Polyethylene
Introduction
Polyethylene (PE) is a versatile polymer used in a variety of applications from packaging to automotive components. It is a type of polyolefin, which is a high-growth sector of the global plastics industry. Polyethylene is the most widely used plastic, with an annual production of approximately 80 million metric tons.
History
Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while heating diazomethane. The material did not become a market success until the 1930s when it was rediscovered by researchers at the Imperial Chemical Industries (ICI) in the United Kingdom.
Structure and Properties
Polyethylene is a long-chain polymer of ethylene (ethene). It is composed of repeating ethylene monomer units, with the chemical formula (C2H4)n. The properties of polyethylene depend largely on the length of the polymer chain and the degree of branching.
Low-Density Polyethylene (LDPE)
Low-Density Polyethylene (LDPE) is a highly branched form of polyethylene with a low tensile strength but high ductility. It is used in applications where flexibility and transparency are important, such as plastic bags and film wrap.
High-Density Polyethylene (HDPE)
High-Density Polyethylene (HDPE) is a linear form of polyethylene with little branching, resulting in a more rigid and opaque material with a higher tensile strength than LDPE. It is used in applications where rigidity is important, such as plastic bottles and piping systems.
Production
Polyethylene is produced through the polymerization of ethylene, a gaseous hydrocarbon. There are several methods of polymerization, but the most common are high-pressure polymerization, used for LDPE, and low-pressure polymerization, used for HDPE and Linear Low-Density Polyethylene (LLDPE).
Applications
Polyethylene is used in a wide range of applications due to its versatility. Some of the most common uses include packaging (plastic bags, plastic films, geomembranes, containers including bottles, etc.), piping systems, toys, playground slides, plastic surgery (prosthetic devices, implants, etc.), and insulation for wires and cables.
Environmental Impact
Polyethylene, like all plastics, has an environmental impact. It is non-biodegradable and can take hundreds of years to decompose in the environment. However, it is recyclable and many initiatives are in place to increase the recycling of polyethylene products.