For the purpose of receiving compositions of higher thermal and chemical firmness SKEP-50 and SKEPT-60 copolymers are modified by the chlorinated and sulpho-chlorinated atactic propylene – HAPP, SHAPP in a laboratory rubber-mixer during 8–10 minutes, at 20–40⁰С. It is shown that the high ratios of physical-mechanical properties are reached at vulcanizates, which vulcanized at 150ºС, within 30 and 40 minutes. As a result of modification, along with the main indicators of physical-mechanical properties of SKEP-50 and SKEPT-60, the hardness indicators are improved at breaking of the thermal and chemical resistance and adhesive durability.