Coatings & Construction / Solution Family

Specialty Silanes

Thiol- and sulfide-functional silanes u2014 led by mercaptopropyltrimethoxysilane u2014 for adhesion promotion and sulfur-reactive coupling in coatings, sealants, and rubber-modified systems.

Overview

Functional silanes carry a reactive organic group, such as a thiol or a sulfide,nthat bonds to organic polymers while the alkoxy end bonds to inorganic surfaces.nMercaptopropyltrimethoxysilane (CAS 4420-74-0) is the mercapto (thiol) silane in this family;nits -SH group couples to sulfur-cured systems and promotes adhesion to metal and mineralnsurfaces in coatings and sealants. Specify a mercapto silane where you need a sulfur-reactivencoupling site instead of the amine or epoxy functionality of the other silane families.

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The thiol group is both the strength and the limitation. It reacts readily with sulfur andnunsaturated resins, giving strong covalent coupling, but mercapto silanes carry ancharacteristic odor and can interact with some cure catalysts, so handling and order ofnaddition matter. Dose to the filler surface area you actually need to treat instead ofnoverloading the system; excess silane adds cost and can plasticize the matrix withoutnimproving adhesion.

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A closely related material, bis-[3-(triethoxysilyl)propyl] disulfide (often sold as Si-75),nis a sulfide-functional silane used mainly as a coupling agent in silica-reinforced tire andnrubber compounds. The catalog tags it for Plastics & Polymers and Industrial Manufacturingnrather than coatings, so it is surfaced on those industry pages instead of this one. Forncoatings and sealant adhesion, the mercapto silane above is the grounded choice.

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Where it's used
  • Adhesion promotion between organic coatings/sealants and metal or mineral substrates
  • Sulfur-reactive coupling in unsaturated-resin and rubber-modified systems
  • Surface treatment of mineral fillers to improve dispersion and bonding
  • Primer and tie-coat formulations requiring a thiol-functional coupling site
Frequently asked questions
What is a mercapto silane used for?
A mercapto silane such as mercaptopropyltrimethoxysilane has a thiol (-SH) group that couples to sulfur-cured systems and unsaturated resins while its trimethoxysilyl end bonds to metal and mineral surfaces. In coatings and sealants it acts as an adhesion promoter and coupling agent between the organic and inorganic phases.
How is a mercapto silane different from an amino or epoxy silane?
The difference is the reactive organic group. Mercapto silanes carry a thiol that reacts with sulfur and unsaturation; amino silanes carry an amine that reacts with epoxy and other electrophiles; epoxy silanes carry a glycidyl group. Choose the functionality that matches your resin chemistry and cure system.
Does RawSource supply sulfide silanes like Si-75 for coatings?
Bis-[3-(triethoxysilyl)propyl] disulfide (Si-75) is in the catalog, but it is classified for plastics, rubber, and industrial manufacturing (chiefly silica-reinforced tire compounds) rather than coatings. For coatings and sealant adhesion, mercaptopropyltrimethoxysilane is the recommended specialty silane.
Disclaimer. Information on this page is provided for general reference and compiled from authoritative public sources (e.g. PubChem/ECHA). Values are typical and are not a guaranteed specification; the Certificate of Analysis (CoA) for the lot you purchase governs. Products are sold for industrial and professional use only. Nothing here is a medical, health, or efficacy claim. Always consult the current Safety Data Sheet (SDS) before handling, and confirm regulatory status, classification, and suitability for your application and jurisdiction.
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