Study On Preparation And Properties Of Polyvinyl Alcohol-based Composites With High Thermal Conductivitiy

With the advent of the 5G era,electronic devices are developing towards miniaturisation,integration,multi-function,and high power density,resulting in the generation of excessive heat,which puts forward higher requirements for the heat dissipation performance of electronic devices,as the accumulation of heat seriously affects their performance and even leads to their failure.Polymer-based thermal management materials have drawn much attention as they possess advantages in electrical insulation performance,flexibility,lightweight,high strength,etc,which have great application prospects in the field of microelectronic packaging.However,the intrinsic thermal conductivity of polymers is generally low and cannot meet the requirements of heat dissipation.Incorporating high thermally conductive fillers,such as alumina(Al₂O₃),magnesium oxide(Mg O),aluminum nitride(Al N),boron nitride(BN),silicon carbide(Si C),etc.,is an effective way to enhance the TC of polymers;it has the advantages of low cost,easy processing,industrial applicability,etc.The conventional method with randomly dispersed composite leads to heat flow in unintended directions in the composite,and limits the enhancement of thermal conductivity,due to the low probability of contact between fillers,and the high interfacial thermal resistance between fillers and polymer matrix.Forming continuous heat transporting paths of fillers in a polymer matrix as much as possible by rational structure design of fillers,which is believed to be the key to achieving high thermal conductivity composites.Based on this research idea,two aspects of work are carried out in this paper,the main contents are as following:(1)In this study,polyvinyl alcohol(PVA)/boron nitride nanoplatelets(BNNS)composites were fabricated with high in-plane TC via the combination of co-electrostatic spinning and spraying and hot-pressing technique.The high in-plane TC of the composites was due to the large lateral size of 2D BNNS,which was obtained via boric acid-assisted ball milling.Another paramount structural factor is the selective distribution of these BNNS on the surface of 1D PVA fibres.These interconnected BNNS are oriented along the in-plane direction after pressing,which construct continuous heat conduction pathways in the composites.Additionally,the in-plane TC of the composites shows obvious thickness dependence,that is,the in-plane TC increases with the decrease of the thickness of the composites.The in-plane TC reachs 19.99 W/(m·K)with a thickness of 30?m at BNNS fraction of40 wt%.Thus,this work provid a practical approach to fabricate ultrahigh in-plane TC composites,which will be used for the thermal dissipation of high power density electronic equipment.(2)Here,PVA/BNNS-Ag NW composites were fabricated with high in-plane TC via the combination of electrospinning and spraying and hot-pressing technique.Typically,BNNS can be arranged along fibers by electrospinning technique.Then spraying Ag NW on PVA/BNNS fiber film,a hybrid network oriented along the in-plane direction was constructed by Ag NW bridged BNNS in PVA/BNNS-Ag NW composite after hot pressing.The in-plane TC of the composites is significantly improved when a small amount of Ag NW is sprayed.In addition,PVA/BNNS-Ag NW composite exhibit good electrical insulation.The results demonstrated that PVA/BNNS-Ag NW composite show good heat dissipation capacity in the heat dissipation application of LED lights,so it has a great application potential in the heat dissipation of high-performance electronic devices.