A Novel Acetylene-Functional/Silicon-Containing Benzoxazine Resin: Preparation, Curing Kinetics and Thermal Properties

Benzoxazine resin has been paid more attention in the fields of aviation, electronics, automobiles and new energy industries because of its excellent comprehensive performance. Further application is limited, however, by shortcomings such as high brittleness and high curing temperature. Furthermore, higher thermal stability is imperiously demanded in special areas. Incorporating both an acetylene group and silicon into the benzoxazine monomer is a promising possible solution to improve the curing processability, thermal properties and toughness of benzoxazine. In this paper, an acetylene-functional/silicon-containing benzoxazine monomer was prepared by two-step synthesis, and acetylene-functional benzoxazine was also prepared as a comparison. FTIR and ¹H NMR confirmed the molecular structure of acetylene-functional/silicon-containing benzoxazine. Differential scanning calorimetry (DSC) analysis showed that the initial and peak degradation temperatures of acetylene-functional/silicon-containing benzoxazine were decreased by 21 °C and 18 °C compared with acetylene-functional benzoxazine, respectively. The apparent activation energy of the curing reaction of acetylene-functional/silicon-containing benzoxazine was 83.1 kJ/mol, which was slightly lower than acetylene-functional benzoxazine (84.7 kJ/mol). TGA results showed that the acetylene-functional/silicon-containing benzoxazine had a higher thermal stability than acetylene-functional benzoxazine. The temperatures of 5% weight loss of acetylene-functional/silicon-containing benzoxazine were 380 °C in nitrogen and 485 °C in air, and the char yield at 1000 °C was 80% in nitrogen and 21% in air, respectively. The results of mechanical properties showed that the impact strength of acetylene-functional/silicon-containing benzoxazine was higher than acetylene-functional benzoxazine by 35.4%. The tensile and flexural strengths of acetylene-functional/silicon-containing benzoxazine were slightly higher than that of acetylene-functional benzoxazine.