Novel phosphorus-containing hyperbranched polysiloxane and its high performance flame retardant cyanate ester resins

A novel phosphorus-containing hyperbranched polysiloxane (P-HSi) with a great amount of phosphaphenanthrene and silanol groups was synthesized by a hydrolysis of self-made phosphorus-containing triethoxysilane. Based on this, P-HSi was used to develop a new high performance flame retardant cyanate ester (CE) resin with simultaneously improved integrated properties. A small addition of P-HSi (5 wt%) to CE can remarkably increases the flame retardancy of CE resin, where the content of P element is only as low as about 1.8 wt%. More attractively, the incorporation of P-HSi to CE resin significantly improves the thermal stability and mechanical properties, completely overcoming the disadvantages of phosphorus flame retardants. Specifically, for the modified CE resin with 15 wt% P-HSi, its initial degradation temperature is about 58 °C higher than the corresponding value of original CE resin; moreover, its impact and flexural strengths are about 2.7 and 1.5 times of the corresponding values of CE resin, respectively. In addition, the P-HSi/CE resins have obviously decreased curing temperature and improved dielectric properties. These outstanding integrated properties of P-HSi/CE resins show that P-HSi is an effective and multi-functional flame retardant for developing high performance resins.