Isocyanate-based polymer foam and process for production thereof

An isocyanate-based polymer foam comprising an isocyanate-based polymer foam matrix having disposed therein a particulate material having an enthalpy of endothermic phase transition of at least about 50 J/g. A process for producing the foam is also described. During the process, the particulate material acts as a heat sink and will undergo an endothermic phase change by absorbing a significant portion of the heat of reaction liberated during the process. This improves the safety of the process by lowering the maximum exotherm experienced by the foam and/or improves product properties.