Ultra low-temperature fabrication of hollow glass microspheres and polysilazane coating for enhanced thermal protection of carbon/epoxy composites

This investigation was aimed to develop high-temperature resistant coatings suitable for carbon fiber-reinforced epoxy composites at ultra low preparation temperatures. In the organic-inorganic coating, hollow glass microspheres were chosen as the filling phase, and polysilazane was selected as the film-forming material. Fourier transforms infrared spectra showed that polysilazane can be cross-linked and solidified at low temperatures, which provided the possibility for protecting the substrate from high-temperature damage. By modifying the surface of hollow glass microspheres, the coating dispersions were able to maintain good stability within 120 min. The coating exhibited good thermal vibration resistance and could stand at 220 °C for 30 min after 6 cycles without obvious cracking and peeling. After the static thermal test, the coated composites still maintained a flexural strength of 603.7±19.2 MPa (retention rate can reach 86.6%) at 250 °C, which was higher than that (593.3±14.8 MPa) of uncoated samples at 190 °C. The results indicated that the coating has the advantage of low curing temperature, convenient operation, and excellent thermal protection performance, which could further expand the potential application of carbon fiber-reinforced epoxy composites in firefighting unmanned aerial vehicles, hypersonic missiles, and other fields.