Why Does White Silicone Sealant Turn Yellow? Experts Explain The Causes And Solutions

White silicone sealant is widely used in construction, particularly for aluminum doors, windows, and glass curtain walls, due to its excellent sealing and weather-resistant properties. However, many users have reported that white silicone sealant gradually turns yellow over time, affecting both aesthetics and performance. Industry experts have analyzed the main reasons behind this phenomenon and provided solutions to mitigate the issue.

Key Causes of Yellowing

1. UV Exposure and Environmental Factors
   Prolonged exposure to ultraviolet (UV) rays accelerates oxidation, leading to yellowing. Additionally, acidic or alkaline substances (e.g., cleaning agents, cement) can react with the sealant, causing discoloration 12.

2. Incompatible Materials
   When silicone sealant comes into contact with oil-filled rubber materials (e.g., EPDM rubber strips), the oils can migrate to the surface under sunlight, causing yellow stains. This is irreversible and requires reapplication of the sealant 27.

3. Low-Quality Sealant
   Some manufacturers use inferior raw materials, such as recycled silicone or excessive fillers, which degrade faster under heat and UV exposure, leading to yellowing and cracking 25.

4. Chemical Reactions
   Aminosilane-based additives in neutral silicone sealants can oxidize over time, forming yellow compounds. Additionally, acidic cleaning agents can react with calcium carbonate in the sealant, leaving spots 35.

5. Improper Application
   Uneven application, insufficient thickness, or contamination (e.g., dust, oil) during installation can accelerate aging and discoloration 1.

How to Prevent Yellowing

• Choose High-Quality Sealant: Opt for UV-resistant, weatherproof silicone sealants from reputable brands.

• Avoid Direct Sunlight: Use protective coatings or select darker-colored sealants for sun-exposed areas 26.

• Ensure Compatibility: Test sealant with adjacent materials (e.g., rubber strips) before full application 2.

• Proper Maintenance: Regularly inspect and clean the sealant, avoiding harsh chemicals 1.

For severe yellowing, experts recommend removing the old sealant and reapplying a compatible, high-grade product. By addressing these factors, users can extend the lifespan and maintain the appearance of silicone sealant in construction projects.