PURPOSE: To obtain a water-crosslinkable polyolefin improved in properties such as flexibility, stress cracking resistance, impact resistance and adhesiveness without detriment to extrudability and being quickly crosslinked in the presence of water.

CONSTITUTION: This copolymer composition comprises 100 pts.wt. silane/olefin copolymer prepared by copolymerizing ethylene with an ethylenically unsaturated silane compound, 1-24 pts.wt. silanegrafted polyolefin, and 0.001-10 pts.wt. silanol condensation catalyst.