I have a small bottle with an eyedropper cap. The ‘disc’ part of the cap has become separated from the cylindrical threaded portion, almost halfway around its circumference. What’s the best way to repair it? I have a feeling that plastic cement (‘model airplane glue’) will not make a strong enough bond. And in any case, you pretty much have to go to a hobby shop anymore to get it. I thought of MEK, since I remember my dad using it to do the joints on the ‘spider’ of his swamp cooler. I know there are solvents/adhesives that are used for ABS pipe (and I’m guessing these caps are ABS), but I don’t know what it’s called.
a dab of hotmelt glue.
Not to be a smart A, but wouldn’t it be easier to just get another bottle and refill it?
Plastic cement for models (the “model airplane glue” you mention) will only work on certain kinds of plastics – usually styrene, as that’s the variety of plastic usually used for models. It’s not really a cement per se; it’s actually a solvent (similar to the ABS solvent you mentioned) which melts the plastic a little bit, and effectively welds the pieces together.
So, unless the plastic in your cap is styrene, it likely won’t work. (I’d also bet that the two portions of the cap are made from different varieties of plastic.)
I’d suggest cyanoacrylate glue (Super Glue), particularly a gel or “gap-filling” variety.
I like to fix things, instead of throwing them away. One of my quirks. Also, I don’t know where to get another one; and wouldn’t be inclined to go there if I did.
It was moulded as one piece.