Study On CF Reinforced Polysiloxane Based Ablative Composites

Based on the investigation on the data of preparation and modification of the polysiloxane ablative, the research on the CF — reinforced ablative with good properties prepared by polysiloxane as the matrix, CF as the reinforced material and the calcium carbonate as the inorganic filler was carried out.By the analysis of DSC, the property of the matrix polysiloxane was studied. The research compared SAR—2 with SAR—9 on the property of hear—resistance, oxidation—resistance and technical process. The research showed that it was not the major factor, which had bad impact on the overall performance of ablative composite, that SAR—9 had less residue and higher viscosity than SAR—2 had as the matrix. The inferior situation could be improved by treatments. With regard to the heat— resistance, solvent volume and technical property, SAR—9 has big advantage over SAR—2 and is suitable for the preparation of ablative material as the matrix. The research on the curing and improvement of the matrix showed that catalyst should be added into the matrix to ensure its complete curing and the toughening agent should be added into the matrix to give rise to the mechanical property of the composite. The research used the diethylen etriamine as the catalyst, the dibutyl(o-)phthalate as the toughening agent and the optimal dosage is 1%.By the analysis of mechanical and ablative properties and SEM, the improvement of the calcium carbonate and CF was studied. The research showed that the interface, ablation and mechanical property could be improved by the usage of DC—60 as the coupling agent for calcium carbonate and CF. With regard to the improvement for the interface of calcium carbonate, DC — 60 is better than tetrabutyl titanate. DC—60 could decrease the viscosity of the system to better the preparation while tetrabutyl titanate would increase the viscosity of the system. As far as the oil factor was concerned, DC—60 had better effect than tetrabutyl titanate, too. The treatment for CF was carried out by cleaning, liquid oxidation and polysilane coupling angent treatment sequently. Concentrated hydrogen nitrate was used in the liquid oxidation and the proper time for treatment is 2h. Excess time of treatment chould decrease the intensity of CF itself so as to decrease the performance of thewhole body. After the treatment of liquid oxidation, the volume of oxygenic group was increased to promote the polarity of the surface of CF. In this way, the impregnation and bonding between the fiber and the matrix was highly improved.The impact of the dosage of CF and calcium carbonate on the performance of composite is studied. The results showed that the use of calcium carbonate alone could decrease the ablation rate of calcium carbonate /SAR—9 composite while its mechanical property decrease. With the increase of the volume of CF alone, the mechanical property of composite decrease while its linear ablation rate and mass ablation rate decreased. The use of CF and calcium carbonate in the same time could greatly decrease the ablation rate of the material, which interests us the most. The optimal mixture ratio is CF: calcium carbonate: SAR—9=1: 15: 20, and in this situation, the mechanical property is desirable.