Polyethylene

By far the most popular thermoplastic commodity used in consumer products (especially products created by rotational moulding), polyethylene is created through the polymerization of ethylene (i.e., ethene).

Chemical Composition

The ethylene molecule is C₂H₄   (CH₂=CH₂)

Ethylene

Polyethylene Polymer

A.K.A.

Polyethene, Polythene, PE, LDPE, HDPE, MDPE, LLDPE

• LDPE (Low Density Polyethylene) is defined by a density range of 0.910 - 0.940 g/cm³. It 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. LDPE is created by free radical polymerization. The high degree of branches with long chains gives molten LDPE unique and desirable flow properties.
• HDPE (High Density Polyethylene) is defined by a density of greater or equal to 0.941 g/cm³. HDPE has a low degree of branching and thus stronger intermolecular forces and tensile strength. HDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts. The lack of branching is ensured by an appropriate choice of catalyst.
• MDPE (Medium Density Polyethylene) is defined by a density range of 0.926 - 0.940 g/cm³. MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts.
• LLDPE (Linear-Low Density Polyethylene) is defined by a density range of 0.915 - 0.925 g/cm³. is a substantially linear polymer, with significant numbers of short branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (e.g. 1-butene, 1-hexene, and 1-octene).