Application of Silicone on Car Lights

As an essential component of automobiles, headlights play an important role in night illumination, driving signals, fog prevention, and turn signals, ensuring safe driving. In the production of automotive headlights, sealant must be used to seal the light reflector to the casing.

When bonding headlights, the sealant needs to withstand the heat emitted by the light bulb and maintain its bonding and sealing performance without releasing organic gases that cause fog or turning yellow and affecting the appearance under high-temperature conditions. Additionally, it needs to have good weather resistance against aging and cracking of the bonding layer under exposure to UV radiation from sunlight. Finally, the sealant needs to resist long-term erosion from water vapor and rainwater and maintain its sealing performance.

Currently, the sealants mainly used in automotive headlights are hot melt butyl sealants, hot reactive polyurethane hot melt adhesives, and organic silicone sealants. The use of ordinary hot melt adhesives in headlight sealing often results in problems such as water leakage, cracked bonding layers, poor bonding strength, and fogging, which seriously affect driving safety. In contrast, organic auto silicone sealants are widely used in automotive sealing due to their unique molecular structure, which provides excellent bonding, high and low-temperature resistance, weather resistance, hydrophobicity, outstanding electrical performance, and chemical corrosion resistance.

Good bonding of auto silicone sealants

In the production of headlights, most materials are plastics. The materials for making casings include ABS, PC, PP, and the materials for making reflectors have been changed from traditional glass to PC materials widely used today. Good bonding of car silicone sealants ensures the airtightness of headlights and prevents them from falling off. Poor bonding performance can lead to problems such as water leakage, which greatly reduces the service life of headlights.

High-temperature resistance of auto silicone sealants

During long-distance driving, headlights maintain high temperatures, and this heat is transferred to the sealant, which can damage the bonding performance and cause the sealant to fail. Special environmental requirements demand that the sealant has excellent high-temperature resistance. After curing, the tensile strength, elongation at break, and shear strength of organic silicone sealants were tested after baking samples at 150℃ for 24 hours.

High and low-temperature cycle resistance of auto silicone sealants

When automobiles drive in cold regions, the temperature inside the headlights increases with time, and the sealant gradually rises from the low temperature below zero to high temperature with the increase of temperature. After stopping, the temperature of the sealant drops slowly to outdoor temperature. To test the high and low-temperature cycle resistance of the sealant, strict testing conditions accelerate the aging of the adhesive body. After 1000 hours of high and low-temperature cycles, the organic car silicone sealant showed no cracking or delamination in appearance. The excellent resistance to changes in temperature ensures the normal operation of headlights in harsh low-temperature areas such as Mohe, Siberia, and Northern Europe.

UV resistance of auto silicone sealants

Automobiles are used outdoors for a long time. To ensure that the service life of headlights is extended, the sealant needs to have excellent UV resistance. That is, the highest-energy ultraviolet radiation reaching the earth's surface cannot break the main chain structure of organic silicon, ensuring its excellent UV resistance. This performance has been verified through corresponding tests. After 2000 hours of UV aging test, the appearance of the car silicone sealant showed no apparent changes.