When exposed to UV or visible light, light-curing CAs instantly solidify to a tack-free solid without blooming or stress cracking. Because they require no solvent-borne accelerators to speed the cure process, light-cure CAs will not bloom or crack on sensitive substrates such as polycarbonate and acrylic. Any shadowed areas not exposed to light solidify using the CA's normal moisture cure process.
Low-odor/low-bloom formulations improve the aesthetics of final products by eliminating the white haze that can form on the assembly around the bond line. These adhesives are also free of the pungent odors that can be a safety concern for manufacturers.
Selecting the right instant adhesive
Selecting the proper instant adhesive for an application is critical to the success of the assembly in its end-use application. The selection process should start with answering a series of questions about the adhesive itself, the materials to be bonded, the assembly process, and the end-use environment.
What performance attributes for the adhesive are critical to the end-use application? For example, surface-insensitive cyanoacrylates tolerate acidic or dry surfaces and low-humidity end-use environments. Thermally resistant formulations maintain bond strength at temperatures as high as 250F. Rubber-toughened formulations are crack- and impact-resistant for high-shock/vibration environments.
What substrates will be bonded? CAs easily bond to a wide range of plastics, metals, and porous materials, and they can be used reliably on hard-to-bond plastics with the help of primers that improve bond strength.
Will the adhesive fit easily into the assembly process? Consider the fixture and cure speed required for manufacturing and the dispensing equipment that will be used: manual or automated. By selecting the right equipment, manufacturers can enjoy a highly efficient assembly process, reduced waste, and consistent/reliable adhesive dispensing.
Ultimately, designers who know the basic performance profile for their adhesive -- fixture/cure time, health/safety concerns, bond strength requirements, abnormal stresses, and special end-use variables -- will be able to select the right instant adhesive for their needs.
It's amazing how far adhesives have come, Robert. I was surprised to discover adhesives are used to hold airplanes together. When asked how reliable these adhesives were, I was told that in many cases, the material held together by the adhesive is more likely to tear than the adhesive joint.
Adhesives with a long open time and an instant bond seem to be a great combination. Instant adhesives that stay flexible also seem to be a versatile tool in adhering components. I look forward to using some of these items in future projects.
As an end user of CA glues, and a woodworker, the advances in this area fascinate me. The biggest issue that I and others have had and continue to have with CA glues is that it is difficult or impossible to know which formulation will serve in a particular application. Claims by manufacturers seem to be exaggerated, or at least, only true in controlled situations.
A specific example is the need to bond aluminum or brass to wood or acrylic.
Another issue seems to be shelf life of the opened product and the best way to store opened product. The success of the bond created by CA glues seems to be very dependant on how old the glue is, and how it was stored, once opened.
You might want to try Pacer RX series instant adhesives for your application, or Loctite 406, 401, and 454. Substrates must be clean prior to application...wipe with acetone followed by alcohol as an example. There also must be sufficient moisture on the surface for CA's to work. Problems can arise < 20% and > say 75% relative humidity. Good clamp force and thin bondline is key to CA. Keep your unopened CA in the refrigeraor, and use within a week if at all possible after opening. After 3 weeks I would suggest a new bottle. Hope this helps!
Tks much, Ungarn. I've tried pretty much everything that you mentioned, with mixed results. I will look for the products you recommended. Cleaning and clamping are not an issue. A 3-week shelf life is tough, though. I don't go through even a 2 oz bottle in an average 3 week period. That may well be my problem.
I do put opened bottles in the fridge, but I've always found that a bit contradictory. As you pointed out, CA needs moisture to set up well. And yet, we put an opened bottle into a very moist atmosphere to store it.
Robert, this is not meant to be an advertisement but, one company I consult for uses Henkel products exclusively, specifically 332 Acrylic and 5600 two-part silicone RTV. I can certainly attest to the fact that those adhesives do the job and have reduced our assembly costs substantially. Relative to your blog, it amazes me as to the number of custom products available through Loctite/Henkel. We have found these adhesives meet all of the mechanical and structural specifications our clients have mandated and in some instances exceed those requirements. In all fairness, there are some assemblies that require fasteners that remain operational with temperatures around 650 degrees F. For these applications we still use conventional methods to hold components together but, with improved materials, there are not too many applications that cannot use adhesives.
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