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Plastic Yellowing: Causes, Prevention, and Restoration

Plastic is a versatile material that is used in a wide range of applications. However, over time, some types of plastic can develop a yellowish discoloration, which can be unsightly and reduce the quality of the material. In this post, we'll take a closer look at plastic yellowing, its causes, and what you can do to prevent and restore it.

What is Plastic Yellowing?

Plastic yellowing, also known as plastic discoloration, is a process where certain types of plastic materials develop a yellowish discoloration over time. This discoloration can be caused by a variety of factors, such as exposure to UV light, heat, chemical exposure, and the quality of the plastic or additives used in the material. Yellowed plastic can be unsightly and may affect the quality of the material, so it's important to understand the causes of plastic yellowing and how to prevent it.

Types of Plastic that are Prone to Yellowing

Some types of plastic are more prone to yellowing than others. The most common plastics that are prone to yellowing include:

• Polycarbonate(also called PC): This type of plastic is often used in applications such as automotive parts, electronic devices, and eyewear. Polycarbonate is prone to yellowing when exposed to UV light, heat, and certain chemicals.

• ABS: ABS plastic is commonly used in automotive parts, toys, and electronic housings. It is known to yellow over time when exposed to UV light.

• Acrylic(also called PMMA): Acrylic plastic is commonly used in signage, aquariums, and home decor. It can yellow when exposed to UV light and high temperatures.

While these are the most common types of plastic that are prone to yellowing, it's important to note that any plastic material can yellow over time if exposed to certain environmental factors.

How Long will Plactic Turn Yellow?

In general, it is difficult to predict exactly how long it will take for plastic to turn yellow. The length of time it takes for plastic to turn yellow can vary depending on several factors such as the type of plastic, quality of the plastic, exposure to UV light and heat, and other environmental factors.

Some types of plastics, such as low-quality polypropylene, can begin to show signs of yellowing after just a few months of exposure to UV light and heat. Higher quality acrylic materials, such as those made from pure acrylic, tend to be more resistant to yellowing than lower quality materials. However, even high-quality acrylic can turn yellow over time if it is exposed to enough UV light and heat. Factors such as exposure to direct sunlight, extreme temperatures, and chemical exposure can all accelerate the yellowing process. However, proper care and maintenance of plastic materials, such as avoiding exposure to UV light and heat, can help prevent yellowing and extend the lifespan of the material.

Overall, the length of time it takes for plastic to turn yellow can vary greatly depending on the specific type and quality of the plastic, as well as the environmental factors it is exposed to.

Factors that Contribute to Plastic Yellowing

Several factors can contribute to plastic yellowing. Some of the most common factors include:

• UV Light Exposure: One of the main causes of plastic yellowing is exposure to UV light, which can break down the chemical bonds in the plastic and cause it to discolor over time.

• Heat Exposure: High temperatures can also cause plastic to yellow. This is because heat can accelerate the breakdown of the plastic, leading to discoloration.

• Chemical Exposure: Exposure to certain chemicals, such as chlorine or ammonia, can cause plastic to yellow. This is because the chemicals can react with the plastic and alter its color.

• Poor Quality Plastic: Poor quality plastic or additives used in the material can make it more prone to yellowing. This is because the plastic may not be able to withstand environmental factors as well as higher quality materials.

It's important to note that plastic yellowing is often a combination of several environmental factors. For example, exposure to both UV light and heat can cause plastic to yellow more quickly than either factor alone.

Acrylic and Plycarbonate, who is easier to turn yellow for Lighting Application? 

For lighting applications, both acrylic(PMMA) and polycarbonate can be used as lens diffusers or covers for LED lights, but acrylic is generally considered to be the better option in terms of resistance to yellowing.

Acrylic(PMMA) has a higher resistance to UV light than polycarbonate, which can cause yellowing over time. This makes it more suitable for outdoor lighting applications or areas where the lighting may be exposed to direct sunlight.

Overall, if you are looking for a plastic material for lighting applications that is less likely to yellow over time, Acrylic(PMMA) may be the better choice due to its higher resistance to UV light.

Preventing Plastic Yellowing

Preventing plastic yellowing can help extend the life of plastic products and keep them looking their best. Here are some tips to help prevent plastic yellowing:

• UV Protection: One of the most effective ways to prevent plastic yellowing is to protect the plastic from UV light. This can be done by using UV-resistant coatings or films, or by storing the plastic in a location that is not exposed to direct sunlight.

• Temperature Control: Controlling the temperature around plastic products can also help prevent yellowing. Avoid exposing plastic products to high temperatures, such as in direct sunlight or near heat sources like ovens or radiators.

• Proper Cleaning: Proper cleaning of plastic products can also help prevent yellowing. Avoid using harsh chemicals that can damage the plastic, and use a mild detergent and soft cloth to clean the surface.

• Quality Materials: Using high-quality plastic materials and additives can help prevent yellowing. Choose materials that are designed to resist UV light and heat exposure.

• Regular Maintenance: Regularly inspecting and maintaining plastic products can help prevent yellowing. This includes cleaning and protecting the plastic, as well as monitoring for signs of yellowing or other damage.

By following these tips, you can help prevent plastic yellowing and keep your plastic products looking their best for years to come.

Restoring Yellowed Plastic

If your plastic has already turned yellow, there are several methods for restoring it to its original color. Here are some options:

• Cleaning: Sometimes yellowing can be caused by surface dirt or grime. Cleaning the plastic with a mild detergent and soft cloth may be enough to remove the discoloration.

• Bleaching: Bleaching the plastic with a solution of hydrogen peroxide and water can also help restore its original color. However, this method should be used with caution, as it can weaken the plastic and cause it to become brittle over time.

• Sanding and Polishing: Sanding the surface of the plastic and then polishing it with a plastic restorer can also help remove yellowing. This method is best suited for hard plastics, such as polycarbonate, and may not be effective on softer materials.

• Replacement: If the plastic is severely yellowed or damaged, it may be necessary to replace it with a new piece. In some cases, replacement may be more cost-effective than trying to restore the plastic.

It's important to note that not all methods of restoring yellowed plastic are effective for all types of plastic. It's important to research the specific type of plastic you are working with and consult with a professional before attempting any restoration methods.

Conclusion

Plastic yellowing can be a frustrating problem, but with the right knowledge and care, it can be prevented and reversed. Understanding the causes of plastic yellowing, choosing the right type of plastic, and taking proper care of your plastic materials can help to keep them looking their best for longer. Alpha offering light diffuser profile and optical lens in PC and PMMA material, all of them are UV resistance, especially the PMMA could be exposured to outdoor, if you are looking for lampshade for your luminaire, contact us today to get more details.