Metals Associated with Cyanoacrylate Adhesives

The industrial manufacturing process for cyanoacrylate monomers is designed to generate pure organic compounds free of metals. The prepared monomer is functionally very reactive and is polymerised by several mechanisms of which the most common is by anionic methods. In most applications the initiation is usually carried out by the nucleophilic contaminant (water or moisture) found on most surfaces. These adhesives differ from other adhesives in that they are monofunctional and can homopolymerise rapidly at room temperature. A number of modifiers have been added to impart a range of desired properties and these include stabilisers, inhibitors, thickeners, plasticisers, tracers, colorants and preservatives. 

Most cyanoacrylate adhesives are maintained in a liquid state at room temperature by the addition of free radical and anionic stabilisers at suitable concentrations so as not to interfere with the functionality of the adhesive. These stabilisers/inhibitors are added at 

Sultones were the earliest anionic stabilisers used in cyanoacrylates but fell from favour because of their potential carcinogenicity. Chelates of boric acid derivatives with polyhydroxy compounds also were considered as anionic inhibitors. Anionic inhibitors are normally added at concentrations between 0.001 and 0.01% depending on the application. 

Typical free radical inhibitors added as hydroquinone monomer acrylether (HQ), or other hindered phenolics, etc., are employed at concentrations from 0.2 to 0.5% depending on the type of cyanoacrylate ester and its additives. 

6 Non-Destructive Methods of Analysis for Metals Content in Cyanoacrylate Adhesives 

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