Аннотация:Research works on the creation of urethane-forming compositions suitable for their use as bindersin the preparation of composites by vacuum infusion are initiated. The characteristic features of the occurrenceof curing processes during the urethane formation reaction which are accompanied by the appearanceof a stable heterogeneous system are found. The character of interaction of the individual components of thepolyurethane binder is determined by laser microinterferometry. Assumptions about the factors promotingthe formation of a biphasic system are made based on the performed experiments. Ways to eliminate undesirableheterogeneity in reaction mixtures are proposed.