Silicone foam material is a kind of porous, low-density, low-density, low-density, high-porous, low-density, silicone foam material that is made from silicone raw rubber, fillers, vulcanization accelerators, foam rubber, etc. Compressible polymer. Elastomer. Because it has the high elasticity of silicone rubber and has the sound insulation and shock-absorbing properties of foam materials, it is widely used in daily life. It is mostly used as vibration-absorbing pads, sealing gaskets, sound-absorbing materials, insulation layer materials, and airline thermal insulation materials. According to the cell structure, silicone foam is divided into three types: closed cell type, open cell type and mixed type.
1.Density of silicone foam
The density of the silicone foam matrix is 1.17g/cm3. However, through foaming treatment, the density of silicone foam materials prepared in the current mature process can be as low as 0.16-0.20 g/cm3, and can be used for car seats, headrests and other components; while conventional silicone rubber foam materials ( Density 0.45 g/cm3) is widely used for gap filling in sealing, shock absorption and other parts.
2.Flame retardant properties of silicone foam
According to scientific experimental research data, silicone foam with added flame retardants has very good flame retardant properties, and the flame retardant grade can reach UL94-V0. When applied to electric vehicles, it can well reduce the risk of fire caused by combustion. question.
3.Electrical insulation properties of silicone foam
As the amount of physical filler increases, the volume resistivity and surface resistivity of silicone rubber show a decreasing trend, and the dielectric constant and dielectric loss factor generally show an increasing trend. It can be seen that adding physical fillers damages the electrical insulation properties of silicone rubber to a certain extent.
4.Application of silicone foam in electric vehicle industry
The battery core is the source of kinetic energy for pure electric vehicles. The safety hazards of the battery core seriously endanger the safety of the entire vehicle. When the battery core is working, it will generate a certain amount of heat and can produce a certain thermal expansion and contraction effect at different temperatures. , resulting in a certain expansion of the battery core, and long-term capacitive grid friction between the battery cores, which is likely to cause damage to the battery core and cause the rechargeable battery to be ineffective, and even uncontrollable in severe cases. In addition, when the output voltage of the battery pack reaches more than 200V, the battery case must be sealed and waterproof to avoid short circuit caused by water seepage. The waterproof grade of the battery case is required to reach IP67.
Silicone foam has high shrinkage reduction characteristics, which prevents deformation caused by thermal expansion and contraction of the battery Cell during the charging and discharging process. It has excellent durability, low shrinkage, and impact absorption. and flame retardancy (UL 94 V0 rating). At the same time, silica gel also has good waterproof properties and the following properties, so it is widely used in cache insulation and outer frame sealing of new energy batteries.
1. Under different temperatures, silicone foam has stable performance, and commercial sealing rings have stable performance.
2. Excellent waterproof sealing, no water seepage when the product is used outside.
3. The long-term shrinkage damage is small, and it has a certain ability to restrain shrinkage deformation.
4. Excellent flame retardant performance can effectively prevent risks caused by thermal effects during battery operation.
5. The thickness and strength can be designed according to different standards. The sealing ring must be well matched with the cover and have low internal stress, which can effectively prevent the sealing ring from bending and arching.
The working principle of thermally conductive silicone sheets for new energy vehicle lithium batteries: Because the temperature difference inside the battery pack is not controlled within 5°C, a thermally conductive silicone sheet needs to be attached to the top and bottom of the battery pack, and the thermally conductive silicone sheet will then guide the temperature to the outer aluminum shell. The temperature difference of the entire battery module is controlled within 5°C, which meets the requirements of battery pack design, thereby extending the service life of the battery pack and making the performance more stable during driving.
Between batteries and between batteries and pipes, filling thermally conductive silicone sheets with good electrical insulation and thermal conductivity can play the following roles:
1. Change the contact form between the battery and the heat dissipation pipe from line contact to surface contact;
2. Helps increase the temperature between single cells;
3. It is helpful to increase the overall heat capacity of the battery pack, thereby reducing the overall average temperature.
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