Common and bizarre uses of cyanoacrylate adhesives
Permabond 910 is the original cyanoacrylate, and as we celebrate the 65th birthday of 910, which was designed for bonding, I can’t help but think of all the other ways cyanoacrylate adhesive is used. I am certain that 65 years ago it would have been difficult to image the large variety of cyanoacrylate adhesive types available today, but I expect it would have been impossible to imagine the applications. For example, 65 years ago the thought of a 3D granular printed piece being infiltrated with cyanoacrylate would be inconceivable. Similarly the fact that we modified formulations to resist up to 480°F so that cyanoacrylate could be used to bond components onto flip chip computer boards, or bond the key pads on mobile phones, or perform laparoscopic surgery, or…
Following are some common uses of cyanoacrylate that have come to pass due to our customers’ unending creativity and our technical staff’s unrelenting curiosity.
Crime Scene Investigation: Often finger prints left at a crime scene are not visible impressions that can be photographed. Invisible finger prints are called latent prints. So how does cyanoacrylate adhesive make latent prints visible and useful to law enforcement? Cyanoacrylate adhesives are incredibly reactive liquids – they wouldn’t be liquid if they weren’t stabilized. Very small traces of moisture deactivate the stabilizer and allow the adhesive to cure. Small quantities of curing adhesive can volatilize and then fall back to the surface, creating a blooming or frosting effect. For most customers, this is unsightly- and we’ve gone to great lengths to create a low odor, non-blooming line of adhesives. For crime scene investigators, it is this otherwise undesirable feature that creates the print. Standard ethyl cyanoacrylate adhesive can be used, but for maximum print visibility and maximum speed of developing the print, Permabond formulated a specialty grade for law enforcement. To learn how to collect finger prints with Permabond special high bloom grade CPP621 click here.
3D Printing Infiltrating: Granular 3D print methods produce 3D printed components that remain powdery and fragile unless they are coated. To improve their appearance and strength they are dipped into cyanoacrylate adhesive. The adhesive infiltrant wicks into the porous model and cures to a hard solid piece. Unlike the crime scene cyanoacrylate adhesive, 3D print infiltrants need to be very low odor with low blooming effects. Depending on the type of printing various products are available with ultra-fast cure, high gloss surface, fast cure with good penetration and brilliant color, and a delayed set product which provides maximum strength and a matte surface. (Link to 3D infiltrant 031616)
Under Water Bonding Many years ago an organization I can’t mention contacted Permabond to bond something I can’t talk about to the bottom of an item that was in the water. Chemists brain stormed and all agreed that there was no solution – at Permabond that is when the fun begins. Tip – if you want to get something done, simply tell a chemist it isn’t possible. The solution was a surprise… cyanoacrylate! We thought they had gone daft. How can you bond something underwater with a product that cures with water? As it turns out, if you put a glob of a high viscosity adhesive onto a part then put it under water it will immediately form a shell of cured adhesive on the surface – but the adhesive under that shell will remain viable longer. Once under water, smash the part with the glue glob on it to the boat so the glue shell bursts, and the liquid inside it can bond the two components.
Coral: Cyanoacrylate adhesives cure with moisture but the cured adhesive isn’t incredibly resistant to water. However in many applications like the one above, long term bonding isn’t required. In the adhesive business we call bonds that must perform with long term water contact “fish tank” applications. We never recommend a cyanoacrylate for a fish tank application – but wait – cyanoacrylate adhesives are used to bond coral into fish tanks all the time. Cut branches of hard corals are glued onto a piece of reef coral, again this is often done in the tank. The new piece of coral is held in place while it sets it’s “roots” through and around the cyanoacrylate; by the time the adhesive dissolves the living coral is firmly attached to its new home.
Fixturing: Cyanoacrylate adhesives are desirable because they are single component, instant curing, non-flammable, and bond most materials. When given the option between this simple solution and an adhesive that needs mixing, heating, a two step process, etc… most prefer cyanoacrylates. But cyanoacrylates do have some limitations; let’s have a look at them:
- Solvent resistance – cyanoacrylates have good resistance to non-polar solvents such as gasoline and motor oil but poor resistance to polar solvents such as water and acetone.
- Temperature resistance – depending on the type of cyanoacrylate (methyl, ethyl, alkoxy alkyl etc…) maximum temperature resistance ranges from 85°C (185°F) to 250°C (480°F)
- Cured state – although the temperature resistances listed above are quite high, keep in mind that cyanoacrylates are quite brittle and may not withstand movement between substrates with different coefficients of thermal expansion if temperature variation is expected.
- Gap filling – Cyanoacrylates are not designed to fill large gaps.
Because of their brittleness, cyanoacrylate adhesives aren’t generally recommended for structural applications. Nevertheless, they are used in processing to off-set the slower cure time of other adhesives. How does this work? Many applications that require the structural toughness and durability of, say, a two component epoxy benefit from also using a cyanoacrylate. The parts are assembled with the two component epoxy and also tacked together with a cyanoacrylate. This eliminates the need for clamping or jigging as the epoxy cures, because the cyanoacrylate is holding it fast in place.
Similarly cyanoacrylates are used to hold o-rings in place during shipping. In many applications the o-rings are bonded in place. In other applications the o-ring will be in compression in the unit so the cyanoacrylate isn’t required to maintain the o-ring’s position during the rugged equipment use or underwater, but is used to prevent the manufacturer from receiving complaints due to the o ring being lost in transit or forgotten in assembly.
While on this topic – many folks form o-rings by splicing and bonding with cyanoacrylate. Yet another clever use.
Tacking: Wire tacking and strain relief are common applications for cyanoacrylate adhesives in everything from speakers to motors to electronics. Again cyanoacrylates cure by reacting to the traces of moisture on the surface they are bonding. When used in tacking applications, an accelerant or setter is used to cure the surface.
Medical & Veterinary Uses: In addition to suture replacement, there are many surgical uses of cyanoacrylate – absorbable grades are even used to advance medical technology. Butyl cyanoacrylate is used extensively in veterinary medicine for surgical wound closure and to close the wounds from cat declawing etc…
Cosmetic: Cyanoacrylates are used for bonding fingernails and eyelashes.
Woodworking: Cyanoacrylates are commonly used to bond the pads of clarinets and saxophones, as well as to produce the shiny finish on guitars. The adhesive provides specific acoustic benefits to the wood.
Although 910 is still a flagship, super strong, methyl cyanoacrylate, there is a large variety of other types of cyanoacrylates available today. So which are used for what types of applications?
Methyl Cyanoacrylate – 910 is a pure methyl cyanoacrylate which forms strong bonds to metals
Ethyl Cyanoacrylate – there are several types
- General purpose ethyl cyanoacrylates are ideal for plastic bonding. Special grades are available for elastomers.
- Toughened ethyl cyanoacrylates are less brittle and provide more impact resistance than general purpose ethyl cyanoacrylates.
- Surface insensitive ethyl cyanoacrylates are ideal for acidic or porous surfaces.
- Modified ethyl cyanoacrylate adhesives resist higher temperatures
Butyl Cyanoacrylate – Medical and Veterinary applications
Octyl Cyanoacrylate – Medical applications
Those are the common straight chain cyanoacrylates, however the possibilities expand when we take side groups into account. Alkoxy alkyl cyanoacrylates can provide additional benefits such as low odor, low bloom, and increased flexibility, and are used in a variety of applications.
Do you have a unique bonding requirement? Please let us know if we can assist you.