Mixtures of reactive thermosetting resins which are stable at ambient temperature, latent catalyst complexes for hardening said mixtures, processes for their manufacture, and heat-hardened resins obtained from said mixtures. Mixtures of heat-reactive thermosetting resins which are stable at ambient temperature for use in impregnating insulation for electrical materials or in the preparation of molding products or composite materials, comprising liquid oligo- or poly-isocyanate compounds and liquid epoxy resins and a latent hardening catalyst which is inert at ambient temperature and is composed of an addition complex of an amine compound from the group consisting of the amines, the alkylhydrazines and the imidazoles, and a boron halide. They additionally comprise a small quantity of maleic anhydride or the boron halide is boron tribromide with no addition of maleic anhydride. Latent catalyst complexes of these mixtures, formed by the addition complexes of BBr.sub.3 and an amine, an alkylhydrazine or an imidazole. Their manufacturing processes and the resins obtained from said mixtures.

Polyurea polymers prepared from formulations including a polyisocyanate, a polyamine and a polyepoxide can have good heat stability and good physical properties in the substantial absence of uretidine diones and isocyanurates. The polymers can be prepared in one step of admixing and heating at greater than 150.degree. C. or in a two step process by first admixing the components at less than 130.degree. C. and then postcuring the product at greater than 150.degree. C. The polyurea polymer, after postcuring, can have substantially no residual epoxy or oxazolidinone groups. These polymers were particularly useful for applications which require the exposure of the polyurea polymers to both intermittent high temperatures and high humidity. The polyurea polymers of the present invention can withstand higher temperatures than conventional polyurea polymers without blistering.