Acrylic Rubbers

synthetic rubbers obtained by copolymerizing esters of acrylic acid with various unsaturated compounds. Of great interest are the copolymers of butyl acrylate with acrylonitrile:

(—CH₂—CH—CH₂—CH—)_n

COOC₄H₉CN

Acrylic rubbers are readily soluble in hydrocarbons and hydrocarbon derivatives but unstable in the presence of alcohols and glycols and during heating in moist media. These rubbers retain their properties during prolonged storage in darkness and in the presence of sunlight and ozone; they resist oxidation at high temperatures.

Acrylic rubbers are vulcanized with the aid of amines (most often triethylenetetramine and triethyltrimethylene-triamine in combination with sulfur), phenol-formaldehyde resins, and others. The tensile strength of acrylic rubber materials is approximately 10 meganewtons/m² (100 kg force/cm²); elongation per unit length is 300–400 percent; and brittle temperature is -25°C. The merits of such rubbers are high stability in ozone and light, stability of color in white and pastel tones, low gas permeability, and high resistance to enlargement of cuts upon bending. The shortcomings are low resilience at ordinary temperature (approximately 5 percent) and low resistance to frost.

Acrylic rubber products are resistant to the action of petroleum-based solvents and animal and vegetable oils; however, they swell perceptibly in solvents of the aromatic series as well as in alcohols and ketones. Their distinctive feature is resistance to the effects of sulfur-containing oils at high temperatures. Such rubbers can be used in contact with automotive vehicle oils. Acrylic rubber products are used primarily in the automotive industry in the form of various gaskets, sealing rings, small pipes, and so forth. They are also used for lining cisterns, gasoline tanks, and rubber shafts and in the preparation of heat- and oil-resistant transmission belts and conveyor belts.