Study on the Structure and Properties of a Hybrid Resins

Abstract

Polysilicate modified polyurea/vinyl ester hybrid resins were produced by dispersing water glass (WG) in a mixture ofvinyl ester (VE) and polyisocyanate in presence of a liquid phosphate as emulsifier. As styrene-crosslinkable VE resinsbisphenol A (BA) and novolac types (N), whereas as polyisocyanate a polymeric methylene diphenyl isocyanate (PMDI)were used. The structure and selected properties of the hybrid resins were determined and compared to those of the neatVEs and polysilicate filled polyurea (denoted as 3P resin). Using VE for resin hybridization, which worked as anadditional emulsifier for the WG/PMDI/phosphate system, resulted in a fine particle dispersion of the polysilicate. Itwas found that the type of VE affected not only the dispersion of WG (and thus of the polysilicate) but also the networkformation of the polyurea/VE hybrids and their properties. Information about the structure of the polysilicate filledhybrid resins was gained from dynamic-mechanical thermal analysis (DMTA), scanning electron and atomic forcemicroscopic measurements. It was argued that the resin hybridization yielded a conetwork instead of an interpenetratingone. The properties of the hybrid systems were determined by DMTA, fracture mechanical tests, thermogravimetricanalysis and flammability measurements. It was established that the stiffness and resistance to thermal degradation ofthe initial 3P resin was strongly improved by hybridization with VEs. The fracture toughness (Kc) proved to be lesssensitive to the formulation of the hybrid resins. On the other hand, the fracture energy (Gc) and limiting oxygen indexexperienced a positive deviation from the additivity as a function of the 3P/VE composition, at least in a given range.