied for its influence on thermal expansion – both at the bulk level by dilatometry and at the intrinsic level using high temperature XRD. For many anisotropic materials micro-cracking is a serious issue while cooling from the sintering temperature. It has been previously proved that this extent of micro-cracking depends on the particle size. Smaller the particle size is therefore preferred. One of the significant results obtained in this study was the successful use of microwaves to process crack free CSZP with fine grain size. CSZP with 95% density having a grain size as small as 1µ have been processed using microwave sintering. Dielectric property evaluation namely dielectric constant, dielectric loss and temperature coefficient of resonant frequency which are vital parameters required if this material is to be used as a candidate TPS have also been measured. The thermal conductivity of the sample was measured using Laser flash apparatus and was found to be 0.9 W/mk which provides an indication that this material can be used as a successful material for TPS. Finally a composite consisting of silica fiber with CSZP as matrix was processed and tested for heat flux. The low back wall temperature indicates that this material is a potential replacement for silica tile.

abstract: Ordered mesoporous materials have tunable pore sizes between 2 and 50 nm and are characterized by ordered pore structures and high surface areas (~1000 m2/g). This makes them particularly favorable for a number of membrane applications such as protein separation, polymer extrusion, nanowire fabrication and membrane reactors. These membranes can be fabricated as top-layers on macroporous supports or as embedded membranes in a dense matrix. The first part of the work deals with the hydrothermal synthesis and water-vapor/oxygen separation properties of supported MCM-48 and a new Al-MCM-48 type membrane for potential use in air conditioning systems. Knudsen-type permeation is observed in these membranes. The combined effect of capillary condensation and the aluminosilicate matrix resulted in the highest separation factor (142) in Al-MCM-48 membranes, with a water vapor permeance of 6×10-8mol/m2&#61655;Pa&#61655;s. The second part focuses on synthesis of embedded mesoporous silica membranes with helically ordered pores by a novel Counter Diffusion Self-Assembly (CDSA) method. This method is an extension of the interfacial synthesis method for fiber synthesis using tetrabutylorthosilicate (TBOS) and cetyltrimethylammonium bromide (CTAB) as the silica source and surfactant respectively. The initial part of this study determined the effect of TBOS height and humidity on fiber formation. From this study, the range of TBOS heights for best microscopic and macroscopic ordering were established. Next, the CDSA method was used to successfully synthesize membranes, which were characterized to have good support plugging and an ordered pore structure. Factors that influence membrane synthesis and plug microstructure were determined. SEM studies revealed the presence of gaps between the plugs and support pores, which occur due to shrinking of the plug on drying. Development of a novel liquid deposition method to seal these defects constituted the last part of this work. Post sealing, excess silica was removed by etching with hydrofluoric acid. Membrane quality was evaluated at each step using SEM and gas permeation measurements. After surfactant removal by liquid extraction, the membranes exhibited an O2 permeance of 1.65x10-6mol/m2.Pa.s and He/O2 selectivity of 3.30. The successful synthesis of this membrane is an exciting new development in the area of ordered mesoporous membrane technology. / Dissertation/Thesis / Ph.D. Chemical Engineering 2011

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