Light cure adhesive is ‘instantaneous’

Paul Boughton
Cyanoacrylates  adhesives are good assembly products for general purpose, quick setting and are  simple to apply. But that general formula can be significantly improved, as with the introduction of 1770 series light curing by ThreeBond.

Light curing not only accelerates the final cure time to approximately 10 seconds (can be up to 24 hours for full cure without light activation ) but also deals with issues such as bleaching/blooming and slow curing excess. It also aids curing in wide gaps, and by using both moisture and light cure ensures a quick thorough cure where light cure alone would be affected by obscuring non-transparent material.

This makes the ThreeBond 1770 series (1771E, 1773E and 1776E) ideal for electronics and wider industrial assemblies including optics, medical, electro/mechanical assembly, eg motor shafts, ornamental products, angling accessories, toys, musical instruments, sporting equipment, jewellery and woodwork. These are all areas where non-jig placement, followed by quick and complete cure are major production benefits.

For example, advancing component miniaturisation has resulted in single components having extremely fine structures, such that conventional irradiation with sufficient light may often cause problems. In these cases, the use of an instant adhesive that combines both light and moisture curing is an effective way of providing reliable curing and bonding.

With this increasing miniaturisation, printed circuit boards also use less solder. But since bonding strength must be maintained, light-curing instant adhesives can be used to reinforce solder

Similarly, for metal plated plastic components, conventional light-curing or anaerobic resins sometimes fail to bond. In these cases, light-curing iinstantaneous adhesives are often used, due to their bonding capabilities for an even broader range of materials.

The 1770 series adhesives are traditional cyanoacrylates with the benefit of photo-anion- polymerisation to enable curing by ultraviolet or visible light. This ensures a tack free surface on curing. In the case of medical components such as hypodermic needles and syringes of course completely reliable bonding and curing is critical in their assembly - light-curing instant adhesives help to achieve these high standards. They are also used for assembly of Braille characters and graphics where other adhesives may suffer incomplete curing of excess material due to oxygen inhibition- such that touching incompletely cured portions may result in skin irritations. Light-curing instant adhesives are not affected by curing inhibition with oxygen and so eliminate the problem.

The benefits of this dual-cure system extend to its substrate suitability, where for example non-polar or highly crystalline resins, generally regarded as difficult to bond, can bond strongly. Instant adhesives generally function also as reactive ‘solvents” capable of dissolving the surfaces of certain plastic materials, including acrylic, polycarbonate and ABS. However the setting times for acrylic and polycarbonate are known to be relatively slow. This is due to the mutual solution of instant adhesive and the plastic in the bonding area. Since they cure instantly, light-curing instant adhesives can prevent the dissolution of plastic surfaces in such cases.

For more information, visit www.threebond.co.uk

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