THE EFFECT OF THE PROCESSING PARAMETERS ON THE FABRICATION OF AUXETIC POLYETHYLENE .1. THE EFFECT OF COMPACTION CONDITIONS

A novel fibrillated particulate microstructure has been fabricated in ultra high molecular weight polyethylene (UHMWPE) that produces a negative Poisson's ratio (auxetic) material. The processing route involves compaction, sintering and extrusion of a UHMWPE fine powder. The first, compaction stage is examined in this paper in detail in order to ascertain the compaction conditions required to produce, as an end-product, an auxetic polymer and to assess the importance of this stage in the processing route. It was found that while part of the function of the compaction stage was to impart structural integrity to the processed polymers, the conditions for optimizing the production of auxetic UHMWPE were not identical to those for optimum structural integrity of the compact. Both sets of conditions were examined, with compaction pressure and temperature being the most important of the variables examined.