Preparation of a novel synergistic flame retardant and its application in silicone rubber composites

Dehydration condensation product (DHCP) was prepared by addition and dehydration condensation reactions of 9,10-dihydro-9-oxa-10-phenanthrene-10-oxide (DOPO), vinyl trimethoxysilane, and (3-aminopropyl) triethoxysilane. DHCP-PA with high phosphorus content was prepared by reaction between DHCP and phytic acid (PA). It was then compounded with oxidized multi-walled carbon nanotubes (OMWCNTs) to prepare silicone rubber (SR) flame retardant composites. The results showed that the SR with a small amount of DHCP-PA owned good flame retardant effect. The heat release rate (HRR) was decreased from 436 kW/m(2)for pure SR to 288 kW/m(2)for the SR with 5 phr DHCP-PA, and the decreasing degree was 33.9%. After mixing 5 phr DHCP-PA with 1 phr OMWCNTs, the HRR of SR composite was decreased from 436 to 251 kW/m(2), the smoke production rate was decreased from 0.161 to 0.087 m(2)/s, the limited oxygen index value was increased from 20.4% to 28.4%, and the flame retardant grade can reach UL94 V-0. In addition, the synergistic flame retardant mechanism was researched and analyzed.