Análise da influência das condições de mistura por extrusão sobre o comportamento de blendas poliméricas PBT/ABS

Abstract

At the present work several properties of PBT/ABS blends processed with different extrusion conditions as feed rate, screw speed and profile and die geometry were studied in order to verify how these parameters affect their properties. The specimens were obtained directly from the extruded blends to keep extrusion characteristics on the results. The main reason to add ABS to the PBT was to have tough PBT/ABS blends. It was verified that even without a compatibilizer, impact strength of the blends was higher than the impact strength of neat components. In addition, the ductile brittle temperature transition (DBTT) has decreased almost 60ºC when compared to the neat PBT. It was also verified that differences on processing parameters affect mostly DBTT, exhibiting values in the range of -5ºC to 40ºC. The best results were obtained using higher feed rates, low screw speed rotation, kneading blocks lagged 90º and shorter dies. It was also developed a degradation evaluation method and showed that the thermal mechanical degradation of the blend components can be verified by analyzing the consumption of the double bonds of the polybutadiene rich phase from ABS and the reduction of molecular weight of PBT. Although adequate results were obtained on preliminary degradation analyses of the components mixed in a torque rheometer, the method was insufficiently sensitive to identify significant differences on the degradation of blend components processed in a twin screw extruder.