Polymers are long chains of repeating molecules, or monomers, held together by covalent chemical bonds. In most cases, the number of repeating monomers is very large, as much as hundreds of thousands.
Polymer nomenclature is generally based upon the type of monomers comprising the polymer, for example, polyethylene from ethylene, polypropylene from propylene, etc. Polymers that contain only a single monomer are known as homopolymers (e.g. polystyrene) while polymers containing a mixture of monomers are known as copolymers (e.g. ethylene-vinyl acetate). Synthetic polymers can be thermoplastic, i.e. repeatedly softened on heating, or thermoset, i.e. softened only once.
Polymers can be formed into different shapes by moulding or extrusion processes to make structural components. They can be formed into filaments or threads to make textiles, carpets, yarns and ropes, and they can be made into elastomers which return into their original shape after being extended or compressed by force. They are also used in paints and coatings, adhesives and lubricants.
The main commodity polymers include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET) and polycarbonate (PC).
Synthetic rubber is a man-made polymer material which acts as an elastomer. Synthetic rubbers can be used as a substitute for natural rubber in many cases or when improved material properties are needed. They can be made by the polymerisation of a number of monomers including butadiene, isoprene and chloroprene. The two main synthetic rubbers manufactured from butadiene are styrene butadiene rubber (SBR) and polybutadiene rubber (BR).
Synthetic or man-made fibres can be produced from natural or synthetic materials. The fibres are created by forcing the fibre-forming material through holes to form threads. Polymer fibres, which are usually based on petrochemicals, can be made from materials such as polyamide/nylon, polyester and polypropylene.