Cyanoacrylate environmental resistance

For adhesive bonding of PES to itself or to other materials, epoxy adhesives are generally used. Cyanoacrylates provide good bond strength if environmental resistance is not a factor. Parts made from PES can be cleaned using ethanol, methanol, isopropanol, or low-boiling petroleum ether. Solvents that should not be used are acetone, MEK, perchloroeth-ylene, tetrahydrofuran, toluene, and methylene chloride. 

In contrast to the attention given to the bonding of aluminum and wood, very few studies have been reported dealing with the durability of other structurally bonded systems." A limited amount of sustained load durability data is available for steel bonded with epoxies and aluminum bonded with urethanesin recent years, reports have appeared dealing with the environmental resistance of modified acrylics and cyanoacrylates. Brockmann has also reported on the durability of steel joints exposed to hostile environments. " ... 

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. 

Epoxies cure to become thermoset adhesives and so show excellent humidity resistance, especially if one of the substrates is metal. For long-term, durable adhesively bonded metal-to-metal joints, toughened epoxies are hard to beat [6] but where plastics are involved, some of the other technology adhesives invariably offer benefits in terms of ease of application and cure speed whilst still retaining satisfactory environmental resistance. Indeed epoxies do not often show good adhesion to elastomers and for the thermoplastic elastomers cyanoacrylates will generally show the best environmental resistance. 

UV-curing aerobic acrylic adhesives, while less expensive on a per pound basis than cyanoacrylates, provide a structural wire-tack that resists environmental conditions. A useful property is that the aerobic acrylics fluoresce to optimum brightness only upon completion of cure, providing a visual means of end-point determination. An elastomer formulation is recommended for permanent wire-tacking in a high vibration environment. Removable wire-tacking formulations are also available (Fig. 1). 

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