a light-yellow synthetic rubber that is a polymer of chloroprene, with the general formula [—CH2—CCl=CH—CH2—]n. The density of polychloroprene rubbers varies from 1.20 to 1.24 g/cm3, and the molecular weight ranges from 100 × 103 to 200 × 103. The glass-transition temperature is –40°C, the volume electrical resistivity, 4.4 × 106 ohm· m, the electric strength, 23 megavolts/m, and the dielectric constant, 6.4 to 6.7.
Polychloroprene rubbers are characterized by a number of specific properties, determined by the presence of chlorine atoms in the macromolecules. These properties include resistance to oil, gasoline, ozone, and heat; incombustibility; and the ability to vulcanize through the addition of metallic oxides, for which purpose mixtures of ZnO and MgO are used in industry. Polychloroprene rubbers crystallize upon stretching, and consequently those that are uncompounded are most durable. When polychloroprene rubbers are compounded, their durability decreases in certain cases, but other valuable properties, such as tear strength and resistance to gasoline, usually improve.
Polychloroprene rubbers are synthesized industrially by polymerization in an aqueous emulsion. They are mainly used in the production of industrial rubber products, primarily conveyor and other types of belts and various hoses. They are also used in the production of wire and cable insulation and protective coatings. Polychloroprene rubber adhesives and chloroprene latexes are also important in industry.
The annual world production of polychloroprene rubbers amounts to approximately 400,000 tons. The most common trade names are Nairit in the USSR and Neoprene in the USA.
REFERENCESEntsiklopediia polimerov, vol. 3. Moscow, 1977.
See also references under RUBBER, SYNTHETIC.