Polybutylene terephthalate, PBT
PBT is characterised by high strength, stiffness and hardness. The material also has good friction and wear properties. Poor moisture absorption provides little suffocation (dimensionally stable) and uniform electrical properties over a wide temperature and humidity range. Recycling of discarded items and inlets is usually possible, although one must be aware that PBT can be degraded because of either critical processing or hydrolysis. If the material is handled appropriately during the first processing, it has been found in practice that 25% ground material can be added to new material without substantial modification of the original characteristics. Naturally, it is imperative that both new and ground material have a low moisture content.
This is a polymer of methyl methacrylate. It can be injection moulded, thermoformed and moulded from the monomer. A well-known trade name is Plexiglas. PMMA is available in light to viscous variants with different properties, such as high impact strength and surface gloss. It is very weather resistant and stable in UV light. PMMA is used for television screens, skylights, signs, displays, aircraft windows, lamp glass, watch glass, bathtubs, washbasins, vehicle headlights and other places where transparency and outdoor use is desirable. It is used in the optical and medical industry for eyeglasses, lenses and diagnosis equipment.
Polyethylene terephthalate, PET
PET is a thermoplastic product in the polyester family. The material is known for its good strength and rigidity and it is a good barrier against oxygen and carbon dioxide. It is available both crystal clear and opaque. It also has good resistance to impacts, has a hard surface and is easy to recycle. PET is commonly used as packaging, particularly for foods (e.g. beer and soft drinks) and non-food products because of its strength, thermal stability and transparency. It is also inexpensive, lightweight, shatter-proof and recyclable. Recycled PET can be used to make many new products, including fleece jackets, fibre filling for sleeping bags and down jackets, industrial tapes, sheet and film, automotive parts such as bumpers, grilles and door panels, and new PET containers for both food and non-food products. PET is available in two forms: A-PET, which is amorphous and transparent, and C-PET, which are part-crystalline and opaque. Bottles are amorphous and therefore transparent, whereas packaging for microwaves are crystalline and therefore opaque.
Polyvinyl chloride, PVC
PVC has been in use for more than 50 years and, due to its technical characteristics, it is widely used. Whereas other plastic materials are mainly produced from crude oil, PVC is manufactured using crude oil and salt (sodium chloride). The production process uses 57% salt and 43% oil. PVC products can be roughly divided into two main groups: hard PVC and soft PVC. Examples of rigid PVC products include pipes, windows, cable trays and profiles. Examples of soft PVC products include flooring, insulation of electric cables, medical equipment and tarpaulins. Hard PVC represents about two-thirds of PVC consumption, while the rest are soft or flexible products, as they are also known. What distinguishes the soft from the rigid PVC products is that only the soft products contain plasticisers. There are different types of plasticisers. PVC contains chlorine, which is released when PVC burns. Chlorine reacts with water vapour to form hydrochloric acid, which is harmful to nature in large quantities. In combustion facilities, the chlorine is neutralised by means of lime in order to avoid acidification of the environment. Rigid PVC products are suitable for recycling. In 1998, the recycling company WUPPI A/S was established by 5 major Danish manufacturers of PVC products. Thus, the collection and recycling of PVC was systematised to greater extent with a nationwide scheme (see www.wuppi.dk). WUPPI collects all the hard PVC building products.
Polycarbonate/acrylonitrile-butadiene-styrene, PC/ABS is a blend of PC and ABS, which provides a unique combination of high processability of ABS with PC’s excellent mechanical properties, impact resistance and heat resistance. The balance between the properties of PC/ABS are controlled by the relationship between PC and ABS in the mixture, the polycarbonate’s molecular weight and the blend of additives. The ratio of polycarbonate to acrylonitrile-butadiene-styrene mainly affects the heat resistance of the final product. PC/ABS mixtures exhibit a synergistic effect, resulting in an excellent impact strength at low temperatures that is better than the impact strength of ABS or PC
PEEK is a semi-crystalline material that is used where there are high demands for mechanical strength, temperature and chemical resistance. PEEK can be gamma-sterilised and is therefore used for medical instruments. In addition, it is often used as an alternative to metals such as stainless steel and titanium.
PSU is an amorphous transparent plastic with a yellowish tinge. It is often used in places where transparency is required. PSU has good hydrolysis properties and reasonably good chemical resistance and high temperature resistance. The material is characterized by good strength, rigidity, dimensional stability and good electrical insulating properties. It is usually used in the electronics, automotive and aerospace industries and in household equipment.