The amount of silane coupling agent is large and there are many varieties of it, generally, its structure is represented by Y-R-SiX3. The X of it is halogen or alkoxy group. Under the action of water, Si-X becomes Si-OH to realize the connection between the inorganic surface and silane.

R is long-chain alkane, and Y is organic functional group such as amino group, vinyl group, methacryloyloxy group, mercapto group, epoxy group, etc., which is easy to react with the polymer. Silane coupling agents are widely used in the surface modification of nanoparticles, anti-corrosion surface treatment of glass fibers and metals, and tackifiers for coatings and sealants, which can greatly improve material performance.

Ⅰ. The application of silane coupling agents

One of the main application areas of silane coupling agents is the treatment of inorganic fillers used in organic polymers. The latter can be treated with silane coupling agent to convert its hydrophilic surface into an organophilic surface, which can not only avoid sharp thickening of particle agglometration and polymer in the system, but also improve the wetting of organic polymers to reinforcing fillers. Besides, the carbon-functional silane can make the reinforcing filler and the polymer achieve strong bonding.

However, the effect of the silane coupling agent is also related to the type and amount of the silane coupling agent, the characteristics of the substrate, the properties of the resin or polymer, as well as the application occasion, method and conditions.

There are two methods of using silane coupling agent, namely surface treatment method and integral blending method. The former method is to treat the surface of the substrate with a dilute solution of the silane coupling agent; the latter method is to directly add the silane coupling agent stock solution or solution to the mixture made of polymer and filler, so it is especially suitable for materials systems that require stirring and mixing.

Ⅱ. Influence of nano-calcium carbonate modified by amido silane coupling agents on the properties of silicone sealant

1. The viscosity of the base material has a tendency to increase for the samples that have been dry-modified by the amino silane coupling agent; and with the increase of the number of amino functional groups, the viscosity and thixotropic index of the base material also show an increasing trend. The extrusion rate of the base material decreases accordingly (time increases).

2. After modification by different amine silane coupling agents, the mechanical properties and adhesive property of the corresponding silicone sealants have been improved, especially the elongation has been improved significantly. In the case of the same particle size, the improvement of mechanical properties is mainly due to the good dispersion of nano-calcium carbonate particles in the 107 colloid system and the improvement of the inorganic-organic interface adhesion.

The Bonding effect of the silicone sealant prepared by N-(γ-dimethylaminopropyl)-γ-aminopropylmethyldimethoxysilane and the new hindered triaminosilane-modified nano-calcium carbonate is obviously superior to the silicone sealant made of γ-aminopropyltriethoxysilane modified nano-calcium carbonate, indicating that the number of amine groups plays a key role in the modification effect to a certain extent.

3. With the increase of the number of active amine groups in the modifier, the water resistance performance of the silicone adhesive will be better.