Silane coupling agent is one of the important and widely used treatment agents. It was originally developed as a treatment for FPR glass fibers. Since then, with the development of new compounds, they have been gradually applied in various fields. Now, silane coupling agents are basically suitable for the joining surfaces of all inorganic and organic materials.

1. Direct mixing method of silane coupling agent

Direct mixing method: The direct addition of silane to the batch is the easiest method for coupling modification of particulate fillers in liquid resins. For example, when mixing rubber, it is directly mixed with silane particulate filler for immediate treatment. The effect of silane incorporation depends on the silane adsorption capacity of the filler during the mixing operation.

Treatment of filler with organic solvent of silane: This method is to mix the filler with a dilute solution of silane in organic solvent, then filter and dry. Compared with the case of using an aqueous solution, the anhydrous solvent makes the silane coupling agent deposited on the surface of the filler closer to a monolayer, and the treated fine particle filler is different from the case of the aqueous solution, and does not agglomerate when dried.

Treatment of fillers with aqueous solutions: Silane (and other complexing agents) dispersions in water are almost always used in the treatment of glass fibers. Coarse fillers such as glass beads and glass fibers are very effective to treat with aqueous solutions, dry easily and do not clump. Fine particle fillers can also be treated with an aqueous solution, but spray drying is required to avoid clumping.

2. Dry mixing method of silane coupling agent

Fillers are treated with dry blending in the hope that the high surface area filler will retain a large amount of silane in a stable dry powder form so that when it is dry blended with resin or other untreated fillers, there will be monomeric silane available for migration. Sufficient dispersion of the silane on the filler surface can take more than a few days.

Usual shipping and storage times are sufficient to adequately disperse the silane on the bulk filler. In general, ethoxysilanes or propoxysilanes are much more stable on the filler surface than methoxysilanes. When using silane coupling agent in composite materials, it is necessary to fully consider the characteristics of organic polymers and inorganic materials, select the appropriate silane coupling agent, and choose the correct method of use according to its production process characteristics, so as to obtain economical and satisfactory results.