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Commonly known as superglues but more correctly termed cyanoacrylates, Loctite® instant adhesives from Henkel are formulated to cure very quickly when confined between surfaces. Surface humidity on the substrates triggers the cure reaction which moves from the substrate surfaces towards the middle of the adhesive joint.
These products are chosen for bonding small parts to achieve extremely fast fixturing and come in a variety of types optimised for specific application requirements. Selection is governed by the parts to be bonded, the loads to be resisted, the joint geometry and the process parameters. Their adhesion to most substrates is excellent and the bonding strength in shear and tensile mode is very good.
Broadly all instant adhesives, whatever their brand, are chosen for their ability to provide a quick fix. But the Loctite® range offers much more application flexibility than that. In general cyanoacrylates have limited gap filling capacity and require close fitting surfaces. There is one product in the Loctite® range however which is an important exception to this rule.
Never mind the gap
Loctite® 3090 will fill gaps up to 5mm, a unique capability in the world of superglues. It cures through the volume and won’t run out of the joint in the absence of perfect face-to-face contact or if there are any surface imperfections. This is an ideal workshop or general maintenance adhesive and can even be used to encapsulate a delicate component or part; once it has hardened it can be machined and polished. Loctite® 3090 is also a good choice where low bloom is required.
The gel consistency of the 2-part, Loctite® 3090 enables it to be easily worked into an area for maximum stress distribution. The product provides instant adhesion between most materials including porous substrates such as wood, paper, leather, cork and fabric. And it can also be used on low surface energy plastics when pre-treated with Loctite® 770 Polyolefin Primer.
A typical example of how the product is being used is as a replacement for a slow-cure silicone. The manufacturer concerned had been using this type of adhesive to secure a mechanical guard to the front of sophisticated electronic test equipment, a process that required a jig to hold the part in place for the 24hrs it took for the silicone to cure. With Loctite® 3090 the company can now achieve a bond in just two minutes, a huge saving on overall production time.
There is no comparison to Loctite® 3090 on the market and its characteristics are presenting Henkel with wide-ranging opportunities in the automotive aftermarket, in prototyping and fixturing as well as general maintenance.
High temperature instants
The exclusive capabilities of the Loctite® cyanoacrylate range don’t stop at gap filling however. While most instant adhesives can withstand a maximum temperature of 80◦C, Henkel has now upgraded a range suitable for temperatures up to 120◦C. The newcomers have all the performance attributes of their forerunners but their formulation for higher temperature exposure means they can also be used in manufacture of electric motors, generators, loudspeakers, white goods and lighting equipment.
Loctite® 401, 406 and 454 provide individual characteristics. Loctite® 454 for example is gel and therefore ideal for use on vertical or overhead surfaces. And Loctite® 406 is particularly effective at bonding rubbers and elastomers and even low energy plastics after pre-treatment with Polyolefin Primer. Loctite 401 is considered the general purpose instant adhesive. All can be integrated into semi- or fully-automated production processes for which Henkel also markets a comprehensive range of dispensing equipment.