An alternative method for processing high viscosity polymers. I. Development and feasibility study

Abstract

Ultrahigh molecular weight polymers generally exhibit very high melt viscosities. They are therefore very difficult to process and require heavy-duty processing equipment. In some cases they cannot be processed at all using conventional melt processing techniques. In this study, a novel processing method called Thermoflow Forming (TFF) has been developed for manufacturing parts made from high viscosity polymers. The TFF process is based on the flow of polymer material in its thermoelastic state, between its glass transition and melting temperatures, by compressive flow thermoforming. The processing equipment consists of an upper and lower mold tool, which may be driven together, while its temperature is controlled through either induction heating or air cooling. Parts with both constant and varying wall thicknesses were successfully manufactured from ultrahigh molecular weight polyethylene and polytetrafluoroethylene (PTFE). Despite the significantly different wall thicknesses molded, the parts showed minimal warpage and no voids. Those made from PTFE exhibited a fibrillated morphological structure whose size and orientation depended on the material flow direction.