Design,Preparation And Performance Research Of Flexible Thermally Conductive Elastomer Matewials

Focusing on the design of advanced thermal management materials with high thermal conductivity,high stability and multi-function as the performance goal,this paper studies the compounding of traditional thermal conductive fillers and the leakage of new thermal conductive fillers liquid metal(LM).On the one hand,we designed LM particles with core-shell structure to solve the leakage problem of LM/elastomer composites;on the other hand,combined with computer modeling method,we developed a set of multi-component spherical thermal conductive filler composite model to guide the preparation of high-performance thermal interface materials.The main contents and achievements of this paper are as follows:(1)Design,preparation and characterization of boron nitride coated liquid metal(LM@BN)core-shell structure fillers: the effects of different media and methods on the dispersion process of LM were investigated.All kinds of LM particles were observed by optical microscope and scanning electron microscope,and the LM particles with suitable particle size distribution were obtained.Mercapto boron nitride(BN-S)was prepared by modification of boron nitride(BN).The structure of BN-S was confirmed by infrared spectroscopy,X-ray photoelectron spectroscopy,thermogravimetric analysis,X-ray diffraction and scanning electron microscopy.After analyzing the XPS spectra of N and S atoms in LM@BN,the S-Ga and N-Ga interaction between BN-S and LM was confirmed.(2)Preparation and properties of LM@BN/PDMS composites:LM@BN/PDMS composites were prepared based on LM@BN core-shell structure particles.The material has a broad application prospect in the field of flexible thermal management.LM@BN/PDMS has excellent thermal conductivity and the thermal conductivity reaches 3.2W/ m K after tensile training.LM@BN/PDMS has extremely stable dielectric properties,and its volume resistivity is always higher than 108 ? / m,whether after stretching to 100 % strain or after LM solidification at ultra-low temperature(-80 ℃).The hardness of LM@BN/PDMS decreases with the increase of filler content,and it is only 28 HA when the filler content is 50 %.LM@BN/PDMS has excellent stability and can work stably under the pressure of 70 psi and high and low temperature cycle without leakage.(3)Guiding the preparation of high-performance polymer-based thermally conductive composites based on the most dense stacking theory: The packing problem of spherical thermal conductive fillers is abstracted as a spherical packing model in three-dimensional space.By introducing Dinge-Funk equation(D-F equation),we design a set of models to find the optimal combination of fillers.This model can not only select the optimal particle size combination of many kinds of fillers,but also deal with fillers with non-normal distribution.Five kinds of alumina thermal conductive fillers with different particle sizes were selected,and the difference between filler composition and D-F equation was analyzed by least square method,so as to select the best type selection and optimal ratio.The experimental results show that using the composite formula optimized by the model,the thermal conductivity of the composite can reach 4.07W/ m K,which is81.1 % 110.7 % higher than that of the single particle size formula,which is the best of all the compounding schemes.