What is polyethylene (PE)?

The semi-crystalline thermoplastic polyethylene is obtained from the polymerization of ethylene. A distinction is made between the low-density(LD) and the high-density (HD) form. Due to the strong branching between the polymer chains, LDPE is difficult to crystallize and therefore has a low density. HDPE, on the other hand, consists of linear polyethylene chains that can crystallize with a high density. The density of LD-PE is in the range of 0.920 – 0.940 g/cm³ with a crystallinity of 20 – 40 %. The density of HD-PE is in the range of 0.940 – 0.970 g/cm³ with a crystallinity of 40 – 80 %. Like other polyolefins, PE has low water absorption. LDPE is significantly softer and more flexible than the related HD variant. Other properties are largely determined by the density and the degree of polymerization. In general, it can be said that the higher the density, the higher the melting temperature, impact strength and yield stress, but the lower the swelling behavior and permeability. It is also very chemically resistant and has good electrical insulation. An increase up to ultra high molecular weight (UHMW) can further improve the properties and also increases abrasion resistance and wear resistance. We encounter polyethylenes everywhere in everyday life, and also in machines. Due to their physiological harmlessness, they are also frequently used in the food industry.