A extrusão do polietileno linear de baixa densidade (LLDPE) é limitada por um defeito de processamento conhecido como fratura do fundido, que é um defeito de superfície no polímero extrudado. Esta torna-se áspera, resultando na perda do lustro e em uma mudança de determinadas propriedades de superfície. O objetivo deste trabalho foi obter um copolímero do politetrafluoroetileno reciclado com uma olefina que possa melhorar o processo de extrusão do LLDPE. O copolímero é obtido por meio da irradiação do PTFE reciclado sob atmosfera inerte para obter os radicais livres e, posteriormente, adicionado o monômero olefínico visando a sua enxertia na matriz polimérica (PTFE). Após um tempo de contacto, faz-se um tratamento térmico para a recombinação e eliminação dos radicais, ambos sob atmosfera reativa e/ou inerte. Foram utilizados três monômeros olefínicos, acetileno, etileno e 1,3-butadieno. O monômero 1,3-butadieno mostrou-se mais efetivo na enxertia. Os resultados foram caracterizados pela espectroscopia de absorção na região do infravermelho com transformadas de Fourier (FTIR), análise termogravimétrica (TGA) e termogravimetria derivada (DTG). O copolímero obtido foi misturado nas concentrações de 0,2 a 2,0 % em massa com o LLDPE. As propriedades reológicas desta mistura foram determinadas com um reômetro de torque. Os resultados demonstram que o processo utilizado fornece um copolímero que, usado como aditivo ao LLDPE, melhora o processo de extrusão eliminando o defeito de processamento conhecido como fratura do fundido. / The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as ‘melt fracture’ or ‘sharkskin’, which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect ‘melt fracture’.

A extrusão do polietileno linear de baixa densidade (LLDPE) é limitada por um defeito de processamento conhecido como fratura do fundido, que é um defeito de superfície no polímero extrudado. Esta torna-se áspera, resultando na perda do lustro e em uma mudança de determinadas propriedades de superfície. O objetivo deste trabalho foi obter um copolímero do politetrafluoroetileno reciclado com uma olefina que possa melhorar o processo de extrusão do LLDPE. O copolímero é obtido por meio da irradiação do PTFE reciclado sob atmosfera inerte para obter os radicais livres e, posteriormente, adicionado o monômero olefínico visando a sua enxertia na matriz polimérica (PTFE). Após um tempo de contacto, faz-se um tratamento térmico para a recombinação e eliminação dos radicais, ambos sob atmosfera reativa e/ou inerte. Foram utilizados três monômeros olefínicos, acetileno, etileno e 1,3-butadieno. O monômero 1,3-butadieno mostrou-se mais efetivo na enxertia. Os resultados foram caracterizados pela espectroscopia de absorção na região do infravermelho com transformadas de Fourier (FTIR), análise termogravimétrica (TGA) e termogravimetria derivada (DTG). O copolímero obtido foi misturado nas concentrações de 0,2 a 2,0 % em massa com o LLDPE. As propriedades reológicas desta mistura foram determinadas com um reômetro de torque. Os resultados demonstram que o processo utilizado fornece um copolímero que, usado como aditivo ao LLDPE, melhora o processo de extrusão eliminando o defeito de processamento conhecido como fratura do fundido. / The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as ‘melt fracture’ or ‘sharkskin’, which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect ‘melt fracture’.

Erlangen, Nürnberg, Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Linear Low Density Polyethylene (LLDPE) is a relatively new plastic that is becoming widely used in many applications. In fact the production rate of LLDPE is vital in determining the process characteristics and subsequent properties of the end products. In this work we have examined, specifically, the influence of surfaces and structure on the rheology and processing properties of LLDPE. A review of the effect of surfaces on the rheology and processing of polymers is given, with particular emphasis on the interaction between metals and polymers. The influence of oxidative degradation and radiation on the structural modification of polymers is also reviewed. Standard rheological characterisation tests determined there was no effect of various metal and teflon surfaces on the rheology of LLDPE. There was also no evidence of wall slip on metal or teflon surfaces. The generalised Maxwell model (with Wagner's damping function) predicted dynamic and steady shear properties at standard characterisation rates well. The effects of degradation of LLDPE were quantified, and an increase in elasticity due to increased crosslinking of long polymer chains was noted during degradation tests. This effect increased with time (after a degradation time) and temperature. There was no effect of metals on the degradation properties of LLDPE, however, there was evidence of increased carbon-oxygen species (or increased oxidation) at the metal/LLDPE interface for metals containing copper at the interface (copper and brass). The migration of copper was facilitated by the low heat of formation of the oxides on the copper-containing metals. Increasing gamma and ion beam radiation dose decreased melting temperatures, heats of melting and crystallinity due to increased crosslinking at the crystallite surfaces and the reduction in crystal sizes. Gel fraction and tightness of gel increased with radiation dose due to increased crosslinking. Increased radiation dose also increased the elasticity and flow resistance of the samples as shown by rheological tests. The extension of a power law representation of the relaxation modulus of irradiated samples was extended to predict stress build-up and relaxation properties in steady shear tests. There was little effect of type of radiation (gamma or ion beam) on physical and rheological properties. However, there was a marked increase in the effects of irradiation in the melt (150degC) on the physical and rheological properties of LLDPE, which was due to the increased effective amorphous nature of the sample in the melt. The equivalence of the effects of degradation and irradiation are discussed. Viscosity was well predicted by the generalised Maxwell model (with Wagner's damping function) at processing rates. The normal stress differences calculated by Boger and Denn's model correlated well with this generalised Maxwell model, which was due to the inclusion of a flow rearrangement term. There was a marked increase in exit pressures, exit losses, flow rearrangement length, flow singularity, and exit stresses for flow over brass inserts at the die exit. These effects coincided with the production of a porous, copper-rich brass surface and it was postulated that this was the results of surface dezincification which caused increased adhesion between the LLDPE and the brass via physical interlocking at the porous surface. Extension of these results to melt fracture are discussed.

Flexible packaging is a growing successful market and the majority of flexible package applications are for the food industry. The demand for process optimization and reduced production costs, has led to an increase in flexible packaging. However, fast production lines can result in contamination in the seal area. For flexible food packaging, contamination is considered any food particle or substance trapped in the seal area. Current quality control processes can detect contamination in the seal area, but it is not determined if seal contamination effects seal quality. Oil-based and sodium based snack foods are two common categories that can be packaged on a horizontal flow film and seal (HFFS) flow-wrap machine. The study uses vegetable oil and a salt water solution to simulate the effect of liquid contamination along the T-point of flexible pouches made on an HFFS. The T-point refers to where the fin seal meets the end seal and requires the seal jaw to seal through four layers of film, which is the most difficult point to seal. The study tests a combination of different sealing temperatures and dwell time to determine the optimal sealing condition for a hermetic seal. A quality hermetic seal provides an enclosed seal with no leaks due to successful polymer chain entanglement between the two sealant layers. The different test categories of the study are non-contaminated (control), salt water solution for salt based foods, and vegetable oil for oil-based foods. Given the test parameters of the study, 140⁰C sealing temperature and 0.3 seconds dwell time are considered to be the optimal sealing condition for all three test categories. For Phase 1 of the study, salt water has a lower hermeticity pass rate compared to vegetable oil and non-contaminated seals. In addition, the effect of refrigerated storage temperature and ambient storage temperature did not show to be significant for any of the test categories. However, refrigerated conditions showed a higher hermeticity pass rate, but it was not statistically different. The findings for seal strength indicated no test category had higher or lower seal strength over the 14 day test period. Overall, the study shows there is no effect of liquid contaminant on hermeticity and seal strength for flexible film with LLDPE sealant layer.

<P> Responsive polymer composites were developed by incorporating a functional component into a nonpolar amorphous polymer. The response of the polymer composite is the change in color observed upon exposing the composite to different acids. One application could be a device to monitor the diffusion of different acids in different polymers. </p> <p> The research contained within this thesis deals with an investigation of basic properties of polymer composites. This was accomplished, first through the preparation of a composite of phenolphthalein disodium and Linear Low Density Polyethylene (LLDPE), second, by monitoring the decolorizing process and the aspects that affect it. The investigations included the extrusion parameters, types of acid, acid concentration and indicator concentration, and lastly by quantifying the process through the comparison of empricial diffusion coefficients and corresponding diffusion rates. </p> <p> This study has shown that decolorization occurs at a fast pace in the presence of acetic acid and slow in the presence of hydrochloric acid. Further as the indicator concentration increases, the decolorization process becomes slower. Techniques used to monitor the properties were Scanning Electron Microscopy (SEM) micrographs of freeze fractured composites, Differential Scanning Calorimetry (DSC) scans for the starting materials as well as the composites, and photography of the cross-sections of sample composite cylinders. </p> / Thesis / Master of Science (MSc)

O uso do método de esterilização por radiação gama ajuda na redução da contaminação microbiológica. O polietileno linear de baixa densidade (PELBD) é um polímero de cadeias lineares e ramificações curtas. Neste trabalho o PELBD injetado foi irradiado por uma fonte de 60Co com 2000 kCi de atividade, na presença de ar, em doses de 5, 10, 20, 50 ou 100 kGy e taxas de dose de cerca de 5 kGy.h-1 em temperatura ambiente (25 ºC). Após a irradiação, foi necessário submeter as amostras a um tratamento térmico em uma estufa por 60 min a 100 ºC para a recombinação e aniquilação dos radicais residuais. Na sequência as amostras injetadas foram irradiadas e caracterizadas para identificar os efeitos de degradação térmica, cisão e reticulação em cada dose. Verificou-se uma degradação térmica da resina ao passar pelo processo de modelagem por injeção confirmada pela análise de FTIR. Os PELBD injetados irradiados nas doses de 5, 10 ou 20 kGy tiveram maior tendência a cisão do que aqueles nas doses de 50 ou 100 kGy, nos quais predominou a reticulação. Desta forma determinaram-se os efeitos da irradiação e do processo nos PELBD moldados por injeção. / The use of the method of sterilization by gamma radiation helps in reducing microbiological contamination. The linear low density polyethylene (LLDPE) is a linear polymer chain with short chain branching. In this work, the LLDPE were irradiated in 60Co gamma source with 2000 kCi of activity, in presence of air, with doses of 5, 10, 20, 50 or 100 kGy, at about 5 kGy.h-1 dose rate, at room temperature. After irradiation, the samples were heated for 60 min at 100 ºC to promote recombination and annihilation of residual radicals. In the sequence LLDPE injected samples were irradiated and characterized to identity the effects of terminal degradation, scission end crosslinking occurred in each dose. There was a thermal degradation of the resin through the process of injection molding confirmed by FTIR analysis. And LLDPE injected irradiated at doses of 5, 10 or 20 kGy has a greater tendency to scission than those at doses of 50 or 100 kGy, where predominated crosslinking consequently the effects of irradiation and injection molding were investigated in LLDPE processed.

O uso do método de esterilização por radiação gama ajuda na redução da contaminação microbiológica. O polietileno linear de baixa densidade (PELBD) é um polímero de cadeias lineares e ramificações curtas. Neste trabalho o PELBD injetado foi irradiado por uma fonte de 60Co com 2000 kCi de atividade, na presença de ar, em doses de 5, 10, 20, 50 ou 100 kGy e taxas de dose de cerca de 5 kGy.h-1 em temperatura ambiente (25 ºC). Após a irradiação, foi necessário submeter as amostras a um tratamento térmico em uma estufa por 60 min a 100 ºC para a recombinação e aniquilação dos radicais residuais. Na sequência as amostras injetadas foram irradiadas e caracterizadas para identificar os efeitos de degradação térmica, cisão e reticulação em cada dose. Verificou-se uma degradação térmica da resina ao passar pelo processo de modelagem por injeção confirmada pela análise de FTIR. Os PELBD injetados irradiados nas doses de 5, 10 ou 20 kGy tiveram maior tendência a cisão do que aqueles nas doses de 50 ou 100 kGy, nos quais predominou a reticulação. Desta forma determinaram-se os efeitos da irradiação e do processo nos PELBD moldados por injeção. / The use of the method of sterilization by gamma radiation helps in reducing microbiological contamination. The linear low density polyethylene (LLDPE) is a linear polymer chain with short chain branching. In this work, the LLDPE were irradiated in 60Co gamma source with 2000 kCi of activity, in presence of air, with doses of 5, 10, 20, 50 or 100 kGy, at about 5 kGy.h-1 dose rate, at room temperature. After irradiation, the samples were heated for 60 min at 100 ºC to promote recombination and annihilation of residual radicals. In the sequence LLDPE injected samples were irradiated and characterized to identity the effects of terminal degradation, scission end crosslinking occurred in each dose. There was a thermal degradation of the resin through the process of injection molding confirmed by FTIR analysis. And LLDPE injected irradiated at doses of 5, 10 or 20 kGy has a greater tendency to scission than those at doses of 50 or 100 kGy, where predominated crosslinking consequently the effects of irradiation and injection molding were investigated in LLDPE processed.

The sterically expanded octamethyloctahydrodibenzofluorene moiety, C29H38 (Oct), has been incorporated into ansa-metallocenes and constrained geometry catalysts (CGC's). Utilization of this sterically expanded version of fluorene has resulted in solidstate anomalies for both systems. The ansa-metallocenes Me2C(n5-C5H4) (n5-C29H36)MCl2, M = Zr, Hf and Me2C(n5-C5H4)(n5-C29H36)ZrBn2 demonstrate crystal motifs expected for ansametallocenes while Me2C(n5-C5H4)(n5-C29H36)MMe2, M=Zr, Hf exhibit diffuse diffraction, a phenomenon that is extremely unusual for organometallic complexes. This crystalline anomaly is the result of a disorder restricted to two dimensions caused by the rare pillared motif of the system. The best solution for this system consists of parallel and anti-parallel pillars present in a 60:40 ratio. The solid state anomaly observed for the Oct-CGC's occurs on a molecular level. The parent Oct-CGC, Me2Si(1-C29H36)(1-N-tBu)ZrCl2·OEt2, demonstrates an unprecedented n1 ligation to the fluorenyl-based ring. Systematic derivatization of this system via halide substitution, alkylation, and exchange of Zr for Hf has revealed that the n1 ligation persists for systems with small substituents on the metal center capable of retaining a coordinated ether. It is hypothesized that the unusual structure of this new Oct-CGC results in Me2Si(1-C29H36)(1-N-tBu)ZrCl2·OEt2/MAO (MAO = methylaluminoxane) being six times more active in the homopolymerization of 1-octene than ethylene. When compared to the prototypical Ti-CGC Me2Si(n5-C5Me4)(n1-N-tBu)TiCl2/MAO, the Oct-CGC is 85 times more reactive in the homopolymerization of 1-octene and 52 times more active in the copolymerization of 1-octene and 4-methyl-1-pentene. The high reactivity of the Oct-CGC towards alpha-olefins results in the observation of an unyielding comonomer effect in the copolymerization of these olefins with ethylene. In addition, the Oct-CGC is perhaps the most syndioselective catalyst known. With an enantiofacial selectivity of 99.7% and a remarkably high activity towards alpha-olefins, the Oct-CGC is capable of producing the highest melting syndiotactic polypropylene (Tm = 165oC, annealed = 174oC) reported thus far. The high activity and syndioselectivity of the Oct-CGC can be extended to the production of syndiotactic poly(4-methyl-1-pentene) with the highest melting point thus far reported (Tm = 215oC).

Neste trabalho, inicialmente, foram obtidos TPSs (amidos termoplásticos) com diferentes concentrações de amido e plastificantes, por processamento em câmara de mistura, com o objetivo de determinar formulações para estudo em extrusora reativa. As formulações de TPS que apresentaram os melhores resultados de torque reométrico foram as que continham 39%m/m de amido. Investigou-se a influência da velocidade da rosca na obtenção de TPS por extrusora reativa, e os resultados mostraram que este parâmetro teve pequena influência na estabilidade do amido termoplástico, sendo possível utilizar 150 rpm de rotação. Foram produzidas 5 blendas com razões de TPS:PEBDL variando de 30:70; 40:60; 50;50; 60:40 e 70:30 para o desenvolvimento de um sistema ligante para a injeção de alumina pelo processo de moldagem de pós (MPI), a partir das quais foi possível analisar a influência do TPS no PEBDL, através de análises de MEV, IF, TGA, DMA e propriedades mecânicas. Quanto maior a concentração de TPS nas blendas, mais heterogênea foi a morfologia observada por MEV e menor o módulo de armazenamento e de perda obtidos por DMA. Este comportamento foi similar ao encontrado pela análise de resistência à tração, que apresentou propriedades mecânicas pobres para elevadas concentrações de TPS. Foram escolhidas três blendas para testar como veículo orgânico em feedstocks de alumina, com carga de partícula sólida de 45%, 50% e 55%v/v de Al2O3. A carga crítica para o sistema ligante-partículas sólidas determinada por reometria de torque foi de 50%v/v de alumina. / In this work, TPSs (thermoplastic starch), with different concentrations of starch and plasticizers for processing in the mixing chamber, were obtained in order to determine formulations for study in a reactive extruder. The TPS formulations that showed the best results for the rheometric torque were those containing 39% w/w starch. The influence of the screw speed to obtain TPS in the reactive extruder was investigated and the results showed that this parameter had little influence on the stability of the thermoplastic starch, allowing the use of 150 rpm rotation speed. Five blends were produced, with TPS:LLDPE ratios of 30:70; 40:60; 50:50; 60:40 and 70:30, to develop a binder for alumina injection by the powder molding process (MPI). From these five systems it was possible to analyze the influence of TPS in LLDPE through SEM analyzes, MFI, TGA, DMA and mechanical properties. The higher the concentration of TPS in blends, more heterogeneous morphology was observed by SEM and the lowest storage and loss modulus were obtained by DMA. This behavior was similar to that found by analysis of tensile strength, which showed poor mechanical properties for high concentrations of TPS. Three blends were chosen for testing as an organic vehicle in alumina feedstocks, with solid particles load of 45%, 50% and 55% v/v of Al2O3. The critical load for the system binder-solid particles, determined by torque rheometry, was 50% v/v of alumina.