POSS改性EPDM耐烧蚀复合材料的制备及性能

Preparation and properties of POSS modified EPDM ablative composites

由于高性能推进剂的广泛应用,导致固体火箭发动机燃烧室内的燃烧温度与工作压强不断升高,因此研制出性能更加优异的隔热层迫在眉睫。以三元乙丙橡胶(EPDM)为基体,气相纳米SiO2为补强填料,首次引入八甲基丙烯酰氧基丙基POSS(MA-POSS),经由过氧化物引发双键之间的自由基聚合反应,制备了POSS改性EPDM耐烧蚀复合材料。研究了MA-POSS与气相纳米SiO2的添加量对隔热材料的交联度、力学性能、热稳定性、耐烧蚀性能的影响。在POSS与气相纳米SiO2协同作用下,改性后的材料各项性能均有所提升。结果表明,当气相纳米SiO2含量为40份、MA-POSS为5份时,凝胶含量高达92.61%,拉伸强度为12.02 MPa;MA-POSS含量为3份时,复合材料的线性烧蚀率和质量烧蚀率最低,分别为0.296 mm/s和0.100 g/s。

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.