Examples of such monomers would be vinyl aromatic monomers such as styrene and alpha-methylstyrene; nitrites such as acrylonitrile; vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride; vinyl esters such as vinyl acetate and vinyl propionate and alkyl acrylates or methacrylates containing from 1 to 4 carbon atoms in the alkyl group such as methylmethacrylate, butyl acrylate