Multifunctional Graphene/Carbon Nanotubes/Poly(Butylene Terephthalate) Composites With Flame Retardancy, Wave Absorption, and Improved Mechanical Properties

ABSTRACT The development of processable materials that integrate flame retardancy, mechanical robustness, and microwave absorption for use in next‐generation high‐density electronic devices remains a critical challenge. This study reports on multifunctional graphene/carbon nanotube/polybutylene terephthalate composites fabricated via melt blending. The influence of graphene content on the flame retardancy, microwave absorption, and mechanical performance of the resulting composites was investigated. Flammability testing demonstrates that the incorporation of 2 phr of graphene significantly improves fire resistance, upgrading the UL‐94 rating from V‐2 (3.2 mm) to V‐0 (1.6 mm) and increasing the glow wire ignition temperature by 25°C. Cone calorimetry and scanning electron microscopy–energy‐dispersive X‐ray spectroscopy results indicate that graphene promotes char formation and suppresses volatile flammable gas release. Regarding microwave absorption, graphene facilitates the formation of a robust conductive network, yielding a minimum reflection loss of −15.31 dB at 12 GHz with a thickness of 2.8 mm. Mechanical characterization reveals that the incorporation of 2 phr of graphene enhances the tensile, flexural, and impact strengths by 13.2%, 9.5%, and 50%, respectively. Because of these integrated properties, the composite is a promising candidate for industrial systems requiring both safety and multifunctionality.