Material Science of Plastics
Polyethylene is produced by the polymerization of the gaseous substance ethene. The density of the material can be influenced by means of different synthesizing processes, creating the following three types: HD-PE (High-Density-PE), LLD-PE (Linear-Low-Density-PE) and LD-PE (Low-Density-PE).
Essentially, PE is a rather soft plastic that displays a high level of stability towards chemicals. As PE hardly absorbs any water and has a low density, in water it floats on the surface.
HD-PE / bottle crates, barrels, bottles and mini-bottles, buckets, bowls
LD-PE, LLD-PE / wrapping foils, plastic bags, cable sheaths, tubes
Polypropylene – also known as polypropene – is a thermoplastic derived from the gas propene. This plastic is often worked into fibers
PP is the mass plastic with the lowest density. It, too, floats on the surface when in water. Its stability and resistance to chemicals is similar to that of LD-PE. However, PP can be used under greater heat. As PP is odorless and does not cause skin irritation, it is widely used in the food and pharmaceuticals industries.
Food packaging, electrical household appliances, parts in the automotive industry, building, garden furniture, artificial lawns, suitcase shells, medical appliances, plastic bags
Polyvinyl Chloride (PVC)
Polyvinyl chloride is produced from the gas chlorothene, known as vinyl chloride. By adding plasticizers this originally hard, stiff plastic becomes elastic. The phthalates used as plasticizers in PVC can amount to anything up to 70% of the material.
PVC is a very robust, insulating plastic that it is difficult to set fire to, making it an ideal material for the building industry, in particular for pipes and window profiles. In health terms, on the other hand, PVC is far from harmless: from the carcinogenic base material to the phthalates that are injurious to health, and poisonous dioxins that are released when it burns.
Flooring, drainage pipes, window profiles, seals, tubes, records, baby goods, swimming rings
Polystyrene is produced from the colorless liquid styrene. In a foamed state this plastic is known under the trade name Styrofoam.
PS has a glass-like, shiny surface. It is hard and brittle, which can lead to the formation of tension cracks. In a foamed state the material is used above all as thermal insulation. PS is problematic on account of carcinogenic materials, above all in the production and processing. In addition it also is difficult to recycle.
CD jewel cases, electric cable insulation, casings for electrical appliances, yoghurt containers, packaging foils, thermal insulation, insulating packaging material
Polyurethanes are the product of the polyaddition of isocynates (ester) and diols (divalent alcohols). Depending on the method of production this group of plastics can display very different qualities.
PU is frequently produced as a foamed material. The soft foam that retains its shape is suitable above all for upholstered furniture, whereas the hard foam is used on the building site. This plastic can, however, also be processed to make paints, adhesives or elastic textile fibers. However, it is difficult to recycle and if burned releases poisonous substances (isocyanate, prussic acid).
Mattresses, car seats, kitchen sponges, thermal insulation, rust protection in the automotive industry, coatings for furniture and floors, textiles (elastane)
Polyethylene Terephthalate (PET)
Polyethylene terephthalate is a polycondensate from the family of polymers that is produced from terephthalic acid and ethylene glycol.
In its amorphous state PET is a transparent, lightweight, impact-resistant material that is used above all to make bottles for soft drinks and water. PET is also processed to form textile fibers, it retains its shape, is crease and tear-resistant, and repels water. PET has a relatively good recycling balance. On the other hand the fact that PET bottles release acetaldehyde and antimony into the liquid they contain is problematic. However the values measured are not regarded as hazardous to health.
Bottles, packaging for food and cosmetics, household appliances, mechanical engineering, safety belts, medical implants
Polycarbonates also belong to the groups of polyesters and are generally produced from phosgene and bisphenol A. On account of its particular qualities PC is an important plastic but, as it is relatively expensive, it is used only where necessary and is not numbered among the mass plastics.
Polycarbonate is colorless and translucent. It has little resistance to chemicals, but on the other hand is highly resistant to knocks and does not splinter. Therefore PC is ideal for use in the area of optics and for safety glazing. However, as it contains the substance Bisphenol A this plastic is questionable in health terms.
CDs and DVDs, automotive industry, electronics, spectacles, protective helmets