Adhesive and Sealants Industry - D.O.TACK

Effects and chemistry

Organofunctional silanes are hybrid substances, which combine the functionality of a reactive organic group with the inorganic functionality of an alkyl silicate in only one molecule (see figure). This special characteristic leads to their function as molecular bridges between inorganic materials and organic polymers.

General benefits of silanes:

  • Increased adhesion to substrates
  • Improved moisture and / or chemical resistance
  • Increased abrasion or scrub resistance
  • Improved filler dispersion
  • Water repellency

In the field of adhesives and sealants, silanes are utilized for numerous purposes, the most important of which can be summarized as follows:

• Coupling Agents

Deolink silanes are utilized in order to improve the coupling between the substrate and the type of polymer used in the adhesive and sealant. The coupling mechanism requires a stable chemical bond between the organofunctional groups and the polymer as well as the hydrolyzable groups and the substrate. The organofunctional group of silanes must be reactive and/or compatible with the polymer, whereas the silanol groups condense on the surface of the substrate after the hydrolysis.

• Moisture Scavangers

In moisture-curing hybrid sealing compounds, vinyl-silanes are often used as desiccants. Due to the relatively fast hydrolysis of the trimethoxy groups, Deolink Vinyl TM-100 is especially suited for this application. An additional positive effect of the fast hydrolysis is that it helps prevent premature curing during storage.

• Crosslinking Agents

The practice of crosslinking polymers with the addition of silanes has been used for many years and mainly plays a role in acrylates, polyethers, silicones, and polyurethanes. The crosslinking process is triggered by moisture, yet the crosslinking speed can also be influenced by the amount and type of alkoxy groups as well as the selection of the organofunctional group, among other factors. Physical properties such as tensile strength, ultimate elongation, and abrasion resistance can be improved with the addition of silanes. Often, a variety of aminosilanes are utilized for the crosslinking, but Deolink Vinyl TM-100 can also be used.

• End Capping

Adhesives and sealants based on polyurethane have been available for several years. With these products, curing and crosslinking take place due to a reaction of the isocyanate end groups (NCO groups) when moisture is present. By modifying these end groups with the addition of silanes, the goal is to replace the isocyanate groups, which are problematic from a toxicological perspective, and to optimize the physical properties. These kinds of optimized polyurethanes are generally produced by a reaction between the NCO prepolymers and aminosilanes.

In the end, these products can be utilized for structural adhesives, parquet flooring adhesives, as well as paintable sealants.

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