A brief account of how silicone potting compounds can help lightweight new energy vehicles.
Source:360 Author:QL CHEMICAL Release time:2022-12-27 11:47 Reading times:51
In recent years, automobile lightweight is a hot trend in the development of the automobile industry. Especially for new energy vehicles, the huge battery system increases the overall weight of the vehicle body, seriously affecting the cruising range, and the development of lightweight vehicles is an inevitable choice. Relevant domestic policies require that by 2017, new energy vehicles will achieve a 25% reduction in body weight through the application of new materials, and a 30% reduction in body weight by 2020.
The main means to realize the lightweight of automobiles are the application of lightweight new materials, optimization of body structure design, and introduction of advanced manufacturing processes.
So, how does the new material help the new energy vehicle lightweight from the battery system?

1. What is silicone potting glue?

Silicone potting adhesive has good high and low temperature resistance, weather resistance and corrosion resistance, and is widely used in the field of packaging of electronic appliances. However, pure silicone potting compound itself has poor thermal conductivity and is flammable (the limiting oxygen index is about 18%), so it is necessary to add thermally conductive fillers and inorganic flame retardants to obtain better thermal conductivity and flame retardancy. At present, commonly used thermally conductive fillers include alumina, zinc oxide, boron nitride, and silicon micropowder.
Room temperature vulcanized silicone rubber or silicone gel is used for the potting of electronic and electrical components, which can prevent moisture, dust, corrosion, and shock, and improve the performance and stability parameters, and it is liquid before vulcanization, which is convenient Prime and easy to use.
When using silicone gel for potting, no low molecular weight is released, no stress shrinkage, deep vulcanization without any corrosion, it becomes a transparent elastic body after vulcanization, the components encapsulated in the glue layer are clearly visible, and can be pierced with needles Go inside to measure component parameters one by one, which is convenient for inspection and repair. Room temperature vulcanized foamed silicone rubber is used for memory core boards in electronic computers, and it fully meets the requirements after many tests such as vibration, impact, and alternating heat and cold.
The flame-resistant potting compound prepared on the basis of addition-type room temperature vulcanized silicone rubber is very effective for molding high-voltage caps for TV sets and sheaths for high-voltage cables. When it is not necessary to carry out airtight packaging or it is inconvenient to carry out impregnation and potting protection, one-component room temperature vulcanized silicone rubber can be used as the surface coating protection material. Generally, the surface protection coating of electronic components is made of room temperature vulcanized silicone rubber and internally coated with addition-type silicone gel.

2. How silicone potting adhesives can help lightweight vehicles
1. The structure of the new energy vehicle battery system is as follows:

The entire battery board consists of multiple lithium batteries to form a single battery pack, the battery packs form a battery pack, and the battery packs form a battery board. When the car is running at high speed, due to the bumps, the internal shaking of the battery is relatively severe, and the battery will release a lot of heat when it is working. Therefore, the potting adhesive needs to solve the problems of connection and heat dissipation between batteries, and must have the characteristics of shock absorption, bonding and fixing, insulation, and flame retardancy.
In order to meet the above requirements, the industry has introduced heat-conducting and flame-retardant silicone potting compounds.

2. The role of silicone potting compound in new energy vehicle batteries

The silicone potting material itself has many polar functional groups, which can interact with the polar groups on the surface of the plastic of the battery case and the aluminum part of the battery case, thereby playing the role of bonding and fixing. Moreover, the silicone potting compound has good elasticity after curing, so as to meet the shock absorption requirements.
In addition, the silicone potting compound can obtain good thermal conductivity and flame retardant properties by adding heat conducting agents and flame retardants, which can effectively dissipate heat for the battery pack and cells, improve the working temperature of the batteries; and protect the key electronic components, cells and batteries inside the battery. Bus bar, to avoid the danger of power surge and battery fire, and solve the problems of heat dissipation and flame retardancy.

3. How silicone heat-conducting potting compound can help reduce the weight of automobiles

According to statistics, the weight of battery panels in a new energy vehicle for household use is about 150-400kg, and the amount of silicone heat-conducting potting glue used is about 20-50kg. The commonly used silicone potting adhesives at this stage use alumina, silicon micropowder, etc. as thermal conductive fillers, and the specific gravity of the adhesive is usually 1.8-2.2g/cm3. Its performance requirements are: thermal conductivity 0.4-0.8W/m*K, flame retardancy up to UL94 V-0 or V-1, and good fluidity.
If the specific gravity of the glue is reduced to below 1.6g/cm3, the weight of the glue will be reduced by 10-30% under the same filling volume. Based on the amount of 50kg potting glue, it can be reduced by 5-15kg. The weight of "5-15kg" is of great significance to the lightweight of automobiles in terms of the use of new materials, structural design and technology.

Take the lightweight development of Audi TT as an example: the second generation of Audi TT is 30kg lighter than the first generation, and the third generation will continue to lose 17kg on the basis of the second generation. The weight reduction depends on the use of aluminum alloy materials. The use of aluminum alloys accounted for 35.8%, and steel accounted for 21.6%. However, the use of magnesium-aluminum alloys increases the cost of the car by about 130 yuan per kilogram of weight loss, and the cost of carbon fiber reinforced composite materials increases by more than 180 yuan per kilogram of weight loss; breakthroughs in the connection of steel and aluminum require a lot of advanced connection technology to support The manufacture of the steel-aluminum hybrid body must meet various performance requirements at the same time. And by reducing the specific gravity of silica gel to achieve light weight of the car will hardly increase the cost. It can be seen that reducing the proportion of silicone potting compound is very meaningful for the development of automobile lightweight.

3. How to reduce the proportion of silicone potting compound
Most silicone potting compounds on the market use aluminum oxide, aluminum hydroxide, silicon dioxide, etc. as thermal conductive fillers. These traditional materials are difficult to effectively reduce the specific gravity while ensuring thermal conductivity. The emergence of aluminosilicate (xAl2O3·ySiO2·zH2O) breaks this barrier. It not only has good thermal conductivity, but also has a lower specific gravity of the powder because it is rich in hydroxyl groups. And during the combustion process, it can release crystal water, so it has another important characteristic - flame retardancy.
At present, the preparation technology of this material is mastered by local companies. The company's related products have also been mass-produced. The series of products are developed for potting products with a specific gravity of 1.6g/cm3, 1.4g/cm3, and 1.2g/cm3 respectively. The thermal conductivity can reach 0.4-0.6W/M*K, and both can reach UL94 V-0.
The specific gravity of the potting compound prepared from the above-mentioned low specific gravity thermal conductive powder is 10%-30% lower than that of conventional products, which can effectively reduce the weight of new energy vehicle battery packs, thereby helping to reduce the weight of vehicles.

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