A phenomenological study of the hot-tool welding of thermoplastics. Part I: Polycarbonate

A dual platen hat-tool welding machine, in which the temperatures of the tw o hot-tool surfaces can be independently controlled, was used to study the weldability of bisphenol-A polycarbonate. In these experiments, the outflow in the melting phase was controlled by means of stops, the thickness of th e molten film was controlled by the heating time, and the outflow during th e final joining phase was also controlled by displacement stops. Strength d ata for butt welds are reported for a series of tests - both on dried and u ndried specimens - in which the hot-tool surface temperatures, the heating times, and the displacement stop positions were varied, but the pressure wa s not. Weld strength data are reported for three specimen thicknesses. It i s shown that very high weld strengths can be achieved, even in the undried material. (C) 1999 Elsevier Science Ltd. All rights reserved.