In situ construction of fiber-supported micro-porous char structure to enhance anti-ablative performance of silicone rubber composites

Ablation-resistant polymeric composites play a crucial role in the thermal protection system for the entire aerospace industry. Constructing a stable char layer especially with low thermal conductivity is essential to enhance the ablation resistant properties of polymer-based ablatives. In this article, basic magnesium carbonate (MgCO 3 ) and carbon fibers (CFs) were introduced to silicone rubber with an aim of building fiber-supported micro-porous char structure in situ, thereby improving ablation resistance properties. Thermogravimetric analyses revealed that the addition of MgCO 3 significantly increased the char residue of the composites. Oxyacetylene torch tests indicated that the addition of MgCO 3 /CFs greatly improved the thermal insulation of the composites, and the linear ablation rates of the composites were reduced by 30.76% compared to the virgin silicone rubber. Shore A hardness and thermal conductivity tests revealed that composites with 10 phr MgCO 3 exhibited a char structure with proper strength and low thermal conductivity. SiC, Mg 2 SiO 4 , and MgSiO 3 were produced in the MgCO 3 /CFs-modified composites, as characterized by X-ray diffraction. Combined with macro lens and scanning electron misroscopy, it was proven that a fiber-supported micro-porous and thermally insulated char structure was conducive to the improvement of the ablation properties, which can be applied to aerospace systems for thermal shielding applications.