Easy to use and automate, instant adhesives -- also known as cyanoacrylates or CAs -- are one-part materials that cure in seconds at room temperature when compressed between two parts and exposed to ambient surface moisture. These adhesives provide high bond strength to a variety of substrates, including PVC, ABS, polycarbonate, phenolic, nylon, steel, stainless steel, aluminum, zinc dichromated metals, wood, cork, leather, fabric, paper, nitrile rubber, and neoprene. They also work on hard-to-bond plastics such as polyolefins, polyethylene, polypropylene, fluoropolymers, acetal resins, and PTFE.
Available in a wide range of viscosities from water-thin wicking grades to gels, instant adhesives are a natural choice for high-speed assembly applications that require an extremely strong bond in seconds. Processing can be manual, semi-automated, or fully automated, and formulations are available to meet most performance requirements.
Instant adhesive provides an extremely strong bond in seconds on close-fitting parts.
Since these adhesives provide long open times before substrates are mated, components do not need to be joined immediately after the adhesive is dispensed. Instant adhesives are especially valuable when bonding small parts or filling gaps of 0.08 inches or less.
Manufacturers in a range of industries trust instant adhesives every day to meet their design and assembly challenges. These adhesives perform reliably on automobiles, appliances, medical devices, electrical equipment, electronics, cosmetic packages, toys, lighting fixtures, motors, generators, compressors, filters, and a range of other applications.
Early generations of instant adhesives exhibited some inherent limitations such as poor peel strength, a limited ability to cure through gaps, an inability to survive exposure to elevated temperatures, stress cracking on some plastics, strong odors, and blooming -- a white haze that forms along the bond line. New technical advances in CAs have overcome some of these limitations for challenging applications.
Instant adhesive varieties
Many varieties of instant adhesives have been developed that overcome traditional limitations and meet design and assembly challenges. For example, chemical innovations have resulted in surface-insensitive formulations that cure rapidly and fully on acidic or dry surfaces and in low-humidity environments. The latest surface-insensitive formulations speed assembly processes by fixturing in 15 seconds or less. These varieties also provide high bond strength and thermal resistance, maintaining their strength at temperatures of up to 250F. Surface-insensitive CAs bond metals, plastics, and elastomers.
Toughened formulations contain additives that increase the adhesives' crack and impact resistance, allowing their use in high-shock/vibration environments. Toughness is the ability for an adhesive to resist cracking, and it is not related to flexibility. In their cured state, new toughened polymers exhibit more peel strength than older formulations, and they are far less brittle, greatly increasing the adhesives' usefulness in sporting goods and other equipment designed for high impact.
Flexible instant adhesives are commonly used in joints that must stretch or bend -- for example, on catheters. These products greatly reduce knife edging, which happens when the sharp edge of the cured adhesive cuts into a soft and flexible substrate being bonded.
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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