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 rubber compound is not good, which indicates that the surface hydroxyl treatment of silica is not sufficient, affecting the transparency of rubber compound. That is to say, the hydroxyl silicone oil we added is not enough to treat the hydroxyl on the surface of silica, indicating that there are some pseudo hydroxyl groups in the hydroxyl silicone oil, and some substances that do not participate in the reaction are removed during vacuum or heat treatment. At the same time, it also shows that the combination of silica molecules and raw rubber molecules is not complete or the combination time is not enough, which can be adjusted from the process. The raw rubber and white carbon black are mixed at room temperature, and the hydroxyl group on the surface of white carbon black is treated with the combination of hydroxyl silicone oil and alkoxysilane in the formula, and then solidified at 30~40 ℃ for about 8 hours, and then vacuumized, which will improve the transparency of the mixed rubber. At the same time, in addition to physical properties, the key adhesive should also control the 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 the existing rubber compound?

Structured rubber compound is made of hydrophilic silica mixed with raw rubber, which gradually hardens, decreases plasticity and gradually loses the technological properties of tempering molding during storage. The main reason for the formation of structural rubber compounds is that the silicon hydroxyl group on the surface of silica interacts with the silicon oxygen bond in the raw rubber molecule or the terminal hydroxyl group in the raw rubber molecule to produce hydrogen bonds, or even chemical bonding, which changes the linear polysiloxane into the solid structure of the pseudo crosslinked semi elastomer, reduces the solubility of rubber compounds, and increases the gel content.

In general, the plasticity of the compound can be restored by backmixing, and the length of backmixing time depends on the structural severity of the compound. In order to reduce the hydrogen bond of the compound and the structural degree of the compound, structure control agents such as hydroxy silicone oil or alkoxysilane can be added, and an appropriate amount of dimethyl silicone oil can be added to adjust the flow performance of the compound. Adding too much hydroxy silicone oil into the rubber compound will lead to sticky feeling and slow curing speed. Therefore, it is necessary to find a proper balance point to control each type of rubber compound within the appropriate plastic value range. Low or high plasticity will affect the later processing of products. If the plasticity is low, the roll will stick during the processing, and the film may appear during the production process. If the plasticity value is too high, the structure and fluidity of the rubber compound will be poor, and the product may lack of glue or flow marks.

It can also be improved from the process of rubber mixing production. We now use one-step method to produce rubber blend, which makes the combination of silica and raw rubber incomplete. Although no obvious abnormality can be seen on the surface, small white spots in the rubber can sometimes be observed, which can be produced through the process of mixing (normal temperature) - vulcanization - internal mixing, so as to improve the binding degree of silica and raw rubber and improve the structure of rubber compound.