Silane Coupling Agents: Techno Brief

Coupling agents are adhesion promoters that are used to provide a stable bond by reducing the interfacial tension between the fibrous or particulate inorganic component and the organic matrix polymer in reinforced and filled plastics. This Coupling Agents guide is designed to help you understand more about the use of silanes as coupling agents in reinforced plastics, focusing on the benefits and main applications.

Silane Chemistry

A silane is a molecule containing a central silicon atom bonded to two types of groups: Alkoxy groups and organo-functional groups.

These two type of groups exhibit different reactivity and allow sequential reactions. In the crosslinking process, the first step is generally the grafting of the silane the polymer backbone the linking of the polymer chains via condensation of silanols.

Click on the different atoms of the molecule below to view their properties.

Silane Coupling Agents Mechanism

Silane coupling agents are silicon-based chemicals that contain two types of reactivity--inorganic and organic--in the same molecule. A typical general structure is Y-Si(OR)3 where OR is a hydrolyzable group such as methoxy, ethoxy, or acetoxy, and XY is an organofunctional group such as amino, methacryloxy, epoxy, etc. A simplified picture of the coupling mechanism is shown in the figure below.

A silane coupling agent will act as a link between an inorganic substrate (such as glass, metal, mineral) and an organic material (such as an organic polymer, coating, adhesive) to bond, or couple, the two dissimilar materials together.

Figure 1 : Silane coupling mechanism

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