The Scientific and Technological Route to the Manufacture of High-Modulus Polyethylene

Abstract

Polyethylene has been manufactured commercially for over sixty years. However recently a high-modulus variant has become available. This article describes the background to the development of high-modulus polyethylene and describes the story behind the sequence of scientific discoveries and technological developments that occurred to enable this advance.Polyethylene was discovered by accident in the 1930s when two scientists working for the ICI chemical company carried out a series of experiments to study the effect of pressure on the reaction kinetics of certain organic liquids and gases. During these experiments, the scientists noted a waxy deposit in their small reaction vessel which marked the birth of one of the world's largest commodity polymers. The crystallographic structure of polyethylene was determined by another ICI industrial scientist who at the time was pioneering x-ray techniques. The crystallography of polyethylene, shown in Figure 1, is relatively simple in that it shows the long CH2-CH2 polymer chains packed in the all “trans” configuration to form an orthorhombic cell.Polyethylene rapidly developed as a commodity thermoplastic finding application in injection molding, extrusion, and packaging. Its prime material characteristics are its toughness, flexibility, and ease of processing. The stiffness of the polymer for most applications was found to be of the order of 1 GPa, which was similar to other thermoplastics but less than metals such as aluminum at 60 GPa and steel at 210 GPa.