Transport of water through polyamide-nitrile rubber blends and its influence on mechanical properties

Polyamide-nitrile rubber blends of high polyamide content (100/0, 70/30, 50/50) were prepared by melt mixing in a Haake Rheocord. The diffusion of water through the blends was investigated at various temperatures; 28, 45, 65 and 75 degreesC. The temperature dependence of the diffusion characteristics indicates that the transport mechanism varied with blend composition, morphology and temperature. The weight gain curves for pure polyamide and blends rich in polyamide showed a maximum followed by a decrease (overshoot effect). The enthalpy and entropy of sorption have been computed from the sorption data. Transport was found to follow the Fickian type mechanism. The effects of water uptake on the mechanical behaviour of the blends have also been analysed. The mechanical properties were found to decrease considerably as a result of water absorption.