Abstract This work has confirmed that the thermal decomposition found to occur in a model alkanesulfonylchloride also occurs in an elastomeric CSM at the cure temperature. Therefore, less emphasis should be placed on the existence of ionic sulfonate salt bridges as the mode of crosslinking in cured chlorosulfonated polyethylenes. Though we have not presented any evidence to show that carbon-sulfur crosslinks arc involved in the cure, the need to incorporate sulfur-bearing accelerators in the formulation for practical cures suggests that activated sites adjacent to unsaturated double-bonds may be involved.