The structure and properties of oriented chainextended polyethylenes

Abstract

Highly oriented polyethylene can be produced by a route which involves firstly annealing the material at a pressure of 450 MPa and a temperature 234 ° C so that ideally it enters the intermediate phase and chain extended material is produced. This is followed by hydrostatic extrusion of the material to align the molecular chains.

The apparatus and procedure for processing the material by this route is described. The products produced both before and after hydrostatic extrusion have been structurally analysed and the density, orientation and DSC characteristics of two polyethylene materials are presented. The mechanical behaviour of the extrudates has been determined, particularly in terms of their dynamic bending modulus (E) and shear modulus (G). To aid understanding, an aggregate model has been developed which shows a linear relationship between 1/E and 1/G. The dynamic experimental results show good agreement with this model and the structural data adds further support to the findings.