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Causes and solutions of several common problems of silica gel mixing rubber

  • 09-15-2022

Common solutions of silica gel mixing rubber:

The factors and solutions affecting the resilience and vulcanization rate of silica gel mix can be carried out from the following aspects.

The ethylene content in the silica gel mix is not enough, or the distribution of the ethylene content of the raw rubber itself is not uniform, and the sulfur point can not be reached when curing, the curing speed is longer, the curing is not sufficient, and the elasticity of the mix is worse. By improving the overall vinyl content of rubber, adding an appropriate amount of hydrogen-containing silicone oil in the formula, reducing the use of filler, improve the rubber content, can solve the poor resilience, slow curing speed; Drawing deformation of slurry can be controlled by using different types of raw glue with ethylene content and a small amount of high ethylene raw glue. It is necessary to find a better balance in the formula to avoid the brittle condition of the slurry and improve the elasticity of the slurry.

The acid of silica gel is also an important factor of poor elasticity and slow vulcanization rate of rubber. Because the white carbon black itself is acidic, so the added structure control agent is mostly acidic, so that the mixed rubber is acidic. The high temperature resistance of the more acidic mixed rubber decreases when the vulcanization is delayed. Adding appropriate weak alkaline material can improve the acidity content of slurry. The PH value of slurry in the range of neutral or weak alkaline is conducive to the improvement of elasticity and curing speed.

The addition of silica gel or structural control agent is too much, the elastic recovery of mixed rubber is poor, and the vulcanization rate is slow; Adding too much internal plasticizer or structural control agent will make the compound has a curing delay effect, resulting in the deterioration of the resilience of the compound and slow curing speed. The raw rubber with narrow molecular weight distribution and certain volatile components was selected to improve the demoulding of the mixed rubber and reduce the dosage of plasticizer. With alkoxy silane treated the surface of silica, with hydroxyl silicone oil, the use of two-step method to make silica molecules and raw rubber molecules have a certain combination of reaction time, technically can keep in good health, reduce the use of structural control agent, increase the rubber resilience and elasticity

Reason: Because of the high water permeability of silica gel, especially the silica gel made by precipitation method, with the increase of relative humidity in the air, the water content of the silica gel also increases linearly. When the water is too much, the silica gel mixture becomes opaque from transparent, especially in the winter, the ambient temperature is low, so the water loss time of the mixed rubber surface will be slow, or not fall off at all, and the surface of the extruded product is easy to become bubbles. General precipitation silica is not suitable as silicone rubber filler for extrusion molding because of its high water content.

Solution: using alkoxy silane to treat the surface of silica, make the hydrophilic surface into hydrophobic surface, can reduce the water absorption rate; Can also reduce the water absorption of slurry through high temperature treatment, improve the bubble of extruded slurry. At present, the extruded rubber is in production. In the existing formula system, the extruded rubber is further vacuumized and heat treated to strictly control the effective mixing time and temperature, that is, the mixing time and temperature of the high temperature section, so as to improve the bubble problem of the extruded rubber. At the same time, drawing standard vulcanization curve for various types of rubber materials is also a means to stabilize the production quality of the mixed rubber.

The above introduction is the cause and solution of several common problems of silica gel mixing rubber, if you need to know more, you can contact us at any time!