Poly(dimethyl-diphenyl-imide)siloxane/phenolic-based double network hybrid resin coatings for ablation thermal protection

Organic-inorganic hybridization is an important way to improve ablation resistance of phenolic resin coatings (PR). However, long molecular chain silicone by copolymerization is less compatible with PR and hybrid resin will form sea-island phase, which is not favorable for further improvement of ablation resistance. Therefore, how to achieve a combination of long chain and compatibility is a major challenge. In this work, the poly(dimethyl-diphenyl-imide)siloxane (PMPI) containing imide and phenyl was synthesized by anionic ring-opening polymerization and copolymerization. Then, it was hybridized with PR to obtain PMPI/PR-based double network hybrid resin coatings with nano co-continuous phase. The oxyacetylene ablation test suggests that the resin coatings with medium phenyl content has the lowest linear ablation rate (0.055 mm/s), which is 74 % lower compared to PR (0.21 mm/s). In addition, the mechanism by which PMPI enhances ablation resistance is discussed. This work provides a promising approach to develop higher performance ablative-resistant resin coatings.