why do tpu phone case turn yellow


Why do TPU Phone Cases Turn Yellow?


Phone cases are an essential accessory for most smartphone users, ensuring protection against scratches, impact, and daily wear. Among various types of phone cases, those made of Thermoplastic Polyurethane (TPU) have gained popularity due to their durability and flexibility. However, many TPU phone case users have observed a common issue - yellowing over time. This phenomenon has left many wondering why TPU phone cases turn yellow and how to prevent or reverse this discoloration. In this article, we delve into the factors causing yellowing and provide practical tips to maintain the appearance and longevity of your TPU phone case.

I. Understanding TPU:

Thermoplastic Polyurethane (TPU) is a synthetic material widely used in protective phone cases. It is a hybrid of rubber and plastic, offering excellent shock absorption and flexibility. TPU is known for its resistance to oil, grease, and abrasion, making it a reliable choice for phone case manufacturing. While inherently transparent, TPU can become yellowed or discolored over time under certain conditions.

II. Exposure to UV Radiation:

One of the primary reasons TPU phone cases turn yellow is prolonged exposure to ultraviolet (UV) radiation. UV rays emitted by the sun or artificial sources can break down the molecular structure of TPU materials, causing discoloration and deterioration. This change in color is most noticeable in clear or transparent TPU cases.

III. Oxidation and Air Pollution:

Besides UV radiation, TPU phone cases can also be affected by oxidation and air pollution. Oxygen molecules in the air can react with the TPU surface, resulting in a chemical change known as oxidation. This process can gradually alter the appearance of the TPU, leading to a yellowish hue. Air pollution, particularly in highly polluted areas, can accelerate the oxidation process, making TPU phone cases more susceptible to discoloration.

IV. Reactions with Heat and Humidity:

High temperatures can influence the longevity of TPU phone cases. When exposed to heat for extended periods, TPU can undergo thermal degradation, causing yellowing and loss of transparency. Similarly, high humidity levels can contribute to discoloration due to the absorption of moisture by the TPU material. Therefore, if you frequently use your phone in hot and humid climates, your TPU case might be more prone to turning yellow.

V. Inadequate Cleaning and Maintenance:

Improper cleaning and maintenance practices can also impact the appearance of TPU phone cases. Accumulated dirt, oils, and other contaminants on the surface can leave residues that gradually lead to discoloration over time. Failure to clean your TPU case regularly can accelerate the yellowing process and make it harder to restore the original color.

Maintaining the Appearance and Longevity of TPU Phone Cases:

1. Minimize UV Exposure:

To prevent yellowing, minimize your TPU phone case's exposure to direct sunlight and artificial UV sources. When not in use, keep your phone stored in a shaded area or a protective sleeve. Additionally, avoid placing the phone near windows or other UV-emitting light sources for extended periods.

2. Protective Coatings:

Consider applying a protective coating to your TPU phone case. Certain products, such as UV-resistant sprays or clear coatings, can provide an extra layer of protection against UV radiation, oxidation, and discoloration. These coatings create a barrier that prevents the environmental factors from directly affecting the TPU material.

3. Regular Cleaning:

Maintain the appearance of your TPU phone case by cleaning it regularly. Use a mild soap or detergent and warm water to hand wash the case. Gently scrub the surface with a soft cloth or sponge to remove dirt and oils. Avoid using harsh chemicals, abrasive materials, or excessive force during cleaning as they may damage the TPU material.

4. Avoid Extreme Environments:

Try to avoid exposing your TPU phone case to extreme temperatures, such as leaving it in a parked car on a hot day. Similarly, keep your phone away from excessive moisture or humid environments, such as bathrooms, saunas, or near water bodies. By avoiding extreme conditions, you can prolong the lifespan of your TPU phone case and maintain its appearance.

5. Consider Darker or Opaque Cases:

If you are concerned about yellowing, opt for TPU phone cases with darker or opaque colors instead of clear or transparent options. Darker cases are less likely to show discoloration, making them a practical choice if yellowing is a recurring issue for you.


While TPU phone cases offer excellent protection and flexibility, they can turn yellow over time due to various factors such as UV exposure, oxidation, heat, humidity, and inadequate cleaning. By understanding these reasons and following the maintenance tips provided, you can prolong the lifespan of your TPU phone case and maintain its original appearance. Remember, prevention and regular care are key to keeping your TPU case looking clean, clear, and visually appealing for an extended period.


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