Construction Of Three-dimensional "Bridge-bonding" Thermally Conductive Networks Of Hexagonal Boron Nitride/Multi-wall Carbon Nanotubes Or Hexagonal Boron Nitride/Graphene In Isotactic Polypropylene

Isotactic polypropylene?iPP?has important applications in daily life,industry,national defense and other fields due to its good thermostability,processability and insulativity.The application of iPP in some electronic devices,such as light-emitting diode?LED?devices,batteries and communication equipments,is limited by its poor thermal conductivity?TC?,which is only about 0.23 W m^-1K^-1.The hexagonal boron nitride?h-BN?nano particles were selected as the main thermal conductive fillers to melt with iPP in this article to improve the TC of iPP.In addition,one-dimensional?1D?multi-wall carbon nanotubes?MWCNTs?and tow-dimensional?2D?graphene nanoplatelets?GNPs?,both of which have excellent TC,were slightly combined with h-BN nano particles respectively to form three-dimensional?3D?thermally conductive networks in the composites to improve the TC of iPP.?1?The different contents of h-BN nano particles were melt with Maleic anhydride grafted polypropylene?MAPP?,which is used as a compatibilizer,and iPP to form the iPP/MAPP/h-BN composites.The structure and properties of the iPP/MAPP/h-BN composites were analyzed by scanning electron microscopy?SEM?,thermal constants analyzer,high electric resistor,universal tensile test,rotational rheometer and dierential scanning calorimeter?DSC?.The results showed that the addition of MAPP can improve the TC of composites effectively,especially with high content of h-BN nano particles.The TC of the iPP/MAPP/h-BN composites with 30w.t.%h-BN nano particles show 9.3%enhancement by incorporation of MAPP.The adverse effects of phonon scattering are reduced further and the compatibility and interfacial interaction between h-BN nano particles and iPP are improved by adding MAPP.?2?The composites have poor TC at low contents of h-BN particles and poor mechanical properties at high contents of h-BN particles.To solve those problems,the1D MWCNTs and h-BN nano particles were fabricated in iPP matrix to form thermally conductive networks effectively.And the structure and properties of the composites were studied by SEM,thermal constants analyzer,rotational rheometer,DSC,universal tensile and testhigh electric resistor.The results showed that the TC of iPP/MAPP/h-BN composites was enhanced with less MWCNTs.The isolated h-BN aggregates could be“bridged”by 1D MWCNTs to form 3D thermally conductive networks effectively.The composites have a good electric insulativity,Young's modulus and tensile strength at same time.?3?The 2D GNPs also have excellent TC and it was fabricated with h-BN nano particles to study the difference of 3D thermally conductive networks which is“bridged”by h-BN nano particles and different dimensional carbon nanomaterials in iPP matrix.The microstructure and properties of iPP/h-BN/GNPs composites were also studied by SEM,thermal constants analyzer,high electric resistor,universal tensile test,rotational rheometer and DSC.The results indicated that the 2D GNPs with large surface area and higher TC improved the Young's modulus and TC of composites through forming 3D thermally conductive networks with h-BN particles more easily than 1D MWCNTs under the same content.Besides,the iPP/h-BN/GNPs composites have a better electrical insulation than iPP/h-BN/MWCNTs composites with the same quality fraction of hybrid fillers.