Polychloroprene contains about 40% chlorine in a thermally stable backbone structure. It has a long history of use for applications requiring flame retardancy, such as conveyor belts, mass transit vehicle interiors, electrical insulation and jackets. A book was published by DuPont in 1963 on Neoprene. Typically, the formulation will contain 5-15 phr antimony trioxide, 5-15 phr zinc borate and 15-40 phr ATH. Where a soft formulation is desired, a lower molecular weight Neoprene can be included, and chlorinated paraffins and/or phosphate ester plasticizers can be included.
Although polyolefins and elastomers pose more of a challenge to flame retardancy because of their high heat of combustion and poor char formation, a wide variety of effective flame retardant systems are available. The challenge to the compounder is to meet flame retardancy requirements with acceptable retention of useful properties and at acceptable cost. The application of a system approach (optimizing combinations of a additives) and the use of synergism appear to offer useful solutions. Statistical design of multivariate experiments seems advisable, using designs which uncover interactions.