Durability of Cyanoacrylates

Assemblies bonded with cyanoacrylate have shown entirely satisfactory long-term performance in a variety of applications particularly where at least one of the substrates is an amorphous thermoplastic or an elastomer. Typically, accelerated testing is done at high temperatures and extreme conditions to predict whether long-term bond performance will be acceptable. 

Cyanoacrylates are best suited where the bond line gap is less than 0.05 mm but, even under these conditions, the trends are clear. On steel, there was a decline in bond strength over time on aluminium, the strength dropped off more abruptly, after just 2 weeks of immersion. 

On amorphous thermoplastics, however, such as acrylonitrile butadiene styrene (ABS) and polycarbonate, standard ethyl cyanoacrylates showed excellent bond-strength 

The ability of cyanoacrylates to resist attack from moisture when bonded to polymeric substrates can be most drastically tested by subjecting bonded assemblies to autoclaving. The autoclaving process combines the environmental stresses of high temperature, high-pressure and humidity. As such, it provides a good indicator of the ability of adhesives to withstand exposure to moisture. 

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Figure 7 Durability of cyanoacrylate adhesives. Asterisk denotes substrate failure.

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