Study On Formulation And Properties Of Silicone Rubber Insulation Materials

In this paper, aiming to get a high-quality RTV silicone rubber insulation materials, basic foruma and preparation process of the ablator was optimized,meanwhile, the effects of the major components, including ceramic fillers,ablation fillers and novel flame retardants, of the ablator on the mechanical, ablation and flame ratardancy properties were studied systematically.Firstly, the RTV silicone rubber insulation materials formulation was optimized based on the existing formula. Effects of the content of, on the mechanical and ablation properties were studied; The results show that the formulation with 50%phenyl silicone rubber, 20% gas phase-SiO2 and 8% aramid short fiber is optimal.Secondly, ceramifying silicone rubber insulation material was prepared by blending RTV-107 matrix, low softening point glass frits and silicate minerals:mica,wollastonite and calcined kaolin. The results show that silicate minerals can improve thermal stability of silicon rubber,enhance their microstructures and increase ultimate strength of ceramic residues on the basis of ensuring the mechanical properties. SEM observation reveals that the morphology of carbon residues are loosely masses and porous structure linked by liquid phase bridge after pyrolysed at 600 and 800-1000℃respectively. In particular, the sample adding kaolin is the optimal of comprehensive performance, the linear and mass ablation rates reached to the lowest 0.218mm/s and0.107g/s, which played a crucial role in heat insulation and erosion resistant.Phosphorus-based flame retardants—ammonium polyphosphate(APP),aluminum diethylphosphinate(ADP) and octaphenyl polyhedral oligomeric silsesquioxane(OPS)—were incorporated into room temperature vulcanized(RTV)silicone rubber insulating composites, in order to study the influence on the ablative and flame-retardation properties of the RTV silicone rubber composites. The results showed that the FRs remarkably improved the ablative and flame-retardation properties of the RTV silicone rubber composites. Furthermore, APP or ADP combined with OPS exhibit a significant synergistic effect in improving the overall performance of RTV silicone rubber composite. Specifically, the linear ablation rate(0.079 mm/s) was reduced by 45.9% with 15 wt. % ADP and 10 wt. % OPS in theRTV silicone rubber composite.Lastly, application of cyclotriphosphazene derivative in flame retardant RTV silicone rubber composite was studied. A novel non-halogen flame retardant,N3P3[NH(CH2)3Si(OCH2CH3)3]6, named as APESP were synthesized according previous research. The results show that APESP remarkably improved the ablative,thermal stability and flame-retardation properties of the RTV silicone rubber composites when used as cross-linker in RTV silicone rubber.