Thermoset polyurea resins with in situ produced silicate filler from water glass: effects of water dispersible alumina nanoparticles

Abstract

Proprietary polyurea based thermosets (3P resins) were produced from polymeric methylene diphenylisocyanate (PMDI) and water glass (WG) using a phosphate emulsifier. Water glass was dispersed in the PMDI and phosphate resulting in a water in oil (W/O) type emulsion. Water dispersible alumina of various nominal particle sizes (25 to 220 nm) were added in the WG in various amounts (1 and 5 wt-%) in absence and presence of an antifoaming agent in order to study their effects on the resulting cross-linked polyurea based systems. The latter contained microscaled polysilicate particles derived from the WG. The flexural stiffness, fracture toughness and energy of the related thermosets were slightly improved. On the other hand, the flexural strength and strain were reduced by incorporation of the aluminas. The results suggested that the alumina affected mostly the reaction pathways between WG and PMDI owing to their preferential location at the surface of the WG particles in the initial W (WG)/O (PMDI z phosphate) emulsion.