グローバルシリコーンソリューションパートナー
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Organofunctional silanes for coupling, adhesion, crosslinking and surface treatment: amino, epoxy, vinyl, methacryloxy, sulfur, isocyanate, alkyl, fluoroalkyl and phenyl silanes, orthosilicates, RTV crosslinkers and polypropylene donors.
An organofunctional silane carries two kinds of reactive group on one silicon atom. Its hydrolysable groups — methoxy, ethoxy, acetoxy or oxime — react with water to form silanols that bond to glass, minerals and metals. Its organic group is chosen to react with, or entangle in, a polymer. That dual reactivity is why a small molecule can work as a coupling agent, an adhesion promoter, a crosslinker or a surface modifier, depending on the group it carries.
The range below is grouped by that organic group, which is how most formulators choose a silane: first by the polymer it has to work with, then by how fast and how densely it should react.
Primary and secondary amines react with epoxies, urethanes, phenolics and acrylics, which makes amino silanes the most widely used adhesion promoters and filler coupling agents. Diamino and triamino grades add reactive sites. Alpha-silanes, where the amine sits one carbon from silicon, hydrolyse far faster than their gamma (propyl) counterparts and suit fast-curing silane-terminated polymers.
Glycidoxy and epoxycyclohexyl groups react with amines, anhydrides, carboxyl and hydroxyl groups. Epoxy silanes couple glass and minerals to epoxy and acrylic resins, promote adhesion in sealants, and crosslink water-based coatings. Methyl-dialkoxy grades form a looser, more flexible interface; the oligomer releases less alcohol.
Vinyl groups take part in free-radical grafting and copolymerisation. Grafted onto polyethylene and then cured with moisture, vinyltrimethoxysilane is the basis of silane-crosslinked polyethylene for cable insulation and pipes (see silane-crosslinked XLPE). Vinyl silanes also scavenge moisture in sealants and serve as crosslinkers in one-part RTV silicones.
The methacrylate group copolymerises with acrylics, styrene and unsaturated polyester, so these silanes couple glass fibre and silica fillers into those resins and bring hydrolysable silicon into acrylic coatings and adhesives.
Polysulfide silanes bond silica to rubber during vulcanisation; in silica-filled tyre treads that coupling is what lowers rolling resistance while keeping wear resistance. Mercapto silanes are more reactive towards rubber and also improve the adhesion of polysulfide and polyurethane sealants. Carbon-black-supported grades are solids that are easier to dose into rubber mixes.
Isocyanate silanes react with hydroxyl and amine groups and are used to silane-terminate polyols and to graft silicon onto polymers. Ureido silanes promote adhesion with good shelf stability, including in water-based systems. The isocyanurate trisilane is suited to adhesion at elevated temperatures.
Alkyl silanes carry no reactive organic group; they make surfaces and fillers hydrophobic. Short chains (methyl, propyl) also act as crosslinkers in silicone systems. Longer chains — octyl to octadecyl — give stronger water repellency and are used on concrete and masonry and to treat fillers for plastics and rubber.
Perfluoroalkyl chains give the lowest surface energy of any silane, so the treated surface repels both water and oil. They are used for easy-clean and anti-fingerprint glass and ceramics, protective films on electronics, and to bond fluorinated resins to substrates.
Phenyl groups raise thermal stability and refractive index. These silanes are intermediates for phenyl silicone fluids, rubbers and resins, and structure-control agents in silicone rubber compounding.
Tetraalkoxysilanes carry no organic group at all: on hydrolysis they become silica. They are silica sources for sol-gel coatings, aerogels and molecular sieves, binders for precision casting, and crosslinkers for condensation-cure silicone sealants. Ethyl silicate 40 is a partially condensed oligomer with a higher silica content.
One-part room-temperature-vulcanising silicones cure with moisture through a crosslinker. Acetoxy crosslinkers cure fast and release acetic acid; oxime crosslinkers cure neutral and release methyl ethyl ketoxime, which suits metals and sensitive substrates.
Alkoxysilanes are used as external electron donors in Ziegler–Natta polymerisation of propylene, where they control the isotacticity of the polymer. See the polypropylene donor overview for the full set.
Silanes react with moisture, and many release methanol or ethanol as they do. Keep containers tightly closed, store them in a cool, dry place, and blanket opened drums with dry nitrogen where possible. Each product's SDS gives its hazards and handling in full.
For a COA, SDS or a quotation on any of these grades, contact our sales team.
