I need to attach a plastic piece to another plastic piece. They constitute part of the mechanism of an old music box/caster that I’m trying to fix. I’m hoping to find some goop that I can put between two pieces of plastic so that when it’s cured, winds up holding together as if the two pieces had been welded. One part of it gets a bit of pressure at one part of the cycle, so it has to hold together pretty well. I don’t think airplane glue will do the job for me. Any suggestions? Thanks. xo,
C.
An expert will be able to help you, but you’ll have to tell them what types of platic you’re trying to join. All I know is, if the two pieces are polymethylmethacrylate (the trademark name would be Plexiglass) you can join them with solvent cement – a solution of methacrylate monomer in methylene chloride. This essentially dissolves and re-polymerizes the plastic, making a very strong bond. But any answer will need the type of plastic involved.
what is mentioned is called solvent welding. depends on the plastic if it can be done and what to use. this can be done on small areas and precisely.
some plastics can be hot air welded but this seems suited for some plastics in original construction of an item or maybe repairs like crack filling that is not precise.
If you happen to have polystyrene, all you need is model cement, available from any craft store or Toys R Us model making department.
The more I research this, the more I think I’m just going to resort to some epoxy and learn how to pray.
That’s a pretty safe approach. Without knowing what type of plastic was involved there’s no way to tell what kind of adhesive will work best.
What size pieces are these? Small joints in plastic are weak no matter what you make them out of. Can you add extra material to strengthen the joint?
The problem with prayer is that each type of plastic has a different patron saint.
I’m afraid I might be working with the type that has two - St. Poly and St. Ethel.
Try Devcon two-part plastic welder. Works like a charm.
They actually make nitrogen welders for welding plastic, but they’re used in repairing vehicle parts like bumpers and it looks like they cost $3000. If all else fails you might call body shops and see if anyone local has one and might be able to do it for you. I think the backside of the seam will be ugly though.
Unless,
CMC
The problem is that plastics which aren’t solvent weldable (e.g. Polyethylene, polypropylene) also tend to resist adhesives. Trying to glue, stick, or epoxy anything to those polymers is a fool’s errand. If the pieces you want to join are solvent weldable polymers like polystyrene, ABS, polycarbonate, or such, then your local hobby shop should have something like Bondene which will do the job. If they’re polymers like polyethylene or polypropylene, you need to physically heat the mating surfaces and melt them together. If they’re thermosets, then epoxy/CA might work.
Now, if only someone could figure out how to glue Polypropylene to Nylon…
Epoxy is notably ineffective on many plastics. There’s no good substitute for determining the type of plastic you have, then seeking out the adhesive/solvent that actually works.
How big/complex is the part and would it ruin the restoration if you replaced it? If this is not a problem, do you know anyone who has a 3D printer?
It’s a uniquely shaped, slightly curved piece about 1" x 2". I don’t know anyone who has a 3d printer, but I had given some thought to finding a way to replace it and that method crossed my mind. I don’t know enough about them to consider it seriously, though. I just don’t know how to fashion a similar piece another way. The whole thing starts to become far more elaborate and expensive than I want to engage in, so I’m thinking repair, not replace.
There’s a patron saint of plastic flowers, plastic bags, and don’t forget the First Most Holy Church of Plastic, just for starters.
Best I can tell, it’s probably polystyrene. It’s hard, looks like impact-resistant stuff that’s made into furniture or plastic plates. One component of it appears to have some colored swirls mixed in, and I’d guess it would snap rather than bend if pressure were applied. Does that sound like polystyrene? If it is, what’s the best adhesive?
Sounds like Bakelite to me.
How old is this object?
If it is polystyrene, then you are in luck, because that can be cemented.
Can you post a photo?
Yes - please can you try to post a photo? It sounds like there might be a way to make a replacement. Component.