Foaming agent with alcohol activator and method for producing non-chalking polymers

摘要

A method of making a foamed polymer article by injection molding, using a foaming agent that evolves minimal water and does not form byproducts which could pit or chalk the polymer surface. The foaming agent contains sodium borohydride in an amount from 0.01 weight percent of the polymer to be foamed, and a polyhydric alcohol such as six-carbon mannitol as an activator to react with the sodium borohydride and produce hydrogen gas. Boric acid can be included with the alcohol. The sodium borohydride is kept separated from the other reactive components such as by encapsulation until gas production is desired when the polymer is heated and molded.