Preferred multifunctional acrylates are those of the formula: ##STR2## where each R4 is independently selected from the group consisting of a hydrogen atom and an alkyl group of 1 to 2 carbon atoms, each R5 is independently selected from the group consisting of an alkyl group of 1 to 6 carbon atoms and a radical of the formula: ##STR3## in which R6 is a hydrogen atom or an alkyl group of 1 to 2 ca