Linear density polyethylene (LDPE), Very low density polyethylene (VLDPE) and Ethylene copolymers

Linear density polyethylene (LDPE) is defined by a density range of 0.910-.0940 g/cm3. Linear density polyethylene (LDPE) has a high degree of short and long chain branching, which means that the chains do not pack into the crystal structure as well. It has, therefore, less strong intermolecular forces as the instantaneous dipole induced dipole attraction is less. This results in a lower tensile strength and increased ductility. Linear density polyethylene (LDPE) is created by free radical polymerization. The high degree of branching with long chains gives molten Linear density polyethylene (LDPE) unique and desireable flow properties. Linear density polyethylene (LDPE) is used for both rigid containers and plastic film applications such as plastic bags and film wrap.

Very low density polyethylene (VLDPE) is defined by a density range of 0.880-0.915 g/cm3. Very low density polyethylene (VLDPE) is substantially linear polymer with hogh levels of short chain branches, commonly made by copolymerization of ethylene with short chain alpha olefins (for example, 1-butene, 1-hexene and 1-octene). Very low density polyethylene (VLDPE) is most commonly produced using metallocene catalysts due to the greater co-monomer incorporation exhibited by these catalysts. Very low density polyethylenes (VLDPEs) are used for hose and tubing, ice and frozen food bags, food packaging and strech wrap as well as impact modifiers when blended with other polymers. Recently much research activity has focused on the nature and distribution of long chain branches in polyethylene. In High density polyethylene (HDPE) a relatively small number of these branches, perhaps 1 in 100 or 1000 branches per backbone carbon, can significantly affect the rheological properties of the polymer.

Ethylene coplymers

In addition to copolymerization with alpha olefins, ethylene can also be copolymerized with a wide range of other monomers and ionic composition that creates ionized free radicals. Common examples include vinyl acetate (the resulting product is ethylene vinyl acetate copolymer, or EVA, widely used in atheletic shoe sole foams) and variety of acrylates (applications include packaging and sporting goods).