Does Polycarbonate Turn Yellow? Complete UV Protection Guide

Understanding Polycarbonate Yellowing

Polycarbonate yellowing is a gradual discoloration process where clear polycarbonate sheets develop a yellowish or brownish tint. This degradation affects both the aesthetic appeal and functional performance of the material, reducing light transmission and compromising structural integrity over time.

Why Does Polycarbonate Turn Yellow?

The primary causes of polycarbonate yellowing include:

UV Radiation Exposure

Ultraviolet light from sunlight is the leading cause of polycarbonate yellowing. When UV rays penetrate the material, they break down polymer chains at the molecular level, creating degradation byproducts that absorb yellow wavelengths of visible light. This degradation occurs approximately 25 micrometers deep into the surface.

Oxidation Process

Polycarbonate reacts with oxygen in the air, particularly when heat accelerates the process. This chemical reaction degrades the molecular structure, leading to discoloration and reduced mechanical strength. Higher temperatures significantly speed up oxidation, compounding UV exposure effects.

Heat and Temperature

Elevated temperatures promote oxidation by causing polymer chains to react more rapidly with oxygen. In high-temperature environments—whether from prolonged sun exposure in Canadian summers or industrial settings—yellowing accelerates dramatically.

Chemical Exposure

Harsh chemicals such as aggressive cleaning agents, solvents, or environmental pollutants can strip away UV-resistant coatings or protective surface layers. Alkaline cleaners and strong solvents erode the surface, reducing UV blocking capability and accelerating discoloration.

Poor Quality Materials

Polycarbonate sheets manufactured with impurities or low-quality additives are more susceptible to yellowing. Environmental conditions can trigger chemical reactions with these impurities, causing premature discoloration.

UV Protection Technology for Polycarbonate

Modern polycarbonate sheets incorporate advanced UV protection technologies to prevent yellowing:

Co-Extrusion UV Protection

The most effective method involves co-extruding UV-protective layers (50-80 micrometers thick) directly into the polycarbonate during manufacturing. This integrated protection blocks 99% of harmful UV rays and provides superior weather resistance compared to surface coatings.

The UV protection layer degrades at approximately 5 micrometers per year, providing long-lasting protection when manufactured with sufficient thickness.

Surface Coating UV Protection

Less durable than co-extrusion, surface coatings can be stripped by harsh chemicals or weather exposure. These coatings offer shorter lifespans and reduced effectiveness compared to co-extruded protection.

Single vs. Double-Sided UV Protection

• Single-sided UV coating: Protects the outer surface exposed to sunlight (most common for roofing, greenhouses)
• Double-sided UV coating: Protects both surfaces (ideal for applications with dual exposure)

The UV-protected side is typically marked with branded film during installation and should face the sun.

Can Yellowed Polycarbonate Be Restored?

Yellowing caused by UV degradation is largely irreversible because it results from permanent structural changes in the polymer chains. However, some surface-level restoration methods may provide temporary improvement:

Polishing Compounds

Commercial polishing compounds designed for plastics can remove the discolored surface layer. These compounds contain fine abrasives that buff away oxidized material, potentially restoring some clarity. Success depends on the depth of UV penetration.

Baking Soda Treatment

Create a paste with baking soda and water, gently rubbing it onto yellowed surfaces with a soft cloth. The mild abrasive properties may help remove surface discoloration. Rinse thoroughly after application.

Professional Restoration

For valuable installations, professional restoration services using specialized equipment and compounds may achieve better results than DIY methods.

Important Note: Restoration is temporary and will not prevent future yellowing without proper UV protection. It's better to start with quality UV-protected sheets from Plastics Canada.

Polycarbonate Applications Vulnerable to Yellowing

Understanding which applications are most at risk helps you make informed purchasing decisions:

High-Risk Applications (require premium UV protection):

• Greenhouse panels and roofing
• Pergola covers and patio roofs
• Outdoor skylights
• Carport shelters
• Pool enclosures
• Commercial glazing
• Security barriers (outdoor)

Moderate-Risk Applications:

• Interior partition walls
• Machine guards (indoor)
• Indoor signage
• Display cases

Low-Risk Applications:

• Indoor architectural features
• Interior design elements
• Protected installations

All outdoor applications should use polycarbonate with verified UV protection like the sheets available at Plastics Canada.

Conclusion

Polycarbonate yellowing is preventable with proper material selection and care. By choosing UV-protected polycarbonate sheets from Plastics Canada, you ensure your investment maintains clarity and performance for 10-15 years—even in Canadian climates ranging from coastal BC to prairie winters.

Whether you're building a greenhouse in Ontario, installing a pergola cover in BC, or creating safety barriers in Alberta, start with quality materials that resist yellowing from day one. Our premium Lexan and Makrolon polycarbonate sheets offer the UV protection you need for long-lasting clarity.

Ready to start your project? Shop Polycarbonate Sheets or contact our team for personalized recommendations.