Enhanced thermal stabilities and char yields of carbon fibers reinforced boron containing novolac phenolic resins composites

4-hydroxymethyl phenylboronic acid (4-HMPBA), phenol and formaldehyde were for the first time to synthesize boron containing novolac phenolic resins (Novolac-4-HMPBA). Its corresponding carbon fibers (CF) composites were also fabricated via the lamination followed by hot-compression. Results revealed that Novolac-4-HMPBA was successfully synthesized. Compared to common novolac phenolic resin (NPR), the corresponding decomposition temperature of 5% weight loss (T₅) and char yield at 800 °C (C₈₀₀) of cured Novolac-4-HMPBA-30 were increased to 369.1 °C and 69.7%, increased by 41.3% and 26.3%, respectively. The CF/Novolac-4-HMPBA-20 composites presented relatively higher interlaminar shear strength (ILSS) of 35.9 MPa, increased by 50.2% compared to that of CF/NPR composites. After the treatment at 800 °C for one hour under Ar atmosphere, the corresponding ILSS value of CF/Novolac-4-HMPBA-20 composite was decreased to 7.8 MPa, but still higher than that of CF/NPR composites (3.0 MPa).