Research on the micro-structural evolution of phenol-formaldehyde resin modified by boron carbide

Phenol-formaldehyde (PF) resin usually could not be applied in the high-temperature environments due to its poor heat-resistance. Many kinds of modification methods had been presented in order to improve its stability of the structures and properties. In this paper, boron carbide (B(4)C) was used as the modification additives to improve the residue of PF resin after being treated at high-temperatures. Thermal gravity (TG) and scanning electron microscopy (SEM) were employed to investigate the residue and micro-structural evolution of modified PF resin during the heat-treatment process. TG results demonstrated that the residue of PF resin was improved effectively due to the satisfactory modification effects of B(4)C. SEM morphology showed that the distribution of B(4)C powders became propertional at the elevated temperatures, and boron oxides (13203) was formed in the interior of PF resin matrix. These results indicated that there existed complex modification reactions between B(4)C and volatiles released from the degradation of PF resin at high-temperatures. By means of the above modification reactions., some volatiles, especially for CO, converted into amorphous carbon and results in the increasing of residue after being treated at high-temperatures.