Melamine-formaldehyde resin (MF) was selected as potential reactive emulsifier for polyurea-based thermoset resins produced from polyisocyanate/water glass (WG)/emulsifier systems. As emulsifier tricresylphosphate and/or MF served for the initial water-in-oil type ("water" WG; "oil" polyisocyanate + emulsifier) emulsions. The MF content of the systems has been varied (<= 15 wt %) and its effect on the structure, mechanical, thermal and flammability properties of the final polyurea-based thermosets studied. It was found that MF is a suitable emulsifier, which can fully replace the phosphate without negatively affecting the properties of the resulting hybrid thermosets. Moreover, hybridization with MF was often accompanied with pronounced improvements in fracture mechanical and static flexural properties. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 7-14, 2011