Polyethylene Foam is the most well-known plastic material, produced at more than 85 Mt per year. It is the simplest of the commercial polymers, only made up of chains of CH2 groups. It’s the same polymer which is used to make plastic bags from supermarkets, milk bottles, many toys and even bulletproof vests. This material has varied uses as well as a very simple structure resulting from the coupling of a large number of ethylene molecules.
The Polyethylene Foam at its Beginning
Polyethylene (PE) was prepared in 1898 by Hans von Pechmann, a German chemist who obtained it by heating unstable and toxic diazomethane CH2N2 with the release of dinitrogen. This waxy product was subsequently characterized as being polymethylene. Later, two British chemists from Imperial Chemical Industries (ICI), Eric Fawcett and Reginald Gibson, accidentally discovered the first practical synthesis of polyethylene by using a more easily accessible molecule named ethylene, C2H4. By heating under high pressure a mixture of ethylene and benzaldehyde in the presence of traces of oxygen, they obtained a white, waxy material. This reaction was understood in 1935 and then developed by ICI which started to manufacture polyethylene with a density of 0.95 and other interesting properties. It is said that the use of this material as insulation for the wires and cables used in early radar installations contributed to the British victory at the Battle of Britain.
The Polyethylene Foam: the Next Years
The search for milder conditions of temperature and pressure for the polymerization of ethylene led in the 1950s to the development of catalytic systems based on transition metals. Chromium trioxide was indeed discovered in 1951 by Robert Banks and J Paul Hogan at Phillips Petroleum (United States). In 1953, Karl Ziegler made combinations of titanium chlorides and organoaluminum reducing compounds at the Max-Plack Institut für Kohlenfoschung (Germany). Karl Ziegler’s seminal work on the transition metal-organoaluminum salt combinations has earned him the Nobel Prize in Chemistry, shared with the itapdf Giulio Natta. A third type of catalytic system, based on the combination of a particular family of organometallic complexes, the metallocenes, and new organometallic reducers, the alkylaluminoxanes, was discovered in 1976 in Hamburg by Walter Kaminsky and Hansjörg Sinn. The search for new catalytic systems is still current and leads to extremely efficient catalysts, capable of producing several tones of PE per gram of catalyst! Anyway, polyethylene foam is now very popular in manufacturing industries and Novostrat is one of the best manufacturer in Europe.