divinyl-styrene rubbers, synthetic rubbers; products of the copolymerization of butadiene (I) and styrene (II) (or α-methylstyrene) with the general formula
Butadiene-styrene rubbers are obtained by the copolymerization of monomers in an aqueous emulsion at temperatures of about 5°C (low-temperature) or about 50°C (high-temperature). The content of bound styrene in butadiene-styrene rubbers is about 8, 23, or 45 percent. Butadiene-styrene rubbers are light yellow, with a density of 900-990 kg/m3 (0.90_0.99 g/cm3). They are soluble in aromatic and aliphatic hydrocarbons and are nonresistant to lubricating oils but fairly resistant to ketones and dilute and concentrated acids.
Sulfur is generally used to vulcanize butadiene-styrene rubbers. The most widely used accelerators are sulfenamide derivatives of 2-mercaptobenzothiazole. Rubber mixtures containing these accelerators are highly resistant to precuring.
Active carbon blacks are used as fillers of rubber mixtures based on butadiene-styrene rubbers.
Cured rubbers made from rubbers containing 8 percent bound styrene are highly elastic and frostproof, and rubber containing about 45 percent styrene is the strongest and most durable but not very elastic or frostproof (see Table 1).
Some butadiene-styrene rubbers produced on a large industrial scale are filled with mineral oil or black during the manufacture of the rubber. The use of filled butadiene-styrene rubbers significantly facilitates their processing and yields savings while retaining fairly high-quality technical properties.
The types and brands of butadiene-styrene rubbers manufactured in the USSR and many foreign countries are highly varied. The most common are unfilled and oil-filled butadiene-styrene rubbers of low-temperature polymerization, containing about 23 percent bound styrene. Butadiene-styrene rubbers are all-purpose rubbers used to manufacture most rubber articles, especially automobile tires and inner tubes.
The industrial output of butadiene-styrene rubbers is about 50 percent of the total synthetic-rubber output capability. The capitalist countries produce more than 3 million tons a year.
|Table 1. Properties of cured rubbers from black-filled mixtures based on domestic butadiene-styrene rubbers (SKS-copolymers with styrene; SKMS-copolymers with α-methylstyrene)|
|sks-10 or skms-10 (˜8)1||sks-30 or skms-30(˜23)1||sks-50 or skms-50(˜45)1|
|1 Bound styrene content, percent|
|Tensile strength [meganewtons (MN) per sq m (kg-force/cm2)]...............||20(200)||23(230)||27(270)|
|Tear resistance (kN/m or kg-force/cm)...............||70||90||95|
|Rebound resilience (percent)...............||42||40||32|
|Wear resistance [cm3/(kW-hr)]...............||260||230||200|
|Brittleness temperature (°C)...............||-75||-52||-14|