Pickering Emulsion-like Preparation Of Boron Nitride/Polypropylene Thermally Conductive Composites And Its Thermal Conductivity

With the rapid growth of electronic equipment performance,there has been a growing demand for insulation thermal management in equipment.Therefore,it is of great significance to improve the insulation and thermal conductivity of thermoplastics commonly used in electronic components.In order to reduce the amount of thermally conductive filler and improve the thermal conductivity of the composite material while ensuring its mechanical strength,boron nitride(h-BN)coated polypropylene(PP)beads were prepared by a Pickering-like emulsion method.After compression,h-BN/PP composites with three-dimensional thermal conduction paths were obtained.Boron nitride nanosheets(BNNSs)were stripped using SC CO₂ to obtain thermally conductive fillers with higher thermal conductivity which can improve the thermal conductivity of the composites.Finally,dopamine(DA)modify BNNSs were used to enhance the interface between the filler and the matrix,which can further improve the thermal conductivity of the composite.The main work of this paper are as follows:(1)H-BN-coated PP beads were prepared by a Pickering-like emulsion method.And the composites were obtained by hot pressing at different temperatures.H-BN were uniformly and densely coated on the surface of PP particles.The shape of PP was regular spherical after coated with h-BN.A network structure composed of h-BN can be observed in h-BN/PP composites.The viscosity and relaxation time of the composites increased as the h-BN amount increased.The thermal conductivity of the composite material was 0.45 W/(m·K)with 10.1 wt%h-BN contentde.The thermal conductivity of PP increased by 114.3%,which was higher than the thermal conductivity of composites obtained by melt blending and powder mixing at the same filler content.(2)H-BN was stripped with SC CO₂,and scanning electron microscope(SEM),transmission electron microscope(TEM),Raman spectroscopy(Raman),X-ray diffractometer(XRD),and X-ray electron spectrometer(XPS)proves that a small number of single or multiple BNNSs have been stripped.The thermal conductivity of the composite was 1.71 W/(m·K)with 10.1 wt%BNNSs filled,which was 713%higher than that of pure PP.And the tensile strength&impact strength of the composite were 33.7 Mpa,12.3 KJ/m² respectively.(3)Non-covalent bond modification of BNNSs by DA.That the surface of PDA@BNNSs became rough,and the edges of BNNSs had a thin PDA layer with a thickness of about 18 nm.The modified BNNSs are more tightly bound to the matrix,which reduces the interface thermal resistance caused by the interface.When the content of PDA@BNNSs is 10.1 wt%,the thermal conductivity of the composite was1.8 W/(m·K),which was 0.1 W/(m·K)higher than that of BNNSs/PP composites with the same content.This modification also improved the mechanical properties of the composite material,and its tensile strength and impact strength reached 34.15 Mpa and12.9 KJ/m²,respectively.