New Energy Vehicle Sealing, Buffering, and Thermal Protection Material — Silicone Foam Rubber

Silicone foam rubber, also known as silicone foam or foamed silicone, is a porous, low-density, compressible elastomer made from raw materials such as silicone gum, fillers, vulcanization accelerators, and foaming agents, mixed uniformly and then processed under special conditions of high pressure and high temperature. It possesses the high elasticity of silicone rubber and the sound insulation and vibration damping properties of foam materials. It is widely used in various applications such as vibration reduction pads, sealing gaskets, sound absorption materials, insulation materials, and aviation thermal insulation materials. Based on the pore structure, silicone foam rubber can be classified into closed-cell, open-cell, and hybrid types.

Closed-cell silicone foam rubber has excellent shock absorption, sound insulation, heat insulation, flame retardancy, and other characteristics. It is mainly used in the automotive field for insulation foam pipes for automotive HVAC systems, automotive shock absorption, and foam silicone rubber sealing gaskets for new energy vehicle batteries. Many interior materials in today's automobiles, such as floors, ceilings, steering wheels, and car seats, are made of polyurethane foam materials. On the one hand, polyurethane foam materials have relatively mature technology and meet the required standards. On the other hand, polyurethane foam materials are cheaper. However, polyurethane foam materials have poor weather resistance, are flammable, and release a large amount of toxic gases harmful to humans during combustion. Therefore, with the promotion and increased awareness of silicone foam rubber materials, it is expected that silicone foam rubber materials will replace traditional polyurethane foam materials in the future.

Silicone thermal insulation is a type of silica gel prepared from raw materials such as alkali-free ultra-fine glass wool, room-temperature vulcanized silicone rubber, gas-phase method white carbon black, iron oxide, and hydroxyl silicone oil.

Silicone thermal insulation and buffering frame products have the functions of cushioning and thermal insulation and can be used in the field of thermal protection for lithium batteries in new energy vehicles.

Characteristics of silicone foam rubber:

1. Density: The density of silicone foam rubber is 1.17g/cm3. Through foam processing, the density of silicone foam rubber materials prepared by current mature processes can be as low as 0.16-0.20g/cm3, which can be used for automotive components such as car seats and headrests. Conventional silicone foam rubber materials (density of 0.45g/cm3) are widely used to fill gaps in sealing, shock absorption, and other parts.

2. Flame Retardancy: Scientific testing data shows that silicone foam rubber with flame retardants has excellent flame retardancy, and the flame retardancy level can reach UL94-V0. When applied in electric vehicles, it can effectively reduce problems caused by combustion.

3. Electrical Insulation Performance: With the increase in the amount of physical fillers, the volume resistivity and surface resistivity of silicone rubber tend to decrease, while the dielectric constant and dielectric loss factor tend to increase. It can be seen that the addition of physical fillers to some extent impairs the electrical insulation performance of silicone rubber.

Application of silicone foam rubber in the electric vehicle industry:

The battery cell is the power source of electric vehicles. The safety hazards of battery cells seriously endanger the safety of the entire vehicle. During operation, the battery cell generates heat, and under different temperatures, it undergoes thermal expansion and contraction, causing the cell to expand and long-term intercellular friction, potentially damaging the cell and rendering the charging battery ineffective. In severe cases, it may even lead to loss of control. In addition, when the battery pack output voltage exceeds 200V, it is required that the charging battery housing must be sealed and watertight to prevent water penetration causing circuit short-circuits. The waterproof rating of the charging battery housing should reach IP67.

Application of silicone foam rubber in the thermal insulation of new energy vehicle lithium batteries:

Silicone foam rubber has the characteristics of high compressibility, excellent durability, low shrinkage, shock absorption, and flame resistance (UL 94 V0 rating) during the charging and discharging process of batteries, thus achieving widespread applications in the thermal insulation and frame sealing of new energy battery cores.

1. At different temperatures, the performance of silicone foam rubber is stable, ensuring stable sealing ring performance.

2. Excellent waterproof sealing performance, no water penetration during outdoor use.

3. Minimal long-term shrinkage damage, with the ability to restrain shrinkage and deformation to a certain extent.

4. Excellent flame retardancy, effectively preventing risks caused by heat 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 housing, and low internal stress can effectively avoid bending and arching of the sealing ring.

The working principle of applying thermal conductive silicone film in new energy vehicle lithium batteries is that due to the uncontrolled temperature difference within the battery pack, a thermal conductive silicone film is attached to the top and bottom of the battery pack to guide heat to the outer aluminum shell, effectively controlling the temperature difference within the entire battery module to within 5°C. This extends the life of the battery pack and ensures stable performance during driving.