Abstract: Expandable ethylenically unsaturated polymer particles are produced by using in the process a suspension stabilizer comprising calcium carbonate particles having the surfaces thereof treated with resin acid. The method for the production of such expandable ethylenically unsaturated polymer particles from ethylenically unsaturated polymer particles includes suspending such particles in water and impregnating the particles with an organic expanding agent having a boiling point lower than the softening point of the polymer particles.

Abstract: A process for preparing expandable styrene polymer particles by using magnesium oxide as a suspending agent to prevent agglomeration of styrene polymer particles during impregnation with an expanding agent. The process comprises preparing expandable styrene polymer particles from styrene polymer particles in water, wherein the expanding agent (which does not dissolve styrene polymer particles or slightly swells the particles, and has a boiling point lower than the softening point of the particles) is added in the presence of the suspending agent and the particles being impregnated thereby.

Abstract: Expandable styrene polymer particle compositions containing (1) an expanding agent, which is volatilizable and does not dissolve or may slightly swell the styrene polymer particles, and having a boiling point lower than the softening point of the styrene polymer particles, and (2) a small amount of sulfur containing compound having the following general formula: ##EQU1## wherein R.sub.1 and R.sub.2 are the same or different higher alkyl groups having 12 - 18 carbon atoms and R.sub.3 and R.sub.4 are the same or different lower alkylene groups having 1 - 4 carbon atoms.