An experimental study of thermal post-production processing of auxetic polypropylene fibres

Following the successful batch production of auxetic ultra high molecular weight polyethylene, polypropylene and nylon, in the form of 10 mm diameter cylinders, a continuous melt extrusion route was adapted from conventional melt extrusion routes to produce fibres. Previous studies have shown that, once drawing has occurred, the auxetic effect is lost and, consequently, the mechanical properties of these fibres have been restricting their otherwise great potential in a wide range of applications. Research has therefore been undertaken into improving this matter by subjecting the auxetic fibres to a range of different thermal post-production processing conditions. The fibres then underwent mechanical testing, Differential Scanning Calorimetry and Video Extensometry. Results suggest that annealing enhances the mechanical properties of these fibres and may provide a further route to enhancing auxeticity in improving homogeneity by over 40%.