Polyethylene resin is a type of themoplastic that’s commonly used in the manufacture of things like plastic shopping bags, packaging, certain tubing and machine parts, and even a number of toys. It’s a flexible chemical composite that’s relatively inexpensive to manufacture and widely accessible. The “resin” part of the name is mostly in reference to the substance’s viscosity. It is made up of complex chains of ethylene monomers, which are small molecules that combine together in repeating patterns to form larger compounds known as polymers. Manufacturers and researchers typically heat the polymers in order to activate and manipulate them, though at room temperature most are solid and will almost always keep their shape. Some occur naturally, but most of those used in commercial applications are the result of synthetic manufacturing. There are many variations, and most of them can be recycled. Not all communities have recycling programs, though, and in most places plastics end up in landfills and elsewhere in the environment anyway. Plastics in the polyethylene family don’t biodegrade, and a number of environmental activists have voiced concerns about the continuing manufacture of products that use these materials.
Understanding Resins Generally
A resin, at least in science, is usually a thick liquid made up of complex polymers. Tree sap is a common natural example. Some polyethylenes occur naturally like this, typically as a byproduct of petroleum burning or pooling and evaporating off. More commonly, though, it’s created synthetically in a laboratory. The resins can be poured into molds or combined with other materials to fix their form, then they are either heated or cooled in order to form a solid.
At room temperature they tend to be very stable, and are often used for foods and beverages for this reason. Most consumers never see the plastic in its resin form. Perhaps for this reason, it’s simply referred to as “polyethylene” in most circumstances.
From a Chemical Perspective
Ethylene is a hydrocarbon that carries the chemical formula C2H4. Polyethylene resin has a formula of C2nH4n+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 that is secreted by plants and other natural earth processes. 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.
This sort of 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, this resin has numerous uses in the home and in 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.
Recycling and Environmental Issues
PE, the abbreviation for polyethylene, is normally marked to indicate that plastic packaging or a plastic product was made from a resin. It also has the three arrow signs to indicate that it can be recycled. Most of the polyethylene products manufactured around the world 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.
Studies are being carried out in many parts of the world to produce biodegradable polyethylene resin to overcome the environmental issue. In terms of polyethylene 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 also being considered to improve the problem of wear on current total joint replacement devices.