The effect of hybrid thermal fillers on thermal conductivity of carbon fiber reinforced polybutylene terephthalate composites

The use of functional polymeric composites with superior thermal properties, capable of replacing conventional polymers, has increased in recent years, particularly in the electrical‐electronics sector where thermal management is crucial. Carbon fiber (CF) polymer–matrix structural composites have relatively high in‐plane thermal conductivity but low through‐plane conductivity. In order to further enhance the through‐plane and in‐plane conductivity of CF‐reinforced polybutylene terephthalate (PBT) composite, a hybrid loading approach was employed, incorporating synthetic graphite (SG), boron nitride (hBN), aluminium nitride (AlN) and graphene (G) in composite formulations. It was found that the in‐plane conductivity of PBT‐20CF‐20SG‐3G and the through‐plane conductivity of PBT‐20CF‐20SG‐3AlN are 69% and 25% higher, respectively, than those of PBT‐40CF. However, the mechanical properties of hybrid composites exhibit lower values compared to those of CF‐reinforced PBT composites. The tensile strength value of PBT‐40CF is about 33% and 57% higher than those of PBT‐20CF‐20SG‐3G and PBT‐20CF‐20SG‐3AlN. Moreover, the flexural strength of PBT‐40CF is about 48% and 38% higher than those of PBT‐20CF‐20SG‐3G and PBT‐20CF‐20SG‐3AlN, respectively. The density value of PBT‐40CF is lower than that of the composites of PBT‐20CF‐20SG. From TGA it was observed that the thermal stability of PBT‐40CF is comparable to that of the composites PBT‐20CF‐20SG. From the conducted study, it can be proposed that the hybrid combination of SG, hBN, AlN and G can be utilized to achieve higher thermal conductivity values, instead of relying solely on CF in the composites. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. A combination of various fillers with different aspect ratios should be used to create an effective thermal conductivity network.