Compatibility of EPDM Rubber Gaskets with Structural Silicones

Compatibility of EPDM Rubber Gaskets with Structural Silicones

In most Glazing & Curtain-wall applications, EPDM Rubber Gaskets and Setting Blocks come in contact with Silicone Sealants (originating from DOW CORNING, TREMCO, SIKA, MOMENTIVE etc.) and therefore Silicone Compatibility of these EPDM Gaskets is an area of concern. Compatibility is basically the ability of different materials to blend and form a homogeneous system or the ability of different materials to exist in contact or close proximity to each other while having no ‘malicious or deprecating’ effects on each other.

There are many conditions when compatibility should be addressed including Full Structural Contact, Non-structural applications and Incidental Contact (Point Contact). In Structural applications - Structural Silicone Adhesives bond the glass to the Metal Framing System. Rubber Gaskets are used to provide the proper size and position of the structural seal. Since there is a "direct contact" between the Gaskets and the Structural Silicone, it is necessary the Full Compatibility is established. In incidental contact (point contact) and nonstructural applications such as cap bead or weather seal, only a degree of compatibility is required.


Adhesion is another aspect of Silicon Compatibility, but adhesion does not imply compatibility and conversely, compatibility does not imply adhesion. Adhesion is basically a pass/fail rating that describes how well silicone sealant adheres to a material such as a Gasket.

As adhesion results vary, KASTRADE suggests you consult sealant supplier to confirm adhesion to gaskets or any other substrate.

In normal cases, all KASTRADE EPDM Rubber Gaskets have been tested and approved by major manufacturers of silicone sealant for Incidental Contact (Point Contact) and Non-Structural applications. These Gaskets include both Solid (Dense) EPDM as well as cellular (Sponge) EPDMs.

KASTRADE with the help of DSM Elastomers, Holland have developed a special EPDM Rubber Compound (Ref. SCR520) which is fluid free and there is no migration of any type from the Rubber to the structural Silicone. This compound has been tested and approved for FULL CONTACT by the leading Structural Silicone Manufacturers/Suppliers like DOW CORNING under most stringent test conditions. (A certificate can be produced upon request).

Gaskets produced out of this EPDM Compound have been successfully delivered to various Projects in the Middle East.

KASTRADE is of the opinion that Critical Façade applications or Structurally Glazed Systems should be retested as part of routine compatibility review. The user/customers responsible for verification of compatibility and suitability of any products used in the glazing process.

In case you need any further information on this subject you are requested to send a mail to

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