Surface engineering of carbon fibers via layer-by-layer graphene oxide grafting: Interface regulation and thermal conductivity enhancement of aligned continuous carbon fiber/natural rubber composites

Abstract

Natural rubber (NR) suffers from intrinsically low thermal conductivity and poor heat dissipation, which can be mitigated by constructing efficient heat transfer pathways using highly thermally conductive fillers. In this work, a three-dimensional thermally conductive network was developed within the NR matrix by synergistically incorporating polydopamine (PDA) and silane coupling agent co-modified ground carbon fibers (CF) together with oriented continuous CF grafted with graphene oxide (GO). This architecture significantly enhanced both the thermal conduction capability and interfacial performance of the composites. Specifically, PDA was first adsorbed onto CF surfaces as a secondary reaction platform, followed by coating with polyethyleneimine (PEI) via Michael addition. GO was subsequently grafted onto the fibers through electrostatic adsorption or acylation-based covalent bonding. Adding 1 phr GO(3)-CF (continuous CF with three electrostatically adsorbed GO layers) increased the thermal conductivity from 0.320 W/(m·K) to 0.383 W/(m·K) (19.7% rise), while GO-CF (covalently bonded with one GO layer) reached 0.394 W/(m·K) (23.1% rise). The thermal conductivity along the orientation direction of GO(3)-CF was 113.3% of the radial value. After 15 min of heating, the surface temperature of neat NR composites rose only from 32 °C to 59 °C, compared to 69.3 °C for GO(3)-CF/NR and 72.2 °C for GO-CF/NR. Pull-out forces of GO(3)-CF and GO-CF cords increased by 86.8% and 102.5% versus unmodified fibers, respectively, indicating reduced phonon scattering sites and lowered interfacial thermal resistance. Multiscale finite element simulations revealed the underlying mechanism, confirming that the enhancement effect of layer-by-layer self-assembly has a theoretical upper limit and does not increase indefinitely with the number of layers. These findings demonstrate the potential of such composites for applications in flexible thermal management, thermal protection, and heat dissipation.