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Polyethene: The Early Years

 
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Polyethene was first made in 1933 at ICI in England as part of a general study of how chemicals respond to pressure. Left in a high-pressure reactor over a weekend, the gas was found to have turned into a waxy solid. Unfortunately, the reactor blew up soon afterward, and work on the project was banned.

The prevailing opinion at the time was that polymerisation of ethene was impossible, but that did not stop ICI executives from sacking one of the pair that carried out these initial experiments when he carelessly mentioned it at a conference!

Not until 1936 did research secretly recommence with a new high pressure reactor. Experiments discovered that a small trace of oxygen was necessary to catalyse the polymerisation, and if the reactor used had not had a small leak it would have not generated polyethene - instead, due to other faults, it would have exploded catastrophically.


A high pressure reactor (Mettler RC1e) routinely used in the KCPC laboratories.

Polyethene was produced commercially from 1939 as a substitute for gutta percha (poly-trans-isoprene) as an insulator for coaxial cables, and played a key role in wartime by enabling radar sets to be built small and light enough to be carried on aircraft.

This material was LDPE - a branched PE of relatively low molecular weight produced at 300°C under a pressure of 15 to 35 MPa.

HDPE, a linear polyethene (the linear chains can pack together much more easily than branched ones to give a denser, more crystalline material) was produced independently by DuPont and the U.S. Rubber Company during the war, but was not commericalised.

At the end of the Second World War, the potential of polyethene was still unrealised; as one researcher said, contemplating the winding-up of the military production programme: "now we need to find out what to do with the stuff."