Why do transparent silicone products turn yellow

Table of Contents


Transparent silicone products will normally not turned yellow after being stored for several years. However, sometimes during production, some newly released transparent silicone products will look yellow and seem to have changed color. Why do transparent silicone products turning yellow? Among many silicone products, transparent phone case are particularly obvious

Reasons why transparent silicone products turn yellow

The quality of the raw materials itself is too poor

Sometimes we add an anti-yellowing vulcanizing agent to the rubber, but the transparent clear silicone product still looks yellow after molding. It may be that the anti-yellowing ability of the raw material is too poor. For raw materials with poor yellowing resistance, the following suggestions are Direct material change.

Vulcanizing agent

1. The properties of vulcanizing agents are divided into ordinary type and yellowing resistance. Its application scope has the following two aspects:

2. Ordinary type non-anti-yellowing vulcanizing agent, used in some non-exposed silicone products that are dark in color or have low color requirements.

3. Anti-yellowing vulcanizing agents are used in products that need to be exposed, have lighter and brighter colors, and have higher color requirements.

External Factors and Their Impact

Natural Oils and Sweat

The human body naturally produces oils and sweat, substances that, when in contact with silicone phone cases, can accelerate the yellowing process. These organic compounds can be absorbed into the silicone material, where they undergo oxidation. As they oxidize, they can discolor the silicone, contributing to its yellowing. This effect is more pronounced in environments where the phone case is frequently handled or exposed to skin contact.

Chemical Exposure

Household cleaners, including dish soap and rubbing alcohol, are often used to clean silicone phone cases in an attempt to maintain their clarity. However, these substances can have the opposite effect. The chemicals in these cleaning agents can react with the silicone, exacerbating the yellowing process. Particularly, alcohol and other harsh chemicals can strip away protective coatings on the silicone in clear phone cases, making it even more susceptible to UV-induced photo-oxidation and discoloration.

Heat and Light Exposure

While UV light is a primary factor in the yellowing of silicone, general exposure to heat and light can also contribute to the process. Silicone products placed near windows or in hot environments are subjected to a constant barrage of light and heat, accelerating the degradation and yellowing process. Heat can enhance the chemical reactions that lead to yellowing, while visible and infrared light can contribute to the material’s deterioration over time.

Understanding these factors is crucial for anyone looking to maintain the appearance of their transparent silicone products. By recognizing the roles of UV radiation, natural oils, chemical exposure, and environmental conditions, users can take informed steps to protect their silicone items from yellowing.

Strategies to Mitigate Yellowing

Importance of Choosing Phone Cases Made from Quality Materials

The initial step in preventing yellowing lies in selecting a phone case crafted from high-grade silicone or thermoplastic polyurethane (TPU). These materials are engineered for durability and resistance to environmental factors that contribute to yellowing. Quality silicone products often incorporate advanced formulations designed to endure the rigors of daily use without compromising their appearance.

How Manufacturers’ Additives and Stabilizers Can Slow Down the Yellowing Process

Manufacturers can add UV stabilizers and antioxidants to the silicone material during the production process. These additives significantly slow down the degradation caused by UV light and oxygen, respectively. By opting for products that include these stabilizers, consumers can enjoy a clear, yellow-resistant phone case for longer periods. It’s beneficial to research and choose brands that highlight the durability and anti-yellowing features of their products.

Regular Maintenance and Care

Maintaining the condition of a silicone phone case extends beyond simple aesthetics; it’s about preserving the material’s integrity. Regular, gentle cleaning and careful handling of clear phone case can prevent the accumulation of substances that accelerate yellowing.

Cleaning Practices: Guidelines for Cleaning Phone Cases to Reduce Yellowing Risk

Mild Soap and Water: For routine cleaning, use a soft cloth, mild dish soap, and warm water to gently wipe the surface of the phone case. This method is effective in removing oils, sweat, and everyday grime.

Baking Soda Paste: For tougher stains or to brighten the case, a paste made from baking soda and water can be applied gently with a soft brush or cloth. Rinse thoroughly afterward.

Air Dry: Always allow the case to air dry completely before reattaching it to your phone to prevent moisture buildup, which could further degrade the material.


When transparent silicone products are molded, the main problems that cause the color of transparent silicone products to turn to yellow color after molding are:

1. The mold temperature is too high

2. The vulcanization time is too long,

3. After secondary sulfur addition

To sum up, the yellowing of silica gel is a chemical reaction caused by improper operation or material selection during the production process. Using bleach to bleach the surface layer will not help the natural process. As a silicone manufacturer, we must strictly carry out every process to provide customers with high-quality products.

Although silicone products have excellent weather resistance and anti-aging properties. However, sometimes freshly baked silicone products still appear yellow. In order to avoid this situation, the vulcanizing agent must be selected according to the requirements. In terms of process, the temperature of the mold and the vulcanization time of the product must be strictly controlled. In terms of raw material degradation of materials, the yellowing resistance of the raw materials must be paid attention to.

How to deal with yellowing of silicone rubber

1. Use bleach: Soak silicone rubber products in white bleach diluent, take them out and dry them after 30 minutes.

2. Use ultraviolet germicidal lamp: Long-term exposure to ultraviolet germicidal lamp can effectively remove yellow spots on the surface of silicone rubber.

3. Use a wiping agent: Choose a suitable wiping agent and gently wipe the surface of the silicone rubber product to remove the yellow spots on the silicone rubber and play a protective role.

4. Use silicone rubber maintenance agent: Choosing the appropriate silicone rubber maintenance agent can restore the original color of silicone rubber products and have a certain protective effect.


Liquid silicone, mold silicone rubber raw materials, and silicone raw materials are stored at room temperature for 6 months. During use, water, impurities, organotin catalysts of condensed silicone rubber, acids, alkali and other organic substances containing sulfur, phosphorus, and nitrogen may affect the rubber’s properties. Curing, these impurities should not be mixed during use.

For silicone product factories, silicone molds are very important. Based on the actual situation of adverse phenomena in silicone molds, we conduct detailed analysis and research to find out the causes of mold defects in silicone products and propose remedial methods.

During the production process, it is necessary to promptly select the characteristics of the silicone material, analyze the amount of silicone oil, and repair the mold to eliminate errors after discovering problems.

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