PURPOSE: To obtain a material excellent in vibration-damping properties, flexibility, etc., in a medium-to high-temperature region by mixing a mixture comprising a specified copolymer and a specified elastomer with a tackifier, mica and a specified flame retardant.

CONSTITUTION: The material comprises 100 pts.wt. mixture comprising a polyisobutylene/polybutene-1 copolymer (A) and an elastomer (B) comprising styrene, polyisobutylene and polybutene-1 in an A to B weight ratio of desirably 80/20-30/70, 15-45 pts.wt. tackifier (e.g. petroleum resin), 50-200 pts.wt. mica as a filler and 50-200 pts.wt. at least a metal hydroxide or a salt of phoiprohic acid [e.g. Mg(OH)2 and calcium phosphete ]. The figure shows the complex loss factor vs. temperature relationships.