Preparation And Thermal Conductivity Of Hexagonal Boron Nitride Nanosheet/Polymer Composite

Nowadays,efficient heat dissipation is an indispensable function in electronic devices and wearable textiles.However,polymer materials have become ideal candidates for thermal conductivity materials due to their high insulation,ease of molding,and easy processing.However,the intrinsic thermal conductivity coefficient of polymer materials is too low,limiting their applications in high thermal conductivity requirements.Therefore,it is urgent to improve the thermal conductivity of polymer materials.Hexagonal boron nitride nanosheets(h-BNNSs)are considered as one of the ideal materials to improve the thermal conductivity of polymer materials due to their excellent mechanical strength,outstanding thermal conductivity,low density,excellent insulation,and prominent chemical stability and high-temperature oxidation resistance.This paper is mainly based on h-BNNSs to prepare high thermal conductivity composite materials and explore the thermal conductivity,mechanical strength,and thermal stability of h-BN/polymer composite materials.The specific research content were summarized as follows:1.High thermal conductivity composite fibers of h-BNF/PET were prepared through a one-step melt blending and spinning process.Firstly,hexagonal boron nitride nanosheets(hBNF)were prepared by ultrasonic method,and then h-BNF was incorporated into PET matrix to construct a h-BNF-based thermal conductive pathway to improve the thermal conductivity of PET.The thermal stretching during the preparation process enabled the h-BNF to be aligned and form an excellent thermal conductive pathway in the PET matrix,resulting in an axial thermal conductivity of 1.397 W/(m·K).In addition,this composite fiber has good flexibility,mechanical properties and thermal stability performance at the same time.In the process of being woven into fabric simulating thermal cycling,it shows good cyclic thermal stability,and the actual human body heat can also quickly transfer heat to the surface of the fabric and exchange heat with the environment,and these excellent properties have broad application prospects in personal cooling wearable fabrics.2.High thermal conductivity BNNS@PDA/PI composite thermal conductive materials were prepared by modifying boron nitride nanosheets(BNNS)with polydopamine(PDA).The modification successfully resulted in highly dispersed BNNS@PDA nanomaterials.By rationally assembling BNNS@PDA and PI matrix,both in-plane and out-of-plane thermal conductivities were improved to 7.42 W/(m·K)and 3.03 W/(m·K),respectively.At the same time,BNNS@PDA/PI composites also have high thermal stability over 510 °C,low coefficient of friction and high insulating properties with high volume resistance performance.In addition,BNNS@PDA/PI films have high transparency,good flexibility and excellent shape memory properties,and the response time is more shorter than the pure PI films under thermal conductivity conditions.Therefore BNNS@PDA/PI films have a greater application prospect in flexible electronic devices.