22-9-21
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Polyethylene, radar, and submarine cables
"They had heated a mixture of ethylene and benzaldehyde to 170°C (338°F), using apparatus that could submit materials to a pressure of 1,900 atmospheres (1,925 bars). But the reactions were explosive and safety concerns prompted the now defunct ICI, which merged into Dutch-based Akzo Nobel, to halt the research.
In December that year, Williams and colleagues Michael Perrin and John Paton reinvestigated the experiments of Gibson and Fawcett using ethylene alone. Under similar experimental conditions - but with better equipment - they observed a pressure drop, and when the reaction finished there were 8.5g of white PE powder.
Williams, Perrin and Paton had been lucky. The vessel had leaked and, it was later confirmed, a trace of oxygen was present in the fresh ethylene that had been added to the reaction vessel to replace the leaked gas. The fresh ethylene contained, by chance, the right amount of oxygen to act as an initiator.
"For once it didn't explode - usually it did - and we thought something must be wrong. So we left it to cool overnight. And when I looked inside the metal container the next day, I found what looked like a lump of sugar. In fact, that 'sugar' was polythene."
Uses for early PE were limited, as the material was soft and had a low melting point. This was because under the high pressure polymerization process the ethylene molecules did not always add in a regular chain.
A member of ICI's dyestuffs division, Bernard Habgood, recognized that PE could supersede gutta-percha, a natural material, for insulation of submarine cables. This provided the impetus to proceed to commercial scale production. The first full-scale PE plant, with a 100 tonne/year capacity, went into production on September 1, 1939, the day Germany invaded Poland and war became unavoidable for Britain.
ICI's work on PE changed during the Second World War, when the material was used to insulate airborne radar equipment. During the development of radar in the early war years it had proved difficult to insulate the equipment to prevent power loss and thus preserve the strength of the signal. PE's electrical insulation properties enabled the British forces to reduce the weight of radar equipment and allowed them to place radars inside fighter planes. This provided an enormous technical advantage in long-distance warfare, most significantly in the Battle of the Atlantic against German submarines. The Germans were obliged to use a bulkier insulating material for their radar, which was less effective."
http://www.icis.com/resources/news/2008/05/12/9122447/polyethylene-discovered-by-accident-75-years-ago/
https://en.wikipedia.org/wiki/Polyethylene .
http://www.polymer-search.com/inventionplastic.html .
http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/polypropylene.html .
http://www.independent.co.uk/news/science/polythenes-story-the-accidental-birth-of-plastic-bags-800602.html .
