Preparation and properties of precursor of phenolic-based carbon foams

Hollow phenolic microspheres were incorporated into thermoset phenolic resin to synthesize phenolic foams precursor with closed-pore structure by mold forming and high temperature curing. Microstructure, mechanical properties, high-temperature resistance and heat-insulating properties were characterized by SEM, universal testing machine, thermogravimetric analyzer and themal physical properties measurement meter respectively. The results show that a large amount of closed micro-pores are distributed uniformly throughout the phenolic foam, compressive fracture characteristics of which was pseudoplastic. With adding proper content of microspheres, the fracture toughness and specific compressive strength could be improved obviously. The phenolic foam possesses good thermal stability. Its initial thermal-decomposition temperature is 210°C. The char yield is 51.9% at 750°C. The phenolic foam also exhibits good heat insulation for its low thermal conductivity, which is 0.057 W/(m·K) at 100°C with 45% of microspheres, lower than that of pure phenolic resin by as much as 47%.