Polyethylene is the world’s most widely used thermoplastic and is made by the polymerization of ethylene. Polyethylene is often classified by its density, because greater density corresponds with greater material rigidity.
The world’s largest volume polyethylene is high density polyethylene (‘HDPE’), which has a relatively high degree of tensile strength. Plastic containers represent the most common household use of high-density polyethylene. At the opposite end of the spectrum is low density polyethylene (‘LDPE’), which was the first type of polyethylene to be developed. Flexible packaging represents the most common household use of low-density polyethylene. Both high- density polyethylene and low-density polyethylene are also commonly used for moulding applications. Linear low-density polyethylene (‘LLDPE’) can usually be manufactured at a slightly lower cost than low density polyethylene and has similar basic properties. While low-density polyethylene and linear low-density polyethylene are to a certain extent substitutable for each other, one may be more suitable than the other for a specific application.