Vinyl monomer compositions with accelerated surface cure

A vinyl monomer composition exhibiting improved cure in an oxygen-containing environment comprising (1) a de-inhibiting amount of from about 5% to about 15% weight percent of diolefin rubber dispersed in monomer comprising isobornyl methacrylate having a partial pressure less than about 1 millimeter of mercury at 50.degree. C., (2) a multifunctional monomer selected from the group consisting of diacrylates, triacrylates, dimethacrylates, and (3) a catalyst consisting of at least one polyvalent cobalt salt, wherein (a) said diolefin rubber is polymerized in at least two stages including an initial stage and a subsequent stage, said initial stage comprising polymerizing a diolefin monomer selected from the group consisting of 1,3-butadiene, 2-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-cyano-1,3-butadiene, 1,2,3,4-tetrachlorobutadiene, isoprene, 1,4-hexadiene and dicyclopentadiene, and said subsequent stage comprising polymerizing a monomer selected from the group consisting of styrene, methyl methacrylate and (C.sub.2 -C.sub.8) alkyl acrylate, and (b) said diolefin rubber is insoluble in said vinyl monomer composition.