Polyethylene (Meaning and Explanation)

We explain what polyethylene is, the main properties it has and the different uses of this famous polymer.

What is Polyethylene?

The simplest of polymers from a chemical point of view, composed of a linear and repetitive unit of carbon and hydrogen atoms, is known as polyethylene (PE) or polymethylene. It is about one of the most economically manufactured plastic materials and simple, which is why approximately 80 million tons are generated annually throughout the world.

The manufacture of polyethylene It is carried out through different polymerization processes either through free radicals, through anionic, cationic processes or by ion coordination. Depending on the type of reaction chosen, a different form of the same plastic will be obtained.

This material It was first obtained by the German chemist Hans von Peachmann in 1898, due to an accident during the firing of diazomethane. It was not until 1933 that it was intentionally synthesized, and this was done by chemists Reginald Gibson and Eric Fawcett in England, applying a pressure of 1400 bar and a temperature of 170 ºC in an autoclave (a metal container that allows working at high pressures). The material they obtained is known today as low-density polyethylene.

In later years, Karl Ziegler and Giulio Natta achieved polymerization at lower pressures (and therefore more economical) using catalysts during the reaction and obtaining a higher density polyethylene. Such a discovery led to the development of Ziegler-Natta catalysts, which earned them the Nobel Prize in Chemistry in 1963.

Polyethylene properties

Polyethylene is chemically inert, that is, it is almost non-reactive, and has a whitish and translucent appearance. Tough and flexible at room temperature has a soft and scratchable surface.

Its melting point is 110 ºC and if it is reduced below its ambient temperature, it gains hardness and fragility. In the liquid state, polyethylene behaves like a non-Newtonian fluid, that is, its viscosity is not constant but depends on the temperature and whether a shear stress is applied to it. Its viscosity decreases at higher temperatures and has a density of 0.80 g/cm³ at about 120 ºC.

polyethylene It is not a good conductor of heat or electricity and its density (in the solid state) varies according to temperature. In general terms, the mechanical properties of the material will depend on the thermal history of its manufacture, that is, the specific way in which it has cooled and solidified.