Glue/Epoxy for plastic?

I have a headlamp surround that develops a crack in the same spot so it's under a bit of stress. I have tried epoxy a couple of times but it eventually lets go so I'm not using the right product. It's not ABS plastic but I don't really know the type of plastic.

Any suggestions?

Thanks.

Bob S.

 

Try Devcon Plastic Welder.

Remember the three little words:

"Prepare the surface"

More important than which product you choose.

 

I'll look into that one. Have you used it?

I believe my prep work has been proper but I'm thinking I need something that creates a melting bond?

Bob S.

 

I've used it many times and it works well in many applications but...................

Not every plastic will "melt" so you may only get a mechanical bond. The strength is directly related to how much surface is involved (cracks in thin areas are weak). If you can back up the area with a "splint" it will be much stronger. As a rule glue doesn't stick to glue so any old repair has to be completely removed.

 

I use Devcon Plastic Welder in repairing shock actuators, works well on that plastic.

 

I have good luck in plastic repair with epoxy. However the cracks are widened up to 1/32 to 1/16 inch with a dremel tool and bit so that the epoxy has somethign to bite into and hold.

The fact that the plastic cracked is prima facia evidence that insufficient amounts of the stuff were present before hands. So, use common sense and repair the crack, AND add backing material (even brass/steel tube/rod) so that the part has teh substance to deal with the stresses.

many of the plastic pieces can be fixed with modeling cement, the liquid brush on kind (basicaly MEK and acetone).

 

I think reinforcing it might work but just gluing the crack certainly won't. The last time I had about 1/8" of epoxy spread over the back side but that didn't work. So maybe a piece of plastic as reinforcing which is applied with the Devcon will do the trick this time.

Thanks for the tips guys.

Bob S.

 

I have had some luck melting/welding plastic together with a soldering pen, that is where it doesn't show.