Enhanced thermal and anti-ablation properties of high-temperature resistant reactive POSS modified boron phenolic resin

To further improve the anti-ablation property of boron phenolic resin (BPR), high-temperature resistant reactive trisilanolheptaphenyl POSS (3OH-POSS) was synthesized to modify BPR. The thermal stability of BPR was significantly improved. The initial decomposition temperature of the prepared 3OH-POSS modified BPR (POSSBPR) was increased from 226.0 to 390.2°C and the chars at 800 and 1000°C was increased from 71.1 and 66.7% to 75.1 and 73.7%, respectively with 20% 3OH-POSS addition. The prepared POSSBPR castings obtained linear ablation rate (LAR) and mass ablation rate (MAR) were as low as −0.122 mm/s and 0.0465 g/s. And the LAR and MAR of high silica fiber reinforced composites (HSC/POSSBPR) were 0.123 mm/s and 0.0602 g/s, respectively. Moreover, the mechanism of high-temperature carbon microcrystalline and ceramic structure transformation, and ablation performance enhancement of POSSBPR were determined by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. Results indicated that the introduction of 3OH-POSS promotes the formation of ordered graphite structure of BPR and forms high-temperature species, such as SiC ceramic, on the ablated surface, which subsequently improves the ablation resistance of the material.