Novel variations in the microstructure of the auxetic microporous ultra-high molecular weight polyethylene. Part 1: Processing and microstructure

Recent publications have detailed how auxetic (negative Poisson's ratio) polymers have been fabricated by a novel thermal processing route consisting of three well-defined stages-compaction, sintering and extrusion. In this paper, the compaction stage of the processing route is omitted and the effects of this on the structural integrity, microstructure and Poisson's ratios of the extrudates examined. The effects of varying the processing parameters of the sintering and extrusion stages are studied so that a set of conditions that produce a highly fibrillar auxetic material with sufficient structural integrity to allow mechanical properties to be evaluated can be defined. Poisson's ratios as low as -4 have been obtained.