Abstract: A lightweight open celled foam, having a density no greater than 6 pounds per cubic foot (pcf) and a ratio of imide to amide groups greater than 1 to 1 and no greater than 19 to 1, is the reaction product made from an organic polyisocyanate having at least two functional groups per molecule and a mixture of a difunctional acid and a difunctional anhydride in the presence of a tertiary amine catalyst and a nonionic, organic surfactant having a hydrophilic/lipophilic balance (HLB) of at least 12, with the reactants generating carbon dioxide during the manufacturing process.