Why clear silicone keyboard/silicone phone case yellowing

Clear Silicone Rubber Keyboard or Clear Silicone Phone Case which made of clear silicone rubber will turn yellow after use for a period.

Why clear silicone turn yellow? 

This blog aims to discuss the reasons and the solutions.

1. Vulcanizing agent

A. The performance of vulcanizing agent is divided into common type and anti-yellow property. Its application range has the following two aspects:

●Common type non-anti-yellow vulcanizing agent, applied to some non-exposed silicone rubberproducts which can be used for dark color or low color requirements.

●Anti-yellow vulcanizing agent is applied to products that need to be exposed, lighter and vivid in color, and have higher color requirements.

The quality of vulcanizing agent is highly correlated with hydrogen-containing silicone oil. Dow Corning contains hydrogen silicone oil with hydrogen content above 1.6.

The acid value is below 1 which effect is better.

2.Processing

When the clear silicone rubber keyboard/silicone phone case is molding, the color of the clear silicone product turns yellow after molding. There are mainly problems:

●The mold temperature is too high.

●The curing time is too long.

●After secondary vulcanization.

3.Clear silicone rubber keyboard/silicone phone case raw material.

Sometimes we add anti-yellow vulcanizing agent to the silicone rubber material, but the clear silicone rubber keyboard still looks yellowish after molding. It may be that the yellowing resistance of the silicone rubber raw material is too bad. It is suggested to change the silicone rubber raw material directly.

Solutions:

1. Add anti-yellowing double 2.5 vulcanizing agent, which contains a high amount of hydrogen silicone oil, to improve the anti-yellowing effect of clear silicone rubber keyboard.

2. To use higher purity silica

3. Adding a silicon-magnesium nano-done enhancer can improve the absorption, whitening and yellowing of clear silicone rubber, and can improve the transparency of ordinary precipitated silicone to over 90%.

Conclusion: 

It is necessary to select the vulcanizing agent according to the requirements. In the process, the temperature of the mold and the vulcanization time of the product should be strictly controlled. The raw material should pay attention to the yellowing resistance of the raw material.

The phenomenon of silicone rubber keyboard turning yellow is the essence of ordinary silicone products. Generally, the yellowing phenomenon occurs after use for a long time, but the addition of anti-yellowing agent can achieve non-yellowing or the use food grade silicone rubber raw materials.

Xiamen Better Silicone Rubber Co.,ltd produce anti-yellowing clear silicone rubber keyboard, clear silicone rubber sealing, gasket, clear silicone rubber phone case and so on.

Welcome to send us desing drawing. Not only we can provide moldability analysis, manufacturability analysis based on your products, but also we provide design support.