Cyanoacrylate adhesives
Cyanoacrylate adhesives are commonly known as “instant adhesives”. These are low-viscosity or deliberately thickened esters of cyanoacrylic acid, which are commercially available in 1K form as monomers and react by polymerization reaction in the joint gap to form the actual adhesive polymer. Polar groups, such as the OH ions in the moisture layer at the surface of the part to be joined, must be present for curing to begin. This involves anionic polymerization, i.e. nucleophiles, such as organic nitrogen compounds, sulfur compounds, or alcohols and water, attacking the double bond in the monomer molecule. The polymerization process here is very fast, so that a solid compound is formed within a few seconds.
Cyanoacrylate adhesives – the applications
Preferred substrates include metals, glass or ceramics, which allow for an extremely thin bonding gap. To fill slightly wider gaps, additives are used to raise the viscosity or thixothropic agents are used to create a gel state. Such types are preferably used for bonding EPDM rubber seals.