Why Polycarbonate Yellows in the Sun

Polycarbonate yellowing refers to the phenomenon where polycarbonate materials gradually change color over time, taking on a yellow or brownish tint. This discoloration occurs over the course of  several years and can affect the aesthetic appeal and optical properties of the material. The yellowing of polycarbonate is a common issue that occurs due to various environmental factors and exposure to ultraviolet (UV) radiation.

Factors that Contribute to Yellowing 

  • UV Radiation: One of the biggest reasons for the yellowing of polycarbonate is exposure to sunlight. This exposure results in oxidation which causes the polymer chains in the polycarbonate to break down, leading to a change in the material's color.
  • Heat: Combined with exposure to sunlight, high temperatures can also contribute to the breaking down of Polymers that causes discoloration.
  • Chemical Exposure: Certain chemicals and environmental pollutants can also contribute to the yellowing of polycarbonate. Exposure to harsh chemicals, such as cleaning agents or solvents, may cause the material to deteriorate and discolor.
  • Poor Quality Additives: If the polycarbonate contains impurities or low quality additives are used in the polycarbonate formulation, then this may also lead to discoloration. Environmental conditions may cause the impurities to undergo chemical reactions causing the material to discolor.

Mitigating or Preventing Yellowing 

  • UV Stabilizers: Manufacturers often incorporate UV stabilizers into polycarbonate formulations to enhance resistance to UV radiation. These stabilizers help protect the material from the harmful effects of sunlight and minimize yellowing.
  • Coatings: Applying UV-resistant coatings or films to polycarbonate surfaces can provide an additional layer of protection against UV radiation and help prolong the material's clarity.
  • Proper Maintenance: Avoid using abrasive or harsh cleaning agents on polycarbonate surfaces, as these can contribute to degradation. Regular cleaning with mild soaps and soft cloths can help maintain the material's appearance but make sure to rinse the material thoroughly in order to prevent any residue.
  • Storage: When not in use, store polycarbonate items indoors or in shaded areas to minimize exposure to UV radiation.

Ways to Clean Yellowed Polycarbonate 

There are several methods and products that individuals can try to rejuvenate and improve the appearance of yellowed polycarbonate surfaces. It's important to note that the success of these methods may vary depending on the severity of the yellowing and the specific conditions that caused it.

  • Polishing Compounds: Commercial polishing compounds specifically designed for plastics can be used to buff and polish yellowed polycarbonate surfaces. These compounds often contain fine abrasives that help remove the discolored layer, restoring clarity.
  • Baking Soda Paste: Create a paste by mixing baking soda with water, and gently rub it onto the yellowed polycarbonate surface using a soft cloth. Rinse thoroughly after application. Baking soda's mild abrasive properties can aid in removing surface discoloration.
  • Hydrogen Peroxide: Diluted hydrogen peroxide (mixed with water) can be applied to the yellowed polycarbonate using a soft cloth. Allow it to sit for some time before rinsing. This method is effective in breaking down certain types of discoloration.
  • Professional Restoration Kits: There are commercial restoration kits available that include specially formulated compounds and materials for restoring yellowed plastics. These kits may be more effective in addressing severe discoloration.

It's crucial to test any restoration method on a small, inconspicuous area before applying it to the entire surface to ensure that it doesn't cause further damage. Additionally, patience and gentle application are key, as aggressive methods may scratch or damage the polycarbonate. While these methods may improve the appearance of yellowed polycarbonate to some extent, they might not provide a permanent solution. In some cases, replacement of the polycarbonate component may be the most effective long-term solution.


While yellowing is a natural process for polycarbonate, taking preventive measures can significantly extend the material's lifespan and maintain its optical clarity. Advances in material science continue to improve the UV resistance of polycarbonate, leading to enhanced durability and reduced yellowing over time.

 Sources and Contributors 

  1. OpenAI. (2023). ChatGPT (Mar 14 version) [Large language model]. https://chat.openai.com/chat
  2. Excelite Plastics. (2023, July 26). Does Polycarbonate Yellow Over Time? Explained. Excelite Plastics. Retrieved January 10, 2024, from https://www.exceliteplas.com/en/blog/how-to-determine-polycarbonate-yellowing-index


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