not more than 7 carbon atoms and R' is a monovalent organic radical having up to 20 carbon atoms, c) from 0.1 to 15% of a polymerizable polyvinyl crosslinking agent, d) from 0 to 2% of a polymerizable vinyl silane coupling agent, e) from 0.1 to 3.0% of a vinyl polymerization initiator. 10.