Drawing behaviour, mechanical properties and structure of poly( p-phenylene sulphide) fibres

Abstract

Poly( p-phenylene sulphide), (PPS), in the form of a multifilament spun yarn, was drawn over a heated roller (the pin) to a range of draw ratios from 1.26 to 4.8 at various pin temperatures from 70°C to 100°C. Annealed samples were also prepared using a second high temperature annealing zone in the drawing process, using a heated plate at temperatures between 150°C and 220°C. The maximum birefringence achieved was 0.270 compared with a theoretical maximum of 0.330 calculated from bond polarizabilities and bond angles suggesting that the drawing process conditions were close to optimization. From birefringence, shrinkage, and shrinkage force measurements average molecular network parameters were derived and in the light of these parameters the mechanical properties of oriented PPS fibres are compared with the mechanical properties of poly(ethylene terephthalate), (PET), and poly(ethylene methylterephthalate), (PEMT), fibres. The network parameters suggest that the PPS network has a higher density of entanglements than PET, connected by stiffer chains with fewer random links. However, recent measurements of the crystal modulus of PPS suggest that the planar zig-zag conformation of the molecule is responsible for the lower modulus of 8 GPa for PPS yarns compared with 16 GPa achieved with PET, rather than failure to achieve a sufficiently high molecular orientation.