Abstract: A complex is formed by the reaction of an aluminum salt such as aluminum sulfate with a high molecular weight (for example, above 60,000 M.W.) collagen. Collagen-aluminum complex is dispersed in water and serves as suspension agent for suspending polystyrene beads during impregnation of a blowing agent, even when the concentration of the suspending agent is of the magnitude of 0.05% by weight of the beads. The aqueous system is drained from impregnated expandable beads, which are washed, but which retain adherent deposits of said collagen-aluminum complex in measurable amounts. The dried coated beads have minimized propensity toward lumping when pre-expanded. The prepuffed particles can pass tests concerned with resistance toward static electrical phenonomen better than corresponding prepuffed particles lacking such deposit of collagen-aluminum complex.