Hydrostatically-extruded polypropylene

Abstract

Melt-extruded cylinders of polypropylene can be hydrostatically extruded in the solid-phase to give uniform, highly-oriented rods. The tensile and torsional moduli of such extrudate have been measured as a function of the amount of deformation. Values obtained after large deformations are greater than those previously observed for drawn fibres. Birefringence and X-ray diffraction measurements of orientation have been compared and used to assess uniformity, and to predict the moduli on the basis of a simple aggregate model. Although the changes in modulus at low deformation ratio were not inconsistent with the model, there is definite evidence that it is not applicable to highly-deformed samples.