ABSTRACT

This chapter reviews two commonly used rubbers, polybutadiene and neoprene. Polybutadiene is almost always used in blends with other rubbers, a major reason being the difficulty of mixing it alone. Neoprene, developed as a special-purpose rubber to give good resistance to petroleum hydrocarbons, remains a leading synthetic rubber despite competition from other synthetics. Although peroxide curing is possible, polybutadiene as an unsaturated rubber is usually vulcanized by conventional curing systems. Antioxidants are necessary in all neoprene compounds to ensure good aging. Neoprene compounds used in outdoor exposures are usually black or dark brown, since light-colored compounds darken in sunlight. To tackify neoprene compounds, coumarone indene resins and hydrogenated rosin esters are frequent choices. Good low temperature properties are achieved by using ester-type plasticizers like dioctyl sebacate. For retaining the flame-resistant properties in neoprene compounds, nonflammable phosphoric acid esters or chlorinated hydrocarbons can be used as replacements for mineral oils.