Research And Application Of Surface Modification Of High Thermal Conductivity Filler

This article first studied the effects of modifier type and modifier dosage on the oil absorption value,activation index and particle size distribution of alumina powder,and determined the best modifier type and modifier dosage.Then the SEM and XRD characterization of the alumina powder before and after the modification found that the crystal structure of the modified alumina remained unchanged and the agglomeration phenomenon was reduced,and the dispersion was more uniform.Finally,the different proportions of vinyl silicone oil,different hydrogen-containing silicone oil,different modifier types,different modifier dosages,different particle size and shape alumina compound,single alumina and compound alumina are studied.The effect of different filling amounts and different filling amounts of single alumina and compound alumina after modification on various properties.Therefore,the formula and process of the silicone potting compound are optimized,and a high thermal conductivity silicone potting compound with good comprehensive performance is prepared.And compared the potting glue with similar potting glues from other manufacturers,and found that the overall performance of the potting glue is better.The main contents of this article are:(1)Dispersion process and curing process.The influence of dispersion time on the viscosity and thermal conductivity of the potting glue was studied by controlling the speed of the dispersing sand mill to 1500r/min.It was found that when the dispersion time was 6 minutes,the potting compound had lower viscosity and higher thermal conductivity.Through the research on the curing kinetics,gelation time and apparent activation energy of the potting glue,the best curing process and storage method are determined to be 70℃/1h,90℃/1h,and the two components A and B are separate Keep sealed.(2)The ratio of different vinyl silicone oils.By comparing the influence of vinyl silicone oil 500,vinyl silicone oil mass ratio 500:100=1:1 and vinyl silicone oil mass ratio 500:200=1:1 on the performance of potting glue.It is found that the potting compound prepared by the compound vinyl silicone oil with a mass ratio of500:100=1:1 has higher thermal conductivity,better heat resistance stability,mechanical properties and electrical insulation properties.(3)Different hydrogen-containing silicone oils.The influence of hydrogen-containing silicone oil with different active hydrogen mass fractions of0.05%,0.15%,0.32% and 0.5% on the thermal conductivity,heat resistance,electrical insulation and mechanical properties of silicone encapsulants was studied.It is found that the potting compound prepared by the hydrogen-containing silicone oil with the active hydrogen content of 0.32% has good thermal conductivity,heat resistance,electrical insulation and mechanical properties.(4)Alumina with different particle size is compounded.Two types of alumina,angular and spherical,are selected for this topic,and the particle size mass ratio is40μm:4μm:2μm=2:7:1,3:6:1,4:5:1,5:4:1,7:2:1 and 6:3:1 are compounded to compare their effects on the viscosity,thermal conductivity,heat resistance,electrical insulation and mechanical properties of the potting glue.It is found that the particle size mass ratio of 40μm:4μm:2μm=5:4:1 can form an effective accumulation,so the potting compound filled with the alumina powder with the particle size ratio has a relatively good overall performance.(5)Types of modifiers.In order to study the influence of the type of modifier on the oil absorption value and activation index of alumina powder,and to further improve the thermal conductivity of the silicone potting compound and reduce the viscosity of the potting compound.In this experiment,silane coupling agents KH560,KH570,CG9 and CG12 were used to modify the surface of alumina.The results show that the alumina powder modified by the silane coupling agent CG12 has a lower oil absorption value and a higher activation index,and the prepared potting compound has better overall performance.(6)The amount of modifier.By changing the dosage of silane coupling agent CG12 to 0.6wt%,1.2wt%,1.8wt% and 2.4wt% respectively,the oil absorption value,activation index,particle size distribution and the effect of single alumina and compound alumina powder were studied.The influence of various properties of the prepared potting glue.The results show that: a larger amount of modifier is likely to cause the powder to agglomerate,and a smaller amount of modifier makes the powder surface incompletely coated.Only an appropriate amount of modifier can achieve a better modification effect.The best modifier dosage for single alumina is 0.6wt%,and the best modifier dosage for compound alumina is 1.8wt%.(7)The filling amount of single alumina and compound alumina.By changing the filling amount of single alumina(respectively 0,40wt%,50wt%,60wt%,70wt%,75wt%)and the filling amount of compound alumina(respectively 0,50wt%,60wt%,70wt%,75wt%,82wt%)to study its influence on various properties of potting glue.The results show that with the increase of the filling amount,the viscosity,thermal conductivity and heat resistance of the potting glue prepared from single alumina and compound alumina increase.The volume resistivity and breakdown strength both decrease,the tensile strength first increases and then decreases,and the elongation at break gradually decreases.Under the premise of ensuring good flow and processability,the maximum filling amount of compound alumina(82wt%)is higher than that of single alumina(75wt%),and the overall performance of the filled potting compound is better than that of single alumina.(8)The filling amount of single alumina and compound alumina after modification.The silane coupling agent CG12 was used to modify single alumina and compound alumina.The amount of modifier used for a single alumina is 0.6wt%,and the amount of modifier used for compound alumina is 1.8wt%.The results showed that the maximum filling amount of single alumina and compound alumina after modification(80wt% and 87wt% respectively)increased by 5wt% compared with that before modification.With the single alumina filling amount after modification(respectively 50wt%,60wt%,70wt%,75wt%,80wt%)and compound alumina filling amount(respectively 60wt%,70wt%,75wt%,82wt%,87wt%)increase,changes in various properties and It is the same before modification,and the comprehensive performance of the potting adhesive after modification is better than that without modification.