Preparation Through Salt-templated Method And Thermal Property Research Of BN/Polymer-based 3D Composites

In today’s technological era,electronic chips play a pivotal role in shaping human life.However,the continual accumulation of heat poses significant challenges to the optimal performance of these chips.Consequently,the need for high performance thermal management materials is pressing.Currently,research efforts are focused on emerging filler-type thermal conductive polymer materials characterized by high thermal conductivity,high integration,and high density.Among these materials,hexagonal boron nitride has garnered significant attention due to its graphene-like structure and unique electrical insulation properties.In this regard,boron nitride microsheets serve as thermal conductive fillers,with a salt-template method adopted to facilitate the design of a thermal conductive microstructure.This approach constructs a heat conduction channel in the composite material,thereby improving its thermal conductivity.The main work content and results of this thesis are as follows:（1）Through the salt-template method,boron nitride（BN）microsheets were connected by Polymethylmethacrylate（PMMA）to rapidly prepare a cellular-shaped BN/PMMA thermal conductive skeleton.Then,the BN/PMMA thermal conductive skeleton was impregnated into epoxy resin（Ep）through a vacuum-assisted method to prepare BN/PMMA/Ep thermal conductive composite material.At a BN loading amount（wt%）of 30%,the thermal conductivity reached 0.487±0.02565 Wm^-1K^-1,which was a 260%improvement compared to PMMA/Ep materials.The best comprehensive mechanical properties were achieved at a BN loading of 12 wt%,with a tensile strength of 0.9132±0.0182 MPa,a Young’s modulus of 9.35±0.468 GPa,and a toughness of 0.804±0.02 MJ·m^-3.（2）By exploring the influence of salt type and morphology on the thermal conductivity of the composite material,a suitable salt was chosen as the sacrificial template to prepare a cellular-shaped BN/thermoplastic polyurethane（TPU）skeleton.Then,BN/TPU/Ep thermal conductive composite material was prepared by hot pressing and infusion of epoxy resin.At a BN loading amount（wt%）of 30%,the thermal conductivity reached 0.534±0.0248 Wm^-1K^-1,which was a 244%improvement compared to TPU/Ep materials.The comprehensive mechanical performance was best at a BN loading（wt%）of 18%,with a tensile strength of4.18±0.21 MPa,a Young’s modulus of 2.42±0.121 GPa,and a toughness of 1.06±0.503MJ·m^-3,（3）30μm-sized silver nanowires（Ag NWs）were prepared by an oil bath method,and Ag NWs-BN thermal conductive filler was compounded to prepare Ag NWs-BN/TPU/Ep thermal conductive composite material using the salt-template method and hot pressing infusion of epoxy resin.At an Ag loading amount（wt%）of 0.9%,the thermal conductivity reached 0.838±0.042 Wm^-1K^-1,which was a 56%improvement compared to BN/TPU/Ep materials without Ag NWs.Meanwhile,the mechanic property is improved by adding Ag NWs.