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I have been reading up on cyanoacrylate, commonly sold in the US as "Krazy Glue" or "Super Glue", because I want to to use it to repair small plastic parts on either toys or appliances, due to its strong hold and quick setting time.

However, I have heard that these types of glues will "melt" or otherwise dissolve certain types of plastics. My research on whether or not this is an actual chemical reaction between the compounds has been inconclusive. I do not see anything listed under properties or uses on Wikipedia, nor do I see any specific mentions or warnings on the product page for Krazy Glue.

Though it works with most, Krazy Glue cannot bond all materials. For best results, please do not use on paper, foam, rear view mirrors, polyethylene, Teflon® or other fluorocarbons.

So plastic is no mentioned either way which leads me to the question:

Will CA glues damage plastic1?

1 - I understand there are probably many types of chemical compositions for plastic, however I do not have a specific one in mind when asking this question.

  • The reason the label says "don't use on Teflon" is because nothing sticks to Teflon. – Mark Apr 7 at 20:04
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It's not likely, but first let's talk about "plastic".

There's two main kinds used on toys are PVC (polyvinyl chloride) and ABS (Acrylonitrile butadiene styrene). PVC is a bit flexible, and ABS is the rigid stuff (used to make harder shells, smaller children's toys, and stuff like LEGO blocks). You can generally tell something is PVC if it has a little bit of a give, or you can dig your fingernail into it slightly.

Either way, most people I know consider super glue a safe fix for action figures and other toys. Aside from repairing them, some will apply a small amount to ball/socket joints to stiffen them up, or on top of custom paint jobs to act as a sealant.

Permabond, an adhesive company, even suggests that cyanoacrylates are ideal for PVC and also for ABS. However, ABS tends to me smoother and breaks more cleanly, so it may not be effectively bonded by super glue.

One thing to note about cyanoacrylates is that they have pretty low shear strength, which means if you're applying them to a part that's got movement, especially one that can be twisted, then the repaired piece is likely to just twist off.

An alternative is to use two-part epoxies, such as Devcon. They'll bond PVC and ABS both. However, they take a bit longer to dry and cure and they also have terrible fumes while they're being mixed, so you need proper ventilation. This bonds become much more durable to all types of pressure and use. They have not yet, in my experience, damaged a plastic.

Another alternative for ABS plastic is to use a plastic weld solvent, such as bondene or plastruct brand. These solvents actually bond the separate parts together using a chemical reaction that fuses a thin layer of each part together. So, it's making the two broken pieces one fused piece, instead of two pieces with an adhesive between them. This is the same type of substance that toy manufacturers use when they are sealing toy parts together (such as the front and back of a figure's chest, or either half of a toy gun). This bond is fairly strong, and generally needs high pressure and some heat to break.

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  • Good answer, just a note to expand on it. There are also other kinds of plastic commonly used for toys and household items, like polystyrene, polycarbonate, polypropylene, acrylic, urethane, etc. There are some special cyanoacrylate formulations that do a better job on plastics in general and are sold for that purpose. Certain plastics like polyethylene I don't think can be glued with any variety, and polypropylene may be in the same boat. (cont'd) – fixer1234 Sep 1 '19 at 0:57
  • But also be aware that it can damage some plastics, in a different way than suggested in the question. I'm not aware of plastics being melted or structurally damaged, but some plastics are etched by the fumes. So the item appearance can be damaged by vapors from the glued location. – fixer1234 Sep 1 '19 at 0:57
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Might i add an experience i had: i once had a cheap watch of which the plexiglas front shell came off. I glued it with cyanoacrylate glue and at first it was fine. Next day, it seemed the fumes of the glue had affected the inside of the plexiglas front and it became all white instead of transparent. I had to throw away the watch...

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