Silane oligomers are functional silanes grafted together via Si-O-Si linkage. They allow formulators of coatings, adhesives and sealants to improve performance of the coated substrate(s). They have several unique benefits over traditional silanes.
Silane oligomers are short chain polymers of silane monomers, bonded together at the siloxy linkage. The number of monomers in this comb-like structure is typically 10 to 100.
These oligomers bond to the substrate with greater efficiency once hydrolyzed. Due to their orientation, less silane is caught up within the coating or adhesive and more at the interface as a functional layer. These functional layers strengthen bonds between inorganics and organics resulting in improved rub and mar resistance, improved water resistance and decreased VOC concern.
Example: The structure of CoatOSil MP-200, an oligomer of the Silquest A-187 monomer [bracketed as the repeating unit]
Flexibility of use - water and solvent based products
Oligomeric silanes, due to their structure, can be formulated into either water or solvent based products providing long term shelf stability and improved adhesion to organic substrates, filler and pigments. Most silanes can be used in solvent based products or in waterbased primers (when the primer is formulated and used in a short period of time - pH dependent, up to a few days). This flexibility can allow formulators to achieve improved adhesion and shelf stability in water based coatings without limiting shelf stability.
In creating the Si-O-Si bonds between each silane group, over 60% of the methanol or ethanol is driven out of the silane, yielding large reductions of HAPs or VOC (depending on whether the initial monomer is a methoxy or ethoxysilane).
Improved Durability/Rub Resistance
Pre-reacting the silanes into oligomers changes them into hydrophobic additives. When used as a replacement for a latex cross linker or as a high solids paint crosslinker, oligomeric silanes can improve wet scrub resistance dramatically.
Due to the Si-O-Si bonds in the silane oligomers are more hydrophobic than standard silanes. This benefit translates directly to the formulated product. Imagine the potential applications of a water based, hydrophilic coating with great adhesion to metal, concrete or masonry.
Improved adhesion vs traditional silanes
Oligomeric silanes migrate toward towards inorganic substances and result in a stronger bond than standard silanes, which can become bound in the coating or adhesive itself. This layer is also more uniformly oriented, forming a stronger tie later to organic resins.