a macromolecular compound of the general formula
that forms during polymerization or copolymerization of unsaturated olefin hydrocarbons (R, R′ = H, CH3, C2H5, and so on). The best-known olefin polymers are polyethylene (R = R′ = H) and polypropylene (R = H, R′ = CH3).
Olefin polymers are characterized by high crystallinity, which imparts satisfactory mechanical strength, high dielectric constants, and resistance to the action of corrosive substances (with the exception of strong oxidizing agents, for example, HNO3). However, they have low adhesion to metal and other surfaces. To improve adhesion, polar groups, such as >CO and—COOH, are introduced into the macromolecules by copolymerization or treatment of the polymers. This makes it possible to extend the use of olefin polymers.
Olefin polymers are unequaled among thermoplastic materials in the scale of their industrial production and their wide range of uses as films and fibers, electrical insulation coatings, and molded objects. Important industrially produced olefin polymers include not only polyethylene and polypropylene but also their copolymers, ethylene-propylene rubbers. The importance of these rubbers comes both from their valuable technical properties and from the availability of cheap petrochemical raw materials (ethylene and propylene).
In 1973, world production of polyethylene was about 10 million tons, and production of polypropylene was about 2.4 million tons. Polyisobutylene (R = R′ = CH3), as well as copolymers of isobutylene (for example, butyl rubber), is of industrial significance.
Poly-l-butene is produced on a small scale in the USA and the Federal Republic of Germany; it is characterized by the absence of creep and is used for the production of pipes. Highly heat-stable olefin polymers are also produced—for example, poly-4-methyl-l-pentene, which is produced in Great Britain and the USA and has a Vicat softening point of 180°C. A method has been developed in the USSR for the production of polyvinylcyclohexane, with a Vicat softening point of 225°C. Polymers of this type are promising materials for a number of uses in medicine and radio electronics.
REFERENCES
See references under .B. A. KRENTSEL’
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