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.

Silica Treatment in Epoxy Resin

Epoxy mineral composites find extensive use in electrical molding and casting compositions. Silane coupling agents preserve insulating and low loss properties of epoxies by exclusion of water during prolonged environmental exposure. Silane coupling agents also improve physical properties.

Silica-filled epoxy systems are greatly benefited by inclusion of a coupling agent such as Z-6040 epoxy functional silane. Addition of Z-6040 in silica-filled epoxy system lead to a significant improvement of electrical and mechanical properties, as shown in the table below. The improvement in wet environment is particularly dramatic.

1% silane treatment Flexural Strength
Volume resistivity
Dissipation Factor
x 102
Dry Wet* Dry Wet* Dry Wet*
None 18 800 14 900 2.2 x 1015 1.9 x 1012 0.0051 0.053
Z-6040 Silane 22 400 18 500 1.1 x 1015 6.4 x 1014 0.0046 0.014

* After 4 hours immersion in boiling water

Table 1 : Performance of silane coupling agent in silica reinforced epoxy resin

Birla Carbon Black
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