Difference Between α-Silane and γ-Silane

Silane coupling agent is a type of organic silicon compound that contains two different chemical groups in the molecule. It can build a "molecular bridge" between the interface of inorganic substances and organic substances, connecting two materials with widely different properties. It can simultaneously improve the performance of composite materials and increase bonding strength. It is widely used in thermosetting resin composite materials, thermoplastic resin composite materials, inorganic fillers, coatings, adhesives, sealants and other fields.

There are many kinds of γ-silanes, which are widely used in the market, and its organic functional active group X can vary according to the nature of the organic polymer. For example, silane may contain amino, epoxy, glycidoxy, mercapto, thio, isocyanate, methacryloxy and vinyl groups. The connection to the inorganic substrate is on the other side via a hydrolyzable functional group OR. The functional group OR mainly uses methoxy and ethoxy. These alkoxy groups of the silane are hydrolyzing upon exposure to moisture in the air. Reactive silanols are formed upon hydrolysis. The reactive silanols then undergo condensation reactions to form siloxane polymer networks or react with inorganic substrates.

In 1984, the Department of Chemistry of Nanjing University published an article analyzing in detail the properties and synthesis methods of α-functional silane coupling agents based on the structural characteristics of silane. It was believed that α-functional silane coupling agents can significantly improve the adhesion to materials and improve resistance to moisture and heat properties improve the surface drying time of the sealant. Since the electron-pushing group in alpha silane is blocked by only one methylene group, its cross-linking reaction speed is greatly increased. It can be cured normally without a tin catalyst in a general formula system. When used in silicone rubber, it can be significantly reduced. The amount of organotin catalyst used. For highly active Diethylaminomethyltriethoxysilane(ND-22) can not use catalyst. According to its research results, the α-silane coupling agents currently used on the market mainly include ND-22, (N-Phenylamino)methyltriethoxysilane (ND-42), etc. However, these silane coupling agents are easy to change color and have poor stability. , is greatly restricted in silane application.

Although the stability of alpha functional group silane is not as good as gamma functional group silane, its synthesis method is simple, the source of raw materials is easy, and it has good heat resistance.