Effects of fumed silica and nano-calcium carbonate on the properties of silicone rubber

Silicone sealants are widely used in construction, electrical and electronic, aerospace, automobile industry, medicine and health and other fields because of their excellent bonding and sealing properties, non-corrosiveness to substrates, excellent weather resistance and easy use.

After the addition of reinforcing fillers (fumed silica and nano-calcium carbonate), the mechanical properties of silicone rubber are often greatly improved, but excessive use of fumed silica will cause serious structure of the rubber compound and poor operability. The different moisture content of nano calcium carbonate will affect the appearance of silica gel. Yang Yuqi et al. studied the effect of different dosages of fumed silica and the moisture of different nano calcium carbonate on the performance of one-component dealcoholated RTV-1 silicone rubber. The results show that:

(1) The performance of the silicone rubber prepared by the fumed silica after baking is better than that of the unbaked fumed silica. The possible reason is that fumed silica has a strong attraction due to the presence of silanol on the surface, and it can absorb water by forming chemical bonds with water molecules in the air to a certain force.

(2) Different dosages of fumed silica have an impact on the performance of the silicone rubber. When the dosage is 20%, its performance reaches the best; this is because fumed silica is added and is easy to disperse in the base material. , it is physically cross-linked with silicone rubber, which increases the cross-linking density of the material, thereby increasing the tensile strength and elongation at break, but as the content of fumed silica reaches a certain level, fumed silica does not If it is easy to disperse, agglomeration may occur, resulting in a decrease in the tensile strength and elongation at break of the silicone rubber.

(3) When the water content of nano calcium carbonate is less than or equal to 0.5%, the appearance, viscosity and extrudability of the prepared silicone adhesive are better. This is because when the water content is high, the hydroxyl groups on the surface will increase, and the rubber will have a tendency to coagulate each other, forming a three-dimensional network under the action of the base rubber, so that the viscosity of the rubber will increase, and the water content will be too high and cross-linking. The reaction of the agent, etc., will generate particulate matter, resulting in poor product dispersibility and particle appearance.