Cyanoacrylates volatility

Surface primers Very high, to the limit of the plastic Simple process Only for cyanoacrylates, volatile solvents in primer, extra process step Low Medium Low for cyanoacrylates, good for reactive acrylates... 

Since bases are catalysts for the curing reaction and acids are stabilizers for the cyanoacrylates, the pH value of the surface will control the cure speed. Surfaces that tend to be acidic will cure slowly compared to a neutral surface, which in turn will cure more slowly than an alkaline surface. In most applications the objective is to speed the cure therefore, all the commercially available activators are weak bases dissolved in a volatile carrier. Applying an activator to a surface places a layer of the weak base in position to initiate the cure. Since they are stronger bases than moisture, they are able to neutralize the stabilizer systems in the adhesive more effectively, and thus they can tolerate larger gaps than would be possible with moisture alone. In general, the fixturing time is 10 times faster with activator than without it. Even with activator, the effect of the gap is clear (see Table 4). 

A low-toxicity, low volatility solvent for general cleaning applications. Especially suited for use in cleaning of uncured polymers, such as epoxies, urethanes, and silicones. Also very effective for dissolving cured cyanoacrylate instant glues. 

One method to reduce the volatility of sulfur dioxide is to complex it with imidazole and then add the complex to the adhesive. Chelates of boric acid derivatives with polyhydroxy compounds have also been prepared as anionic polymerization inhibitors. The chelates can be preformed or prepared in situ by adding the boric acid compound and the polyhydroxy compound to the adhesive. Sulfamides have been used to stabilize cyanoacrylates. The sulfamides (24) in question are prepared by reacting sulfuryl diisocyanate (23) with active hydrogen compounds such as carboxylic acids, as shown in Eq. (7). ... 

Obviously a great deal of research effort has been directed toward developing stabilizers for cyanoacrylate adhesives. Two major types have evolved the volatile acid gases and the nonvolatile acids. These are used in varying concentrations, depending upon the type of stabilizer. Table III is a summary of the types of stabilizers used and typical concentrations. The end use of the adhesive also dictates the type and level of inhibitor used a fast-curing industrial ethyl cyanoacrylate adhesive will tolerate much... 

The first examples of thickened cyanoacrylate adhesives were described by Coover and Shearer in a U.S. Patent. The thickeners cited and claimed were polyalkyl cyanoacrylates, polyacrylates, polymethacrylates, cellulose nitrate, and cellulose organic acid esters, such as cellulose acetate butyrate. Several years later. Wicker and Shearer improved the process for thickening cyanoacrylates. Instead of adding the thickener directly to the monomer, the thickener was first dissolved in a volatile solvent and then added to the ester. The solvent was then vacuum stripped to give the thickened adhesive. The authors claimed that this process gave adhesives having better clarity, better storage stability, and faster cure speed than adhesives prepared by the older method. 

Application of cyanoacrylates to the bonding surface is simple, for these are one-part, 100% reactive adhesives. The adhesive is applied as a drop or bead to one surface, then the other adherend is used to spread the adhesive in a thin film. Due to the volatility of the monomer and the fast cure, no more than three or four square inches of bondline should be open at one time. Enough adhesive should be applied to provide a slight fillet when the adherends are mated. This will ensure that the adherends are thoroughly wetted and that any air bubbles are removed. On impervious, well-fitted substrates, two drops (25 mg) of adhesive per square inch is sufficient coverage. Too much adhesive will create a weak bond, as the surface-initiated cure may not extend throughout a thick adhesive layer. Also, excessive adhesive can wash the initiators out of the bondline, causing a slow or incomplete cure. 

Volatile cyanoacrylate monomers, in particular methyl and ethyl cyanoacrylates, have characteristic acrid odors. Exposure to these materials at levels in the range of 1-5 ppm results in irritation to the eyes, nose, and throat (3). It is recommended that these monomers be used in a well-ventilated area, that skin and eye contact be avoided, and that the user be familiar with the relevant safety data supplied by product manufacturers. A recent epidemiological study in workers with occupational exposure to monomer vapors concluded that there was no increased risk of pulmonary obstruction (eg, asthma) on exposure to average short-time concentrations of less than 0.5 ppm (60). Polymerization of cyanoacrylates is rapid and exothermic and particular care should be taken to avoid bums, which can result from the unexpected bulk polymerization of inadequately stabilized or contaminated monomer samples. 

Typical procedure. 2-Cyanoacryloyl chloride [1008] 2-Cyanoacrylic acid (2.0 g) was dissolved in hot p-xylene (250 mL) containing y-propanesultone (1 mg). Some 50 mL of the xylene was then removed by distillation, and the concentrated solution was filtered and cooled to 40 °C. Me2NCHO (5 mg stock solution in benzene) was added, and then oxalyl chloride (6 mL) was added dropwise with stirring under a continuous flow of Ar. The mixture was stirred for 12 h at room temperature, then ethyl furfurylidenecyanoacetate (5 mg) was added and the volatiles (along with a part of the solvent) were removed in vacuo to give 100 mL of a clear yellow solution of 2-cyanoacryloyl chloride in xylene. 

Several methods have been specifically developed for the preparation of replicas for the SEM. Peck [291] developed a method to determine the nature and location of volatile and nonvolatile smoke deposits on cigarette filters. Eastman 910 adhesive, methyl-2-cyanoacrylate monomer liquid, was heated and vaporized adjacent to the specimen as the in situ replicating material. Eastman 910 apparently works well because it polymerizes rapidly in a water environment. However, as a result of the reaction in water, best results are obtained when producing the replica in a dry nitrogen atmosphere. 

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