Ultra‐fast curing of benzoxazine with surface modified fly ash‐assisted microwave: Achieving excellent comprehensive performances

Abstract Benzoxazine has aroused a lot of research interest because of its high mechanical performance and excellent thermal stability in polybenzoxazines. However, it suffers from its high curing temperature and long curing time, which necessitate resolution. This study addresses this issue by employing a surface‐modified fly ash‐assisted microwave curing method to achieve ultra‐fast benzoxazine curing within 15 min. The impact strength of the resulting cured product displayed an increasing‐then‐decreasing trend with the addition of fly ash, reaching a maximum impact strength of 18.71 ± 1.20 kJ/m² at a 3% fly ash content. This value is 113.3% higher than the impact strength of pure PBA‐a. Additionally, when using the same amount of fly ash, the microwave‐cured product exhibited a flexural strength of up to 135.9 MPa and a flexural modulus of up to 6.71 GPa, surpassing those of pure PBA‐a by 28.7% and 33.1%, respectively. Moreover, the glass transition temperature (T_g) increased by 19.56°C. Furthermore, there was a slight improvement in flexural strength compared to the heat‐cured product, and no significant loss in thermal properties was observed. The method demonstrated in this study presents a novel approach for the rapid molding and preparation of benzoxazine in composites.