Polyethylene resin refers to gases or liquids made up of a chain of ethylene monomers, small molecules that combine together in repeating patterns to form a large molecule called a polymer. Although the actual material is polyethylene resin, it is simply referred as polyethylene under most circumstances. It is a type of thermoplastic, commonly used for packaging, toys, plastic shopping bags, gas pipes, hose, tubing, and machine parts.

Ethylene is a hydrocarbon with the chemical composition of C₂H₄. Polyethylene resin has a formula of C_2nH_4n+2, where 'n' is the number of monomers that combined through the process of polymerization to form this chain. The process of polymerization turns the ethylene into a thermoplastic resin.

There are two types of resin, natural and synthetic. Natural resin is a hydrocarbon which is secreted by many plants especially by the coniferous trees. As its name signifies, synthetic resin is manufactured through a process called esterification. It is a chemical process involving an alcohol and an acid, which form a hydroxyl compound called ester. Both natural and synthetic resins are materials with high viscosity that are capable of hardening at a certain temperature.

Polyethylene resin has a number of variations, with names such as high density polyethylene (HDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), and so forth, based on density and crystallinity. Due to these different compositions, polyethylene resin has numerous uses in our daily lives and various industries. During the manufacturing process, the resin is injected into machines with specific pressure and temperature settings. The hardening property of resin helps to set the raw material as required.

PE, the abbreviation for polyethylene, is normally marked to indicate that plastic packaging or a plastic product was made from polyethylene resin. It also has the three arrow signs to indicate that it can be recycled. Most of the polyethylene products end up in the ocean or landfills, however. With more than 60 million tons of the material being produced annually all over the world, the usage of polyethylene resin has become a serious environmental issue.

Currently, studies are being carried out to produce biodegradable polyethylene resin to overcome the environmental issue. In terms of polyethylene resin usage, recent medical research has indicated the possibility of using HDPE to create implants for facial deformities. Cross linking of ultra high molecular polyethylene (UHMWPE) is being considered to improve the problem of wear on current total joint replacement devices.