Considering the actual working conditions of the motor, the potting adhesive used should have high thermal conductivity, good fluidity, cracking resistance, strong adhesion and other properties. Otherwise, it will be difficult to potting when used in automobile motor, which will increase the whole weight of automobile and cause the problem of high energy consumption ratio of automobile.
Suitable for electric vehicle for electronic components and power battery module potting sealant materials can be divided into: epoxy resin potting sealant; Silicone rubber sealant (silicone sealant); Polyurethane potting sealant. The following take epoxy resin potting sealant as an example to see what factors affect the performance of potting sealant.

Effect of filler on cracking resistance of potting sealant
Epoxy resin will shrink in the curing process. If the simple epoxy resin is used as electric potting, when the stress generated by the curing shrinkage of potting adhesive is greater than the bond between potting adhesive and the casing, it will cause peeling phenomenon. When the stress caused by curing shrinkage of potting adhesive is less than the bonding force between potting adhesive and casing and the potting adhesive strength is poor, potting adhesive cracking will be caused. Therefore, in order to avoid the occurrence of these phenomena, it is necessary to reduce the curing shrinkage rate of potting adhesive and increase the strength of potting adhesive, and adding a certain amount of filler into potting adhesive can effectively reduce the curing shrinkage rate of potting adhesive.
However, the amount of filler should not be too much or too little. The curing shrinkage rate of potting adhesive is high if the amount of filler is too low. Although the curing shrinkage rate of potting adhesive can continue to be reduced if the amount of filler is too low, the viscosity of potting adhesive will also increase greatly with the increase of filler.

Effect of filler on thermal conductivity and mechanical properties of potting sealant
Al2O3 is the most thermal conductive filler used in general thermal conductive materials; Metal nitrides with high thermal conductivity, such as SiN and AlN, are commonly used. The thermal conductivity of thermal conductive materials is not only related to the thermal conductive filler itself, but also closely related to the particle size distribution, morphology, interface contact, molecular bonding degree.
Generally speaking, the heat conduction effect of fiber or foil sheet heat conduction filler is better. In addition, the heat conductivity of potting adhesive prepared with filler with different particle sizes will be better. This is because a single particle size of filler particles not well continuous thermal channel is formed within the potting glue, there is gap between particle and particle, and between different particle size of filler particles, small particle size of packing is a good way to make up the gap between the larger particles filler, form a complete heat conduction channel, to achieve better heat transfer effect.

Effect of the amount of flame retardant on the properties of potting sealant
The addition of flame retardants can improve the flame retardancy of potting adhesives. At present, aluminum hydroxide and magnesium hydroxide are mainly used. However, when single aluminum hydroxide or magnesium hydroxide is used as flame retardant, the flame retardant effect is not as good as the combination of flame retardants. Moreover, the composite flame retardant can make the potting adhesive viscosity lower.
The reason why the combined use of flame retardant effect is better, may be because the decomposition temperature of aluminum hydroxide is about 250℃, the absorption of heat is 1965J/g, the decomposition temperature of magnesium hydroxide is above 300℃, they have good flame retardant performance, the flame retardant mechanism is mainly dehydration, heat absorption. When the temperature reach the decomposition temperature of aluminum hydroxide, the first aluminum hydroxide flame retardant effect can absorb a lot of heat, when the temperature rise further, magnesium hydroxide removal moisture also can have certain flame retardant effect, therefore the 1:1 compound with use can reduce the dosage of the flame retardant filler, it also ensures that the abnormal situation in the operation of the motor car in colloid not support combustion.

Effect of coupling agent on potting sealant properties
Appropriate viscosity can not only increase the fluidity of potting adhesive, improve the defoaming ability, but also improve the anti-settlement ability of the filler in potting adhesive, so as to ensure the stability of the product. The addition of coupling agent can effectively solve the above problems. According to the research, in the mixing process of resin and filler, the viscosity of resin in a certain range will decrease with the increase of the amount of silane coupling agent, until it tends to be stable.
In addition, the surface treatment of the thermal conductivity filler can also improve the thermal conductivity of the filler. By using its compatibility with the base adhesive and increasing the filling amount, the thermal conductivity of the potting adhesive can be greatly improved. For example, RTV thermal conductive silicone rubber is filled with corundum powder treated by silane coupling agent KH-550, A-151, hexamethyldisilazane and dimethyldimethoxysilane. The thermal conductivity of the material can be increased by 2.10 W /(m·K) from 1.16W /(m.K), and the thermal conductivity is nearly doubled.