Polyamide Acid–Based Surface Modification of Poly(p‐Phenylene Benzobisoxazole) Fibres Reinforcing Syntactic Foam for Using Them as High‐Performance Insulating Core Material

ABSTRACT The insulating core is an important part of pillar composite insulators used in power transmission systems. Traditional insulating core materials suffer from various problems that can threaten the reliability of insulated equipment. Syntactic foam (SF) exhibits excellent properties, such as a low density, water penetration resistance and high dielectric strength, and has considerable application potential. However, its poor thermal conductivity and toughness make it prone to cracking. The thermal conductivity and toughness of SF can be improved by employing poly(p‐phenylene benzobisoxazole) (PBO) fibres as the reinforcing phase; however, the chemical inertness of these fibres makes them poorly compatible with epoxy resin. Herein, PBO@polyamide acid (PAA) fibres were obtained via the PAA‐based surface modification of the PBO fibres, and PBO@PAA‐fibre‐reinforced SF materials were prepared and analysed for their comprehensive performance. Experimental results showed that the interfacial shear strength of the modified fibres was enhanced by 18.2%. Furthermore, molecular dynamics simulations verified the effectiveness of interfacial modification. In addition, the reinforcement of the involved SF materials by the modified fibres improved their thermal conductivity, tensile strength, flexural modulus and impact strength by 39.3%, 24.9%, 24.3% and 56.3%, respectively. Overall, these results are expected to promote the development of new insulating core materials.