Processing of ultra-high molecular weight polyethylene by hot isostatic pressing, and the effect of processing parameters on its microstructure

The processing techniques available for ultra-high molecular weight polyethylene (UHMWPE) do not lead to a homogeneous material. The processed material exhibits particle boundaries (fusion defects) reflecting the powder flakes of the virgin resin. Hot isostatic pressing has been used in this study as a possible technique to produce a homogeneous, defect-free material, and to study the effect of processing parameters on consolidation and other properties. The extent of consolidation was determined by optical microscopy using thin sections, and by scanning electron microscopy using cryofractured and solvent-etched specimens. Processing temperature is the most important variable affecting consolidation; fusion defects can be eliminated by increasing the processing temperature. This is sometimes accompanied by the appearance of spherulties; however, the degree of crystallinity, melting point, and density remain constant. DMA results show that the molecular weight between entanglements increases and the entanglement structure changes with an increase in processing temperature. (C) 2004 Society of Plastics Engineers.