How to improve the transparency of rubber compound?

The transparency of key compounds is directly related to the transparency of silica, so silica with better transparency can be selected.

In terms of formula and process, the transparency of the rubber compound is not good, indicating that the surface hydroxyl treatment of the white carbon black is insufficient, which affects the transparency of the rubber compound. In other words, the hydroxyl silicone oil we added is not enough to treat the hydroxyl groups on the surface of silica black, indicating that there are some pseudo hydroxyl groups in the hydroxyl silicone oil, and some substances that did not participate in the reaction were removed during vacuuming or heat treatment. At the same time, it also shows that the combination of white carbon black molecules and raw rubber molecules is incomplete or the combination time is not enough, and can be adjusted from the process. Raw rubber and silica are first mixed at room temperature, and the hydroxyl groups on the surface of the silica are treated with a combination of hydroxyl silicone oil and alkoxysilane in the formula, and then cured at 30~40°C for about 8 hours, and then evacuated. This will Improve the transparency of the rubber compound. At the same time, in addition to physical properties, key glue should also control key force and fatigue life. We can use instruments to test and control its indicators within a certain range.

How to improve the structure of existing rubber compounds?

Structured rubber compound is a rubber compound made by mixing hydrophilic silica and raw rubber. During the storage process, the rubber compound gradually hardens, the plasticity decreases, and the process performance of tempering molding is gradually lost. The main reason for the formation of structural rubber compounds is that the silicone hydroxyl groups on the surface of the silica interact with the silica-oxygen bonds in the raw rubber molecules or the terminal hydroxyl groups in the raw rubber molecules to produce hydrogen bonds or even chemical bonding, turning the linear polysiloxane into The solid structure of the pseudo-crosslinked semi-elastomer reduces the solubility of the rubber compound and increases the gel content.

Generally speaking, the plasticity of a compound can be restored by backmixing, the length of which depends on the structural severity of the compound. In order to reduce the hydrogen bonding of the compound and the structural degree of the compound, structure control agents such as hydroxyl silicone oil or alkoxysilane can be added, and an appropriate amount of dimethyl silicone oil can be added to adjust the flow properties of the compound. Adding too much hydroxyl silicone oil to the rubber will result in a sticky feel and slow vulcanization speed, so it is necessary to find a suitable balance point that can control each type of rubber within the appropriate plasticity value range. Low or high plasticity will have an impact on the later processing of the product. If the plasticity is low, the roller will stick during processing, and a sticky film may appear during product production. If the plasticity value is too high, the structure and fluidity of the rubber will be poor, and the product may lack glue or have flow marks.

It can also be improved from the rubber compound production process. We now use a one-step method to produce mixed rubber, so that the combination of silica and raw rubber is incomplete. Although there are no obvious abnormalities on the surface, sometimes small white spots are observed in the rubber compound, which can be produced through the process of mixing (normal temperature)-vulcanization-internal mixing, thereby improving the bonding degree between silica and raw rubber and improving Mix structure.