disclosed is a closed - cell polyisocyanurate foam composition capable of high compressive strength at temperatures up to 200 ° c . the new composition further exhibits no loss or degradation in conventional mechanical properties — less than that which impacts the intended use . the formulation of the present invention is based on the reaction product of a isocyanate and an epoxide resin catalyzed by a mixture of a tertiary amine and a cyclic amine . compressive strength is augmented by incorporating a large fraction of a non - reactive bulk filler into the precursor polymer gel .