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.

Clays in rubber

The most extensively used filler reinforcement for rubbers is carbon black, which is self-coupling and gives excellent results. The demand for rubber articles in colors other than black, yet with good mechanical properties, has inspired the search for suitable white and colored fillers with similar beneficial effects. 

Silane coupling agents are the key to satisfying this need by providing a method of effectively bonding various inorganics to the rubber phase.

Most of the common peroxide or sulfur-cured elastomers are reported to show improved strengths (tensile and tear) with silane treated clay reinforcements. Treatment of clay silanes also helps to optimize the electrical insulating properties of clay-filled rubber. 

Similar improvements in the performance of clay as a reinforcement can be obtained by treating the clay in situ while compounding with the rubber. In such cases, the clay, rubber and silane should be compounded separately before adding ingredients. This is done to allow the silane the opportunity to migrate to and react with the mineral surface before the other ingredients have the opportunity to interfere with this reaction.

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