Natural rubber composites with enhanced thermal conductivity fabricated via modification of boron nitride by covalent and non-covalent interactions

Hexagonal boron nitride (BN) platelets are often used as fillers to improve the thermal conductivity (λ) of polymer matrix composites thanks to their good insulation and relative high λ. However, the low compatibility between polymeric matrices and BN platelets results in interfacial phonon scattering, interfering with the composites' heat transfer. In this paper, functionalized BN platelets were first modified with poly(catechol/polyamine) (PCPA) and then grafted with bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) to yield BN-PCPA-Si69/natural rubber (denoted as BN-PCPA-Si69/NR) composites. PCPA coating declined the interfacial phonon scattering between the matrix and fillers, while silane grafting improved the interfacial interaction via NR vulcanization with tetrasulfide bonds in Si69. In turn, these features led to improved dielectric characteristics, thermal conductivities, and mechanical properties. Among prepared samples, NR composite filled with 30% volume BN-PCPA-Si69 platelets content yielded a thermal conductivity 5.4-fold higher (λ = 0.81 W/mK) than that of neat NR (λ = 0.15 W/mK). The mechanical performances of BN-PCPA-Si69/NR composites also improved significantly with the maximum tensile strength reaching up 17.0 MPa. In sum, the proposed method looks inexpensive and feasible for the fabrication of high thermal conductive polymer composites for use in future advanced electronic devices, such as insulating and packaging electronic materials.