What Does Polyethylene Mean
We explain what polyethylene is, the main properties it has and the different uses of this famous polymer.
What is Polyethylene?
It is known as polyethylene (PE) or polymethylene to the simplest of the polymers from chemically composed of a linear unit and repetitively atoms of carbon and hydrogen. It is one of the most economical and simple to manufacture plastic materials , which is why approximately 80 million tons are generated annually worldwide.
The manufacture of polyethylene is made by various polymerization processes , either by free radical processes using anionic, cationic or coordination of ions . Depending on the type of reaction chosen, a different form of the same plastic will be obtained .
This material was first obtained by the German chemist Hans von Peachmann in 1898, due to an accident during diazomethane cooking. It was not until 1933 that it was intentionally synthesized, and chemists Reginald Gibson and Eric Fawcett did it 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 cheaper) using catalysts during the reaction and obtaining a higher density polyethylene. Such a discovery resulted in the development of the Ziegler-Natta catalysts, which made them winners of the Nobel Prize in Chemistry in 1963.
See also: Lead
Polyethylene properties
Polyethylene is chemically inert, that is, it is almost non-reactive, and it has a whitish and translucent appearance. Tenacious and flexible at room temperature , it has a soft and scratchable surface.
Its melting point is 110 ºC and if it is reduced below its room temperature, it gains in hardness and brittleness. In the liquid state, polyethylene behaves like a non-Newtonian fluid, that is, its viscosity is not constant but depends on the temperature and if a shear stress is applied to it. Its viscosity decreases at higher temperatures and has a density of 0.80 g / cm 3 at about 120 ºC.
Polyethylene is not a good conductor of heat or electricity and its density (in solid state) varies with temperature. In general terms, the mechanical properties exhibited by the material will depend on the thermal history of its manufacture, that is, on the specific way in which it has cooled and solidified.
Uses of polyethylene
Polyethylene is an extremely versatile plastic with which many items can be made, such as:
- Plastic bags of all kinds.
- Films for packaging of all kinds of food , drugs and agro-industrial products.
- Hermetic containers for home use.
- Pipes for irrigation.
- Knobs, tubes, coatings.
- Kitchen film (plastic wrap).
- Containers for detergents, shampoo, bleach, etc.
- Mechanical parts, chain guides.
- Baby bottles, toys, disposable diaper base.
- Water buckets and drums.
- Covering of lagoons, channels, water tanks, etc.
- Manufacture of wood flour compound.
- Raw material for rotational molding.
- Cables, wires, pipes.