The present invention provides compositions such as a polymer grout, a molded plastic part, a void-filling plastic material, a concrete-anchoring material and a polymeric casting made from a thermosetting polymer chosen from vulcanized rubbers, polyoxybenzylmethylen-glycolanhydride ("Bakelite"), novolac resins, resole phenolic resins, duroplast, bismaleimide resins, polyimide resins, melamine, acrylic resins, polyester resins, cyanate ester resins, phenolic triazine resins, paracyclophane resins and epoxy resins and at least one phase change material ("PCM"). The compositions of the present invention have a lowered exotherm compared to compositions made from the same thermosetting polymer without the addition of a phase change material. Also provided are improved processes for producing the inventive compositions.