High-performance main-chain polybenzoxazine composites by incorporating multi-walled carbon nanotubes with different surfacial structure: Mechanical properties, thermal stability and mechanisms

Herein, multi-walled carbon nanotubes (MWCNTs) with different surfacial structure were first designed and synthesized, and then incorporated into main-chain polybenzoxazine (PBZ) to fabricate PBZ composites. Fourier transform infrared results showed that the ring-opening crosslinking process of benzoxazine (BZ) oligomer was catalyzed due to the existence of  COOH and  NH 2 groups on the surface of MWCNTs. The enhanced interface interactions between MWCNTs- f BZ and PBZ contributed to the improvement of the mechanical properties. When the MWCNTs- f BZ content was 1.5%, the MWCNTs- f BZ/PBZ composites had excellent tensile strength of 102.64 MPa. The highest impact strength, which was 15.96 kJ/m 2 and 64.15% higher than that of neat PBZ at 1.5% MWCNTs- f BZ was achieved. Through the Halpin-Tsai equation, combined with the experimental results, the correction factor was obtained to predict the mechanical properties. FESEM observations showed that the dispersion of MWCNTs in the PBZ matrix depended on the functional groups of MWCNTs. TGA tests and Horowitz-Metzger calculation found that the thermal decomposition temperature of the composites reached 451.7°C and had the highest decomposition activation energy of 153.20 kJ/mol at 2% MWCNTs- f BZ. In summary, the obtained MWCNTs- f BZ/PBZ composite showed excellent comprehensive performance and can potentially be used as advanced engineering material in demanding environments.