On the microstructure and tensile strength of PC/ABS polymer blend joints

Large articles of polymeric materials which can not be molded require welding to join the components. Weld zones result in a morphology that differs from the adjacent areas. This difference in structure represents a defect in the article that can result in premature failure during service. Experiments with a Pulse 830 (a polycarbonate/acrylonitrile-butadiene-styrene blend) engineering resin showed that weld zones made using hot plate techniques, retained only 30% of the unwelded tensile strength, while 80% was retained if vibration welding was applied. Examination of the weld zone by transmission electron microscopy (TEM) revealed a dramatic difference in the microstructure.The weld zone morphology in Pulse" 830 engineering resin by hot plate welding is highly laminar and oriented while a much more homogeneous structure, similar to that in the bulk, is produced by vibration welding. This morphology difference accounts for the variation of the tensile strength of the joints.