the World’s No. 1 Plastic
by Robert H. Olley
University of Reading Polymer Physics Centre
J. J. Thomson Physical Laboratory, Whiteknights,
Reading RG6 6AF, England
last update: 27/Dec/2007
I was first prompted to write this article after reading a student thesis on the use of Intermediate
Technology (IT) in Building Design. One of the pressures forcing the business to use IT is the
increasing number of materials and varieties of any given material that are available for
construction. The greatest single change since the Second World War is the introduction of
Plastics. However, few people appreciate the great variety of plastics there are. Even among
those who are aware of the difference between polyethylene (better known as polythene), PVC,
and polystyrene, very few indeed realize how many different varieties of polyethylene there are.
(My own interest in this is that the major part of my own research is devoted to preparing
specimens of polyethylene and similar materials for examination of their micro-crystalline
structure under the electron microscope. Before I continue, I must apologize to chemists for
over-simplifying matters, but I would encourage economists to read on. Do not let the little bit
of simple chemistry put you off, for there is much about the market as well!)
The story of polyethylene really starts in 1932. Britain, along with the whole industrialized
world, was in deep recession following the Wall Street Crash of 1929. It was difficult to find
money for large-scale research, and yet something new was needed. In ICI, there was suggested
a research program to look for new reactions under extreme pressure. Fifty different reactions
were tried, all without success - but one of the failures resulted in the discovery of polyethylene
through a remarkable series of coincidences.
One of the suggested mixtures had included ethylene, a very light gas prepared from petroleum.
The reaction hoped for had not occurred, but instead there was a white waxy solid on the walls
of the reaction vessel. Analysis showed that this must have formed from the ethylene alone. In
1935, the reaction was tried again without the other component, but this time the vessel leaked;
nevertheless, some more polyethylene was obtained. At this time, ICI management made the
very bold decision to start a major development programme, on the basis of only 8 grams
obtained of the promising product! So they tightened up their procedures, and as a result - no
polyethylene! It was only after months of work that they realized that oxygen had to be present
in some form, either from air leaking in, or, in the first experiment, indirectly from having
reacted with the other component of the original mixture. These two “happy accidents” had
allowed polyethylene to be produced.
