Preparation And Properties Of Silicone Composites Based On Double Intersection Network

Contemporary electronic equipment tends to develop with high integration and high power,and the contradiction between the rapid accumulation of heat and the small cooling space has become one of the main obstacles to the operation of electronic equipment.Thermal interface material is a key part of thermal management technology.Due to the mechanical damage in the working process,the thermal conduction path is interrupted,which affects the thermal conductivity and even causes safety problems.Therefore,the development of thermal interface materials with self-healing properties can make thermal interface materials self-healing damage in the work has important practical significance.In this work,Al₂O₃@SR/SCNR composite with high thermal conductivity and rapid self-healing was prepared by in-situ blending method.The matrix of the composites consists of thermosetting silica gel matrix(SR)and thermoreversible matrix(SCNR).Spherical Al₂O₃ fillers with different particle sizes and SCNR particles were introduced into SR system to construct Al₂O₃@SR/SCNR composites.By adjusting the SR/SCNR ratio,the obtained composites can achieve flexibility,self-healing and high filling at the same time.The main research contents are as follows:(1)The composition and ratio design of single cross-linked network thermal conductive gel were explored.The proportion of vinyl silicone oil and hydrogen silicone oil determines the oil permeability of thermal conductive gel.The hydrogen-containing silicone oil can be divided into cross-linking agent side chain hydrogen-containing silicone oil and chain extender end hydrogen-containing silicone oil according to the role.The ratio of the two has a direct impact on the hardness and elasticity of the thermal conductive gel.Therefore,the study on the silicone oil ratio of the silicone matrix of the thermal conductive gel is an important link to improve the comprehensive performance of the thermal conductive gel.Firstly,the single factor experiment was designed to study the optimal ratio of hardness and elasticity of thermally conductive gel with the ratio of side hydrogen silicone oil to end hydrogen silicone oil as the variable.Then on the premise of determining the ratio of side hydrogen silicone oil and end hydrogen silicone oil,the rheological properties and oil permeability of the eight groups of samples were investigated with the ratio of vinyl silicone oil and hydrogen silicone oil as a single variable.Using spherical alumina as thermal conductive filler,the effect of filler loading on thermal conductivity was studied.The actual heat transfer and heat dissipation performance of thermal conductive gel was studied.Optimum ratio of thermal conductive gel.(2)Through the classic hydrosilylation reaction,ester-based functional groups were grafted on the side-chain hydrogen-containing silicone oil,and PDMS-COOH was obtained by hydrolysis reaction.The PDMS-COOH and PDMS-NH₂ were crosslinked to obtain the silicone elastomer SCNR with thermal reversible crosslinking network.The structure was characterized by FT-IR and ~1HNMR,and the dynamic behavior of its carboxyl-amino dynamic bond was characterized and analyzed by in-situ infrared and rheological properties.The self-healing properties of the samples were studied.SCNR can be self-healing at 90?for 1 h,and can be reshaped after hot pressing at 90?for 15 min and 2 k Pa.Its rapid self-healing mainly comes from the dissociation and reconstruction of amine-carboxyl dynamic bond and hydrogen bond.(3)Al₂O₃@SR/SCNR composites were prepared by in-situ blending-rolling method.The results showed that when the addition amount of SCNR component was6.7 wt%,the thermal conductivity was 5.86 W/m K,and the self-healing efficiency was95.6%within 3 min.The mechanism of the synergistic effect of thermal conductivity and self-healing is that the weak reversible non-covalent bond in SCNR is interconnected with the SR covalent cross-linked network of the first cross-linked network,and the silicone thermal conductive gel with fast self-healing performance of the double cross-linked network is constructed.These fast self-healing behaviors benefit from the auxiliary effect of thermal diffusion in the three-dimensional heat conduction pathway on the dynamic cross-linked network rearrangement.