Hybrid resins from polyisocyanate, epoxy resin and water glass: chemistry, structure and properties

Epoxy resin (EP) was selected as potential reactive emulsifier for polyurea-based thermoset resins produced from polyisocyanate/water glass/emulsifier systems. As emulsifier diphenyl-2-ethylhexylphosphate and/or EP served for the initial water-in-oil type emulsions whereby “water” means water glass, and “oil” the organic phase, composed of polyisocyanate and emulsifier, respectively. The EP content of the systems has been varied from 15 to 35 wt% and from 35 to 45 wt% for the hybrid resins with and without DPO emulsifier, respectively. Effects of EP hybridization on the structure, mechanical, thermal and flammability properties of the final polyurea-based systems were studied. EP proved to be a suitable emulsifier based on the fact that the mean size of the polysilicate, generated from the dispersed WG, was markedly reduced. EP could even fully replace the phosphate emulsifier without sacrificing the mechanical properties of the resulting hybrid thermosets. Moreover, the hybridization with EP was accompanied with improved stiffness and fracture toughness.