Polyethylene. History of invention and production

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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
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Polyethylene. History of invention and production

The history of technology, technology, objects around us

Directory / The history of technology, technology, objects around us

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Polyethylene is a thermoplastic polymer of ethylene. It is an organic compound and has long molecules ...-CH2-CH2-CH2-CH2-..., where "-" denotes covalent bonds between carbon atoms. The most common plastic in the world.

It is a waxy mass of white color (thin sheets are transparent and colorless). It is chemically and frost-resistant, an insulator, not sensitive to impact (shock absorber), softens when heated (80-120 ° C), freezes when cooled, adhesion (sticking) is extremely low.

Structural formula of polyethylene

Bags in the supermarket, food packaging, plastic utensils, bottles, pipes, duct tape... All this and more is made from one material, the king of plastics - polyethylene.

It was opened twice and both times - completely by accident. This material was first obtained by heating diazomethane by the German chemist Hans von Pechmann in 1898. Then he simply did not pay attention to the unexpected result of his experiment - a wax-like residue at the bottom of the test tube. Polyethylene was discovered for the second time by Reginald Gibson and Eric Fawcett, chemists at the British company ICI. The department in which they worked was engaged in the study of new chemical reactions occurring at high pressures.

On March 27, 1933, Gibson and Fawcett pumped a mixture of ethylene and benzaldehyde into the reaction vessel at a pressure of 1900 atm and at a temperature of 170 °C. Suddenly, the pressure in the tank dropped - it turned out that the gases had turned into a white solid, polymerized ethylene. But attempts to repeat the experiment ended for the most part in resounding failures - an explosion and decomposition into hydrogen and carbon. It was not possible to consistently reproduce the conditions for obtaining polyethylene, and the company's management, fearing that one day the matter would not be limited to a soot cloud, closed the project.

Two years later, the head of the ICI research division, Michael Perrin, decided to look into the experiments of Gibson and Fawcett. Luck smiled at him: the very first experiment ended not with an explosion, but with the formation of polyethylene. But the subsequent ones again showed how elusive a new substance can be.

The riddle was solved by Oxford chemist Paul Hinshelwood, who discovered an unaccounted factor - the interaction with oxygen. In those days it was customary to hand over cylinders for filling gases with open valves, and a small amount of air remained in them. As a result, the concentration of oxygen in the gas mixture varied significantly in different cylinders. And the polymerization reaction turned out to be sensitive not just to the presence, but to the right amount of oxygen - if it was low, polyethylene did not form, if too much, it decomposed with an explosion.

Gibson, Fawcett and Perrin were incredibly lucky - they took cylinders with exactly the right concentration of oxygen. After the discovery of this fact, the rest became a matter of technology, and a few years later the industrial production of polyethylene was established.

Its first application was the use as electrical insulation of wires. However, the material left much to be desired - it was soft and fusible until the German chemist Karl Ziegler developed catalysts for the production of high density polyethylene.

Polyethylene
PE foam roll

From that moment on, the new material began its triumphant march, becoming the most massive plastic in the world: about 80 million tons of polyethylene are produced annually.

Author: S.Apresov

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