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In this study calcium carbonate (CaCO3) particles are surface modified by using plasma polymerized natural gas and effects of surface modification of CaCO3 filler on mechanical properties of CaCO3-PP composites are investigated. Different combination of plasma factors / RF power, natural gas flow rate, and plasma discharge durations, are investigated. Mechanical properties such as tensile strength and Young&rsquo / s Modulus are measured by tensile testing machine. Storage modulus and loss modulus measurements are done by DMA. Some information about structures generated by natural gas plasma surface modification is obtained by FTIR tests. The tensile fracture surfaces of prepared composites are investigated by using SEM micrographs. It is concluded that, despite some enhancement obtained in the moduli / the technique of natural gas plasma surface modification of CaCO3 particles did not introduce significant improvement in mechanical properties of composite as expected. This result may partially be attributed to selected plasma parameters (i.e., flow rate, RF power, and discharge duration).

Methods of processing polypropylene (PP)/ liquid crystalline polymer blends to obtain high mechanical properties from injection molded samples were investigated in this dissertation. Three liquid crystalline polymers (LCPs), two liquid crystalline (LC) copolyesters and one LC poly(ester-amide), were used. The PP/LCP blends were compatibilized with a maleic anhydride grafted polypropylene (MAP) to enhance the mechanical properties. The effect of increasing MAP content on the mechanical properties, morphology, and interfacial tension of injection molded tensile bars and plaques made from blends with 30 wt% LCP was investigated. It was determined that MAP enhances both the tensile strength and modulus, but the tensile strength is increased to a greater degree than the tensile modulus. For the LC copolyesters, the tensile strength appeared to reach a maximum while for the LC poly(ester-amide) the tensile strength increased without limit in the range of MAP contents studied. Simultaneously, a finer dispersion was created as the MAP content was increased. Calculation of the interfacial tension from contact angle measurements indicated that the interfacial tension decreased as MAP was added to the PP matrix. Analysis of the MAP concentration after blending indicated that MAP did not react with the LCP, but enhanced tensile properties resulted from physical interaction such as hydrogen bonding. This mechanism is consistent with the greater property improvements found in the LC poly(ester-amide) blends where the amide group is expected to undergo stronger hydrogen bonding than the ester group. Analysis of the injection molding of these blends found that heat transfer and solidification significantly affected the flexural modulus of these blends. Injection molding conditions such as fill time, mold thickness, mold temperature and melt temperature were investigated in three molds of different thicknesses. Different processing relationships were found between the LC copolyesters and the LC poly(ester-amide). For the former LCP blends, the highest moduli were obtained from the thinnest mold in a manner parallel to that of the moduli of neat LCPs. For the latter LCP blends, the highest moduli were obtained in the intermediate thickness mold. The differences between the copolyester and LC poly(ester-amide)s processing / property relationships were related to the melt rheology of the LCPs. For the LC copolyesters, maximum mechanical properties were obtained when the melt temperature was selected so that the storage and loss moduli of the LCP were nearly equal. This equality of storage and loss moduli could not be achieved with the LC poly(ester-amide). In addition, upon cooling, the storage and loss moduli of the LC poly(ester-amide) indicated that rapid solidification occurred while a much lower rate of solidification was indicated for the LC copolyesters. In addition the mechanical properties were sensitive to the rate of cooling as indicated by the Graetz number. It was speculated that attainment of the highest mechanical properties was related to the LCP being deformed during the filling stage followed by rapid solidification of the LCP morphology upon cessation of flow. / Ph. D.

O uso de moldes-protótipo é uma opção para a obtenção de protótipos funcionais de peças de plástico injetadas. Estes protótipos devem possuir características mecânicas e físicas as mais próximas possíveis das peças finais obtidas em moldes de produção. A fim de diminuir o custo e o tempo de fabricação destes moldes, materiais alternativos, tais como o alumínio e ligas de zinco, podem ser empregados. Os diferentes níveis de condutividade térmica desses materiais resultam em diferentes taxas de resfriamento do polímero, o que pode influenciar nas propriedades mecânicas do moldado. O objetivo geral deste trabalho é entender a influência do material do molde-protótipo (zamac-8) e também da variação da temperatura do molde (TMolde) e da temperatura do fundido (TFund) nas propriedades mecânicas do moldado em Polipropileno (PP). Pretende-se então averiguar se existem parâmetros de temperatura que possam permitir a obtenção de protótipos funcionais com características próximas as de peças injetadas em molde de aço. O efeito do material zamac-8, da TMolde e da TFund sobre as propriedades do moldado foi avaliado através da comparação com um moldado injetado em um molde em aço. As técnicas de caracterização das amostras incluíram os ensaios de tração, impacto e calorimetria exploratória diferencial (DSC). Os resultados mostraram que o molde- protótipo em zamac-8 possui influência significativa somente para a energia de impacto. Com a variação da TMolde e da TFund foram obtidos moldados com diferentes propriedades no molde-protótipo em zamac-8, confirmando a influência da variação destes fatores sobre o moldado. Desta forma, foi possível criar um modelo de regressão onde através da otimização dessas temperaturas é possível predizer um resultado. Assim, para este estudo, foi possível diminuir a influência do uso do zamac-8 sobre o moldado, sendo que a regressão mostrou-se uma ferramenta importante na busca de protótipos funcionais com propriedades mecânicas mais próximas do produto final. / The use of prototype tooling is an option to obtain functional prototype of injection molded plastic parts. These prototypes should have mechanical and physical characteristics as close as possible to the final parts obtained in production molds. In order to reduce manufacturing cost and time of these molds, alternative materials, such as aluminum and zinc alloys, can be employed. The difference in thermal conductivity of these materials results in a variation of the cooling rates, which can influence the mechanical properties of the moldings. The main objective of this work is to understand the influence of the prototype tooling material (zamak-8) and also the variation of mold temperature (TMold) and the melt temperature (TMelt) on the mechanical properties of Polypropylene (PP). The idea is then to verify if these temperature parameters may allow obtaining functional prototypes with similar characteristics to the PP injected in a steel mold. The influence of the zamak-8 material and the TMold and TMelt on the properties of the molding was studied by comparison with the molding injected in a steel mold. The characterization techniques used were tensile and impact tests and differential scanning calorimetry (DSC). The results showed that the prototype tooling using zamak-8 has a significant influence only in the impact energy. By varying the TMold and TMelt, moldings injected in the prototype tooling with zamak-8 were obtained with different properties, confirming the influence of these parameters on the molding. In this way, a regression model was developed where, by optimizing these temperatures, it is possible to predict a result. Thus, in this study it was possible to reduce the influence of the zamak-8 on the molded, and regression was shown to be an important tool in the search for functional prototypes closer mechanical properties of the final product.

O uso de moldes-protótipo é uma opção para a obtenção de protótipos funcionais de peças de plástico injetadas. Estes protótipos devem possuir características mecânicas e físicas as mais próximas possíveis das peças finais obtidas em moldes de produção. A fim de diminuir o custo e o tempo de fabricação destes moldes, materiais alternativos, tais como o alumínio e ligas de zinco, podem ser empregados. Os diferentes níveis de condutividade térmica desses materiais resultam em diferentes taxas de resfriamento do polímero, o que pode influenciar nas propriedades mecânicas do moldado. O objetivo geral deste trabalho é entender a influência do material do molde-protótipo (zamac-8) e também da variação da temperatura do molde (TMolde) e da temperatura do fundido (TFund) nas propriedades mecânicas do moldado em Polipropileno (PP). Pretende-se então averiguar se existem parâmetros de temperatura que possam permitir a obtenção de protótipos funcionais com características próximas as de peças injetadas em molde de aço. O efeito do material zamac-8, da TMolde e da TFund sobre as propriedades do moldado foi avaliado através da comparação com um moldado injetado em um molde em aço. As técnicas de caracterização das amostras incluíram os ensaios de tração, impacto e calorimetria exploratória diferencial (DSC). Os resultados mostraram que o molde- protótipo em zamac-8 possui influência significativa somente para a energia de impacto. Com a variação da TMolde e da TFund foram obtidos moldados com diferentes propriedades no molde-protótipo em zamac-8, confirmando a influência da variação destes fatores sobre o moldado. Desta forma, foi possível criar um modelo de regressão onde através da otimização dessas temperaturas é possível predizer um resultado. Assim, para este estudo, foi possível diminuir a influência do uso do zamac-8 sobre o moldado, sendo que a regressão mostrou-se uma ferramenta importante na busca de protótipos funcionais com propriedades mecânicas mais próximas do produto final. / The use of prototype tooling is an option to obtain functional prototype of injection molded plastic parts. These prototypes should have mechanical and physical characteristics as close as possible to the final parts obtained in production molds. In order to reduce manufacturing cost and time of these molds, alternative materials, such as aluminum and zinc alloys, can be employed. The difference in thermal conductivity of these materials results in a variation of the cooling rates, which can influence the mechanical properties of the moldings. The main objective of this work is to understand the influence of the prototype tooling material (zamak-8) and also the variation of mold temperature (TMold) and the melt temperature (TMelt) on the mechanical properties of Polypropylene (PP). The idea is then to verify if these temperature parameters may allow obtaining functional prototypes with similar characteristics to the PP injected in a steel mold. The influence of the zamak-8 material and the TMold and TMelt on the properties of the molding was studied by comparison with the molding injected in a steel mold. The characterization techniques used were tensile and impact tests and differential scanning calorimetry (DSC). The results showed that the prototype tooling using zamak-8 has a significant influence only in the impact energy. By varying the TMold and TMelt, moldings injected in the prototype tooling with zamak-8 were obtained with different properties, confirming the influence of these parameters on the molding. In this way, a regression model was developed where, by optimizing these temperatures, it is possible to predict a result. Thus, in this study it was possible to reduce the influence of the zamak-8 on the molded, and regression was shown to be an important tool in the search for functional prototypes closer mechanical properties of the final product.