Polyethylene

Very widely used, low-priced plastic from the polyolefines family with linear polymer chains. Usually used in a non-modified and non-filled form, it is readily recyclable and harmless. For this reason, it is widely used as packaging material also for food. Highly combustible with high energy release (comparable to mineral oil). Non-polar, therefore low surface tension. Before gluing, printing or painting, activation is required. Despite the simple structure, there are groups with highly different material properties. The primary distinctive feature is the molecule mass. Generally, PE forms extremely long-chain giant molecules of between 300,000 g/mol (LLDPE=Linear Low Density PE) and several million g/mol (UHMWPE=Ultra High Molecular Weight PE). While LLDPE, a mass plastic that is very easy to process, is mainly used in extrusion, the melt of UHMWPE is hardly flowable and extrusion and injection moulding are no longer possible at the extremely high molecular weights. This material is fit for sintering only, which makes the production of moulded parts very expensive. UHMWPE is used for some applications mainly due to its extremely good abrasion behaviour. The strength of PE is not very high, but can be greatly increased by stretching, which not only aligns but also stretches the molecules. Then, extremely high-strength textile fibres can be produced (Dyneema, Spectra).