The role and effect of silane coupling agents have been recognized and affirmed by people, but why does a very small amount of coupling agents on the interface have such a significant impact on the performance of composite materials? There is still no complete set of coupling mechanisms to explain it?

1. Chemical binding theory: the most common and most common mechanism of action, but it should be noted that the formation of chemical bonds must meet a certain amount of quantization conditions, in addition to chemical bonds, there are also intermolecular forces;

2. Wetting effect and surface energy theory: improve the wettability of organic/inorganic substances with large differences in properties, and enhance the mutual, wetting and adsorption of two materials with different properties;

3. The theory of deformable layer formed at the interface: resin solidification and cooling will produce heat shrinkage, and the expansion coefficient of inorganic materials is much smaller than that of organic resins, resulting in interfacial stress. The silane coupling agent exists in the interfacial area, which produces an interpenetrating polymer network during crosslinking, forms a flexible resin layer, and eliminates residual stress;

4. Constrained layer theory: The resin in the inorganic filler region should have a modulus between the inorganic filler and the matrix resin, and the function of the coupling agent is to "tighten" the polymer structure in the interphase region. The surface of glass, silica and some inorganic materials has the side effect of inhibiting the curing of polyester and epoxy resins. If silane is used for modification, the coupling agent will restrict the effect of inorganic fillers on curing.