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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.

Filler Treatment

Mineral Filler treatment with Silanes

Mineral fillers have become increasingly important additives and modifiers for organic polymer. The metal hydroxyl groups on the surface of minerals are usually very hydrophobic and very incompatible with organic polymers. Silanes are a natural fit to treat the surface of the mineral to make the mineral more compatible and dispersible in the polymer, or even make the filler into a reinforcing additive.


The silane treatment can improve processing, performance, and durability of a mineral-modified product by:

  • Improving adhesion between the mineral and the polymer
  • Improving wet-out of the mineral by the polymer
  • Improving dispersion of the mineral in the polymer
  • Improving electrical properties
  • Increasing mechanical properties
  • Reducing viscosity of the filler/polymer mix

Silanes used as coupling agents in filler treatment are useful for many applications, some examples are HFFR wire & cable compounds, Mica filled polypropylene and polyamide and clays in rubber.

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