Effects of phosphate and polysiloxane on flame retardancy and impact toughening behavior of poly(2,6-dimethyl-1,4-phenylene oxide).

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based compounds containing resorcinol bis(diphenyl phosphate) (RDP) and poly(dimethyl-diphenyl siloxane) (PDMDPS) were prepared through melt extrusion, and their flammability characteristics and mechanical properties were evaluated. The incorporation of RDP enhanced the flame retardancy of PPO compounds, but hardly made them obtain the UL 94 V-0 rating unless RDP and PDMDPS were combined. Studies on the residual chars after vertical burning test suggested that the excellent flame retardancy be correlated with the retention from the combination effects of silica and phosphate in the char, whose cross-linked silica enhanced the formation of a compact char to retard combustion. Thermogravimetric analysis indicated that the presence of PDMDPS and RDP improved the char yielding as well as the decomposition temperature of PPO compounds. Moreover, the Izod impact strength was improved significantly in the presence of RDP and PDMDPS, and this toughening effect was attributed to the deformation and multiple cracks induced by PDMDPS, which enhances the impact energy absorption of the matrix. This work provides a very effective flame retarding formulation for PPO compounds with improved impact toughness. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]