Patching A Small Hole In Plastic Case: What To Use, Please ?

[Bob]

Hi,

Have a "patching" job, and not sure what to use. Would be most grateful for any suggestions.

Had to take apart a kids toy, plastic housing, to fix the motor inside.

They glued the housing, no screws, so the case is now fairly "butchered," with some cracks, etc., as a result of my taking it apart.

I can use epoxy on the cracks just fine, but the case now also has some approx., 1 inch (some 1.5 inch) holes and cutouts.

Epoxy doesn't seem correct for this, as I think it's too big a space to cover.

I can put a piece of wood behind the hole when I'm patching it to give some grab to the patching compound, and minimize the depth of the hole.

What should I use other than epoxy for these "holes" ? Again, it's a plastic case.

Would want it to "set-up" Hard (like epoxy would)

Any other thoughts on doing the patching would be most appreciated.

Thanks, Bob

[Frank]

Not all plastics are alike. If your plastic is polyethylene, nothing will stick to it.

I might try a hot melt adhesive with mechanical patch like piece of fiber glass.

[Mayayana]

That's a tricky one. Perhaps buy the child a horse and hope they forget that you broke their toy? :)

I can think of a couple *possibilities*, but nothing that's clearly the best solution:

• A fiberglass patch kit... if it doesn't melt the plastic.

• A flexible patch attached with contact cement.

[Mike Duffy]

Just use expoxy then. Apply in several sessions, each one putting a new layer as thick as can support its own weight while soft.

[Jerry.Tan]

Considering the kind of guy he is, he'd probably buy this child a broke horse too!

[clare]

First things first - what kind of plastic? In many cases the simplest way is to get a peice of the same type of plastic and either heat or chemical weld the patch back in. ABS is a cinch. PVC not a whole lot worse. Polyurethane isn't bad either. Polyethelene is also quite simple to "weld"

[dadiOH]

Assuming epoxy sticks to it, just use that but thicken it so it doesn't run. A good thickener is fumed silica (trade name Cab-o-sil or Aerosil). It is a very, very fine white powder, turns more or less clear after mixed in; add it to some uncatalyzed epoxy, stir til well mixed, add more of it or epoxy as needed to get a spreadable material (about like vaseline or peanut butter), then catalyze and mix well. You can add some mechanical strength by tapering the hole edges at an angle on both sides with a file.

If you use wood to back it up you won't get the wood off after the epoxy sets up; if you want to be able to remove the wood, put a piece of clear packaging tape on the epoxy side, and all will peel off easily.

[Frank]

Of course. I worked enough on plastics to identify most without the use of a lab. Most of the cheap stuff is PE which is hardest to repair.