Abstract: Phenolic resin-based nanoporous material (PNM) is a new kind of light-weight and efficient thermal protection material that meets the demand of new-generation aerospace craft. Traditionally, its fabrication requires supercritical drying technique which is costly and time-consuming. In this work, PNM is fabricated via a two-step approach including the synthesis of novolac resin and the sol-gel process, making the ambient pressure drying of PNM possible. The effects of curing agent amount, curing temperature, and curing time on the structure were systematically investigated. And the factors affecting shrinkage and thermal stability were also identified. The results show that the change of nanoporous structure of PNM can affect the shrinkage of PNM after drying. Larger particles and larger pores contribute to smaller shrinkage. The thermal stability of PNM is mainly influenced by its chemical composition and molecular structure. Higher thermal stability is expected when the addition of curing agent was optimized. When the curing agent amount is 10%, the curing temperature is elevated to 150℃, and the curing time is extended to 48 h, the obtained PNM has the highest thermal stability (char yield of 54.2% at 900℃), highly developed nanoporous structure (surface area of 264.0 m²/g, pore volume of 2.67 cm³/g and average pore diameter of 40.0 nm), and the smallest shrinkage after drying (0%). This kind of PNM is promising to be used in future aerospace crafts for its easy fabrication and excellent performance.

Key words: phenolic resin, nanoporous material, thermal protection, ambient pressure drying, structure control