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

Summary 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.