Role of Ultrahigh Molecular Weight Polyethylene during Rotation Extrusion of Polyethylene Pipe

Abstract

A small amount of ultrahigh molecular weight polyethylene (UHMWPE) was added to a PE matrix that was then processed into a pipe by a self-designed rotation extrusion system. The results showed that during the rotation extrusion of the PE pipe, the polymer melts helically moved forward in an off-axis direction to induce molecular orientation and shish-kebab alignment deviate from the axial direction. However, because of sufficient relaxation of oriented molecules at high temperature, numerous spherulites arose in the pure PE pipe. With the addition of UHMWPE, the flow character of the PE matrix was tailored so the molecular relaxation was suppressed and the flow effect on formation of shish-kebab was amplified, bringing about denser shish-kebabs off the axial direction in the PE pipe. As a result, a PE pipe with excellent resistance to slow crack growth was prepared.