Abstract: Compositions are provided which consist of a solid suspension of:a. a prepolymer obtained by reacting a N,N'-bis-imide of an unsaturated dicarboxylic acid of general formula: ##STR1## in which D represents a divalent organic radical containing a carbon-carbon double bond and A represents a divalent organic radical possessing from 2 to 30 carbon atoms, and a polyamine of general formula:R (NH.sub.2).sub.xin which x represents an integer at least equal to 2 and R represents an organic radial of valency x, the bis-imide being used in an amount from 0.55 to 25 mols per mol of --NH.sub.2 group introduced by the polyamine, suspended in:B. water, and optionally,C. a polar water-miscible organic solvent having a boiling point between 110.degree. C and 270.degree. C in an amount up to 50% by weight of the liquid phase. These compositions are thixotropic and useful for coating and impregnating fibrous materials and the like from which valuable resinous composites can be obtained.