What reason is silica gel product yellowing

Since transparent silica gel products are transparent how possible yellow, yellow can be transparent, what reason is that caused? Is it oxidation? Normal transparent silica gel products are put for several years will not yellow, but sometimes we are in production, some transparent silica gel products just out of the oven will yellow, the transparent silica gel products why yellow? The main problem lies in the following aspects:

I. vulcanizing agent

1 vulcanizing agent performance is divided into common type and yellow resistance. Its application scope has the following two aspects:

2. Common type of non-yellow vulcanizing agent, used in some can be used for color is dark or the color is not high requirements of non-exposed silica gel products.

3. Anti-yellow vulcanizing agent should be used in products that need to be exposed, light and bright color, and have high requirements for color. The quality of vulcanizing agent is highly correlated with hydrogen silicone oil. Dow Corning contains hydrogen silicone oil with hydrogen value above 1.6. Acid value below 1, the effect is better.

Two. The process

Transparent silica gel products in the forming, leading to transparent silica gel products in the forming after the color of yellow main problems are:

1. The mold temperature is too high;

2. Too long curing time;

3. After adding sulfur twice.

The raw material itself is of poor quality

Sometimes we add anti-yellow vulcanizing agent in the rubber compound, but the transparent silica gel product still looks yellow after molding. It may be that the anti-yellow ability of the raw material is too poor. The raw material is suggested to be directly refueling.

Conclusion: Although silicone products have excellent weather resistance and aging resistance. But sometimes the silicone products that have just come out of the oven turn yellow. In order to avoid this situation, according to the requirements of the selection of vulcanizing agent, process to strictly control the temperature of the mold and product vulcanization time, raw materials should pay attention to the yellow resistance of raw materials.