EPDM-Gummidichtungen für hydraulische Zylinder.

摘要

The invention relates to EPDM rubber seals for use in hydraulic cylinders such as the cylinders of automotive brake and clutch systems. Using an EPDM rubber compositon carefully formulated so as to be good in kneadability, rubber seals having good resistance to yielding or loss of resiliency by fatigue as well as sufficient strength and elongation are obtained. Essential components of the rubber composition are 100 parts by weight of EPDM copolymer rubber, 30-80 parts by weight of carbon black and 1-5 parts by weight of a peroxide as cross-linking agent. It is important to use an EPDM copolymer in which the distribution of ethylene is uneven such that the content of ethylene is highest in a fraction highest in molecular weight and is lowest in another fraction lowest in molecular weight. The difference in ethylene content between these two fractions of the copolyer should be more than 5 wt% and not more than 9 wt%.