POSS改性EPDM耐烧蚀复合材料的制备及性能

The high demands of nanocomposite rocket ablative materials for thermal protection system in space vehicles applications has resulted in extensive developments in cost-effective heat-shielding materials. Wide applications of high-performance propellants leads to rising temperature and working pressure in solid rocket motor combustion chambers, which have paved the way for the enhancement of ablative heat-shielding materials. Here the properties of heat-shielding nanocomposites, based on ethylene propylene diene monomer(EPDM)copolymer additionally modified with fumed nano-silica and functional octa-methacryloyloxypropyl polyhedral oligomeric silsesquioxane(MA-POSS), were examined. Cross-linking percentages with respect to gel contents have been achieved with a certain method of refluxing toluene in a soxhlet extractor. The mechanical properties were characterized by tensile strengths and elongations at break. Thermal stability was demonstrated from TG analysis in the temperature range up to 800℃ from room temperature. The ablation characteristics in terms of liner ablation rates and mass ablation rates were investigated by using an oxyacetylene flame torch equipment in accordance with national standard GJB323A-96, which simulates the conditions of solid rocket motor combustion chambers. The surface topographies of ablated samples were observed by means of SEM. The results shows that maximum gel content of 92.61% and tensile strength of 12.02 MPa are achieved for EPDM with 40 phr of SiO₂ and 5 phr of MA-POSS. The lowest linear and mass ablation rates are as low as 0.296 mm/s and 0.100 g/s respectively by using 3 phr of POSS.