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How to Test and Adjust the Hardness of Silicone Rubber Mixing Raw Materials?

1. How to test the hardness of silicone rubber mixing raw materials?

Many people mistakenly think that testing the hardness of silicone rubber mixing raw materials is only measured on the raw materials with a durometer. This understanding is wrong.

If we want to test the hardness of silicone rubber mixing raw materials, we need to add vulcanizing agent through silicone rubber mixing, and then put the material into a designated mold and undergo high temperature vulcanization to obtain a hardness block.

After the hardness block is cooled, it is obtained by pressing the hardness tester hard. To test the hardness, it is necessary to make a hardness block of different thickness and repeat the test to obtain the accurate material hardness.

Many manufacturers of silicone rubber products pass the hardness test on their own products. In fact, this practice is not correct, because different silicone rubber products have different shapes and uneven surfaces. After the test, there is a large error in the actual hardness. The correct approach should be to make hardness blocks for standardized testing.

Ⅱ. How to adjust the hardness of silicone rubber mixing?

Silicone rubber mixing manufacturers generally standardize production with a unit spacing of 10 degrees of hardness when producing silicone raw materials, such as 30-degree silicone, 40-degree silicone, 50-degree silicone, and so on.

So if we want to make a silicone rubber compounding raw material with a specified hardness, how should we prepare it?

Most silicone rubber products have their own specific standard hardness range. We need to configure the hardness according to the environment and conditions of the silicone rubber products themselves.

For example, the hardness of silicone rubber products is about 45 degrees, so how do we prepare 45 degrees of silicone raw materials? It is very simple, we only need to take half of the 40-degree silica gel raw material and the 50-degree silica gel raw material and mix them evenly in the open mill to obtain the 45-degree silica gel raw material.

In addition, we can also make 45-degree silica gel raw materials by adding and mixing 40-degree silica gel and 60-degree silica gel in a ratio of 3:1.

In fact, the mixing hardness of silicone rubber is very simple. We only need to understand the binary linear equation for accurate calculation to obtain any desired hardness.

For example, 38-degree silica gel raw materials, 57-degree silica gel raw materials, 63-degree silica gel raw materials, etc., can be accurately calculated in this way.

Of course, the minimum modulation hardness shall not be lower than the hardness of the existing silica gel raw materials, and the maximum shall not be higher than that of the existing silica gel raw materials. If you want low-hardness silicone or high-hardness silicone, you need to contact the silicone rubber compounding manufacturer for production customization.

In addition, when adjusting the hardness, it is best to use two kinds of silica gel with similar original hardness. For example, when preparing 45-degree silica gel raw materials, the quality of 40-degree and 50-degree silica gel raw materials for neutralization and modulation is better than that of 40-degree and 60-degree silica gel raw materials.

The smaller the difference in softness and hardness, the better the quality of the obtained silica gel raw material. Of course, if you still want better quality silicone raw materials, you can contact the silicone rubber compounding factory for customized production, and you do not need to adjust the hardness by artificial methods such as an open mill.

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