Resin transfer molding system with controlled induction period for

Abstract

A method of forming synthetic articles of polyester resin by resin transfer molding techniques or the like comprising combining a set of reactants including a major base mass of polyester resin in fluid form, at least one polyester cure accelerator, a selected quantity of isocyanate, a surfactant and at least one promoter. The isocyanate is added in sufficient quantity to react with at least one other component in the mixture to produce quantities of carbon dioxide throughout the mixture. The resultant mixture is transferred into a closed mold prior to substantial reaction. The promoter is allowed to react exothermically with at least one other component of the mixture to trigger the isocyanate to react to evolve carbon dioxide gas to generate pressure to fill the mold. Thereafter a curing reaction between the cure accelerator and the polyester occurs to cure and solidify the expanded resin to produce an expanded article. Preferably reinforcement is placed within the mold prior to filling, the expansion of the mixture is effective to bring the fluid resin into pressured wetting contact with substantial regions of the surface of the reinforcement to incorporate the element within the resin by self working or gradual flow within the closed mold, and curing the expanded resin produces a reinforced expanded article.