It should be noted that when I refer to a vinyl lower alkoxysilane I mean a compound having the following formula: wherein R is an organic group, R1 is an organic group containing at least one vinyl functional group, R2 is lower alkyl, m is 0, 1 or 2, n is 1 to 3, p is 1 to 3 and the sum of m, n and p is 4.