HYPALON - HISTORICAL BACKGROUND

The development of HYPALON was the result of a long-term program at Du Pont that originated in the wartime need of the U. S. Government for new synthetic rubbers. This program was aimed at deriving a vuIcanizable rubber from polyethylene, partly because such a rubber might reasonably be expected to exhibit many of the chemical and electrical characteristics of polyethylene, and partly because it was recognized that polyethylene was likely to continue to be a low-cost starting material for the foreseeable future.

The initial outcome of the work was the discovery that a rubbery product could be obtained by chlorinating polyethylene in solution. Although this rubber was found to be vulcanizable with peroxides, the curing process was difficult because the vulcanizing peroxides now used in the rubber industry were not then available. To give a CPE-like elastomer with improved curing characteristics, Du Pont developed a modification of the solution chlorination process that permitted the simultaneous chlorination and chlorosulfonation of polyethylene. The product, chlorosulfonated polyethylene, was an elastomer, similar to CPE, but now readily curable with sulfur-containing curatives.

The two products, chlorinated polyethylene and chi oro sulfonated polyethylene, were both commercialized in 1951 as HYPALON S-l and HYPALON S-2, respectively. HYPALON S-l was soon withdrawn in favor of HYPALON S-225,26 which was subsequently renamed HYPALON 20. The latter is still commercially available and has proven to be the first of a family of chlorosul­fonated polyethylene synthetic rubbers.