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Hybrid Dual-Curing Adhesives Address Light-Curing Limitations

Posted on 9/25/2018 7:03:10 AM By ASC
  

Light-curing adhesives are often preferred in manufacturing industries owing to the productivity benefits they confer as well as the accuracy with which they can be applied.  There are, however, limiting factors. They cannot be used at temperatures higher than 150°C and they are not resistant to chemical exposure or oil. In addition, shadows cast by the components can limit light exposure, and without this, the adhesive fails to cure.

Dual curing adhesives provide a solution. For example, when there are shadowed areas, a dual curing adhesive will work with a second curing mechanism such as humidity, heat, or exposure to anaerobic conditions.

When natural air humidity acts as the second curing mechanism, manufacturers need not use any additional equipment. The process is therefore the same as it would be with a light-curing adhesive. However, these adhesives are not resistant to high temperatures and will only tolerate moderate chemical exposure. UV silicones work in much the same way and can tolerate high temperatures, but they have low bond strength andare only used as sealants.

Adhesives that couple light-curing with anaerobic curing offer a middle-road solution. They will tolerate temperatures of up to 180°C and will resist harsh chemicals like brake fluid and oil.

Dual-curing adhesives that use light and heat offer the widest diversity of adhesive types ranging from flexible, dynamic-stress-tolerant acrylates to hard, chemical and heat resistant epoxies. Manufacturers first expose the adhesive to light, fixing the components in place so that they will not shift during heat-curing. Then heat is applied using convection or tunnel ovens, induction, or thermodes, curing the adhesive at temperatures from 100 to 120°C.



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