| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject composition, capable of maintaining excellent processability, expandable at a high expansion ratio, having a high rigidity and excellent in compression set and shape retaining properties by including ethylene-propylene-5-ethylidene-2-norbnornene copolymer rubbers (hereinafter abbreviated to ENB-based EPDMs) as a rubber component therein. SOLUTION: This composition is obtained by including (A) a low-molecular weight ENB-based EPDM having 25-35 Money viscosity (ML1+4 100 deg.C) and <=3 value of Q (Mw /Mn ), (B) a high-molecular weight ENB-based EPDM having 100-150 Mooney viscosity and 7-8 value of Q, (C) a sulfur vulcanization-based agent consisting essentially of sulfur and a zinc carbamate-based and a sulfenamide-based vulcanization accelerators and (D) an expansion-based agent consisting essentially of N,N'-dinitrosopentamethylenetetramine and urea at (40/60) to (20/80) weight ratio of the components A/B and has 3.5-5.0 pts.wt. content of the component C based on 100 pts.wt. total amount of the components A and B and 4.0-6.0 pts.wt. content of the component D based on 100 pts.wt. total amount of the components A and B. |
