The Performance and Synthesis of Alkynyl-Functionalized Benzoxazine Containing Phthalide Side Groups and Cyano Groups with Different Molecular Weights.

Benzoxazine resins are widely employed in a variety of applications due to their exceptional heat resistance and treatment properties. However, traditional benzoxazine resins still confront hurdles in today's engineering applications, such as their inability to provide long-term service in high-temperature settings and their inadequate toughness. In this study, four alkyne-functionalized benzoxazines with phthalide side groups and cyano groups of varying molecular weights were produced. Fourier transform infrared spectroscopy (FT-IR) and hydrogen nuclear magnetic resonance spectroscopy (H-NMR) were used to characterize the resin structure, and differential scanning calorimetry (DSC) was used to investigate the thermal curing kinetics at different warming rates. The apparent activation energy was 116.9 kJ/mol. In-situ FT-IR was used to investigate the cure mechanism. Dynamic mechanical analysis (DMA) was used to evaluate the gelation time of BOZ series resins at various temperatures, and the curing process was designed by combining the results with DSC. The Tg of the composites made using BOZ-1N21 as the matrix was 336 °C, which was much higher than the Tg of the BP-a resin made with aniline, phenolphthalein, and formaldehyde (Tg = 251 °C). As a result, the resin system is expected to be employed in applications requiring high-temperature resistance and toughness.