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4Common problem

Silicone products manufacturers introduce silicone products yellowing what is the reason?

The rubber products will not turn yellow after a few years of normal operation, but sometimes in the production, some of the transparent silicone products that have just been baked appear yellowish and seem to have changed color. Why do silicone products yellow?

First, the vulcanizing agent:

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

2. Ordinary non-anti-yellow vulcanizing agent, applied to some non-exposed silicone products that can be used for darker colors or less demanding colors.

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

Second, the process:

When the silicone product is molded, the color of the silicone product turns yellow after molding. There are mainly problems:

1. The mold temperature is too high;

2. The curing time is too long;

3. After secondary vulcanization

Third, the quality of the raw materials themselves is too poor:

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

There are several reasons for the yellowing of silicone rubber:

The first is the production of silicone rubber raw rubber and the trace metal elements and NO contained in the additive;

Second, the dialkyl peroxide decomposes to produce acetone, resulting in condensation and dehydration of alpha hydroxybutanal to form a conjugated compound;

Third, the pH value of silica affects the yellowing of silicone rubber. When the pH of white carbon black is acidic, the silicone rubber can be significantly yellowed. The degree of yellowing is inversely related to the pH value. When the pH is less than 5. 5 The inverse proportional relationship is more obvious.

How to improve the yellowing of silicone rubber:

1. Adding a cream-like double 2,5 vulcanizing agent with anti-yellowing properties, and containing a high amount of hydrogen silicone oil, the silicone rubber has a significant improvement in anti-yellowing effect;

2. Choose to use a relatively pure white carbon black;

3. Adding a silicon-magnesium nano-adialysis agent can improve the advantages of easy absorption, whitening and yellowing of the transparent silica gel, and can improve the transparency of the ordinary precipitation gel to over 90%.

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