Cyanoacrylate Adhesive Environmental Resistance

Laurie Gibbons
Adhesive Properties, Environmental Resistance
July 2, 2015

cyano

Chemical Resistance of Cyanoacrylate Adhesive

It doesn’t seem logical, but cyanoacrylate adhesives have more chemical resistance to gasoline than they do to water.  One customer who used acetone to remove excess adhesive wanted to speed up the process.  So he tried toluene which is normally thought of as a stronger solvent.  The toluene didn’t seem to have much effect at all. The bottom line is cyanoacrylates have poor resistance to polar solvents and better resistance to non-polar solvents.

The dielectric constant of each solvent provides a general measure of a solvent’s polarity.  Water is very polar and (at 70°F the dielectric constant is 80.  Gasoline is non-polar at 70°F the dielectric constant is 2.  Although water will remove it over time, manufacturers recommend removing cyanoacrylate adhesive with acetone which has a dielectric constant of 21 and nitromethane which is 36.  Both acetone and nitromethane are polar aprotic solvents.

Other factors that affect the chemical resistance of the bond include temperature and bond design.

Heat resistance of Cyanoacrylate Adhesive

The following chart shows the % strength retention of cyanoacrylates.  Standard cyanoacrylates retain about 50% of their original strength at 80°C.  Enhanced grades retain 50% strength to 120°C.  Special high temperature grades resist much higher temperatures.  To activate the high temperature resistance, the following secondary curing mechanism enables additional cross linking of the polymer, allowing the cured adhesive to resist higher temperatures.  Note: this procedure will only activate the high temperature resistance designed into specialty grades.  It will not improve the temperature resistance of other grades.

1) Parts are bonded and clamped at room temperature for four hours.

2) The clamped parts are then heated at 150°C (302°F) for two hours.

3) Then, after the two hours, the bond will be thermally resistant up to 250°C (482°).

For resistance to 200°C (392°F) with no need for a secondary heat cure choose Permabond 825 (Patented Technology)

cyano resistance

For further help and advice, please contact Permabond.

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