Thermoplastic particles are suspended in water or other suspending fluids with a suspending aid(s) to prevent agglomeration of the beads, pellets or particles. To this suspension is added monomer(s) containing a multifunctional initiator(s). The monomer and initiator(s) are preemulsified in water or other fluid(s) before the addition in order to improve distribution of the monomer(s) and initiator(s) in or on the particles. After or during the addition(s), the suspension temperature is raised to cause polymerization. The procedures may be repeated to increase the coating or penetrated polymer content. New compositions of matter are made by this technique wherein the new compositions are plastic resins either coated or penetrated, or both, with a thermoplastic(s) of very high molecular weight not obtainable by present, commercial polymerization techniques. The compositions are superior to the feed resins because of the enhancement of physical properties brought about by the high molecular weights phase(s). This enhancement would be extended to foams made from these new resins.