Full definition
Chlorosulfonated polyethylene — a specialty synthetic rubber originally developed by DuPont (Hypalon trademark, now discontinued brand but the generic CSM polymer remains available). Provides an excellent combination of weather resistance, ozone resistance, chemical resistance (acids, alkalis, oxidizing chemicals), abrasion resistance, and color stability (can be produced in bright colors without fading). Temperature range: -30 to +120°C continuous. Properties: hardness 40-90 Shore A, tensile 10-20 MPa, elongation 200-500%, good electrical insulation. Limitations: poor resistance to aromatic and chlorinated solvents, moderate compression set. ASTM D2000: BE/CE. Applications: roofing membranes (white reflective, 20+ year life), cable jacketing, chemical tank linings, industrial hose, inflatable structures, and coated fabrics. CSM is often used where EPDM would work but color stability or better chemical resistance is needed. Now manufactured by Tosoh (Exoprene), DuPont exited the market. Declining usage as EPDM and FKM cover most applications.