Repairing (adding to) plastic

[Edward B.]

I've been working on the rear defroster on my 69, and you can see from the attached picture that my upper duct is broken and even missing a small chunk of plastic at the edge. (Compare my duct on the left, with a picture I found on the internet showing what it "should" look like on the right.)

I've repaired cracked plastic before using various glues, but I've never tried to ADD plastic to "build up" a missing piece. Does anyone have any hints or suggestions they can pass on? I'm assuming I'll have to use some kind of epoxy and make a form to build up the plastic, but I'm a little lost on this one.

Thanks
Ed

[Mark S.]

Re: Repairing (adding to) plastic

Ed:
Others can chime in; however, I have had good luck using plastic epoxy, a 2 part product, to repair and build up broken plastic pieces. The epoxy can also be colored by using colorings for fiberglass from companies in the boat industry. Mark

[Edward B.]

Re: Repairing (adding to) plastic

Thanks Mark. I found a few sites that recommended JB Weld PlasticWeld (their part number 50132), so I may give that a try.

I found a TON of sites that show how to repair cracks, but only a couple that showed how to build up missing pieces. One of them said to use hot glue sticks and fill in the void, but I'm not sure that would actually work. Another showed how to "weld" a new piece of plastic to the old broken piece using a soldering iron, but it didn't look that good once it was done.

I have a feeling this is going to be difficult. Especially since I want it to turn out so you can't tell it's been repaired!!

Ed

[Mark S.]

Re: Repairing (adding to) plastic

Ed:

There are other manufactures of the plastic epoxy as well. I had a plastic fan shroud that had a chunk missing out of it. I used the plastic epoxy with black fiberglass coloring to mold and fix it. You could not tell where the fix was; and the Corvette passed the judging process. Best of luck!

Mark

Mark

[David J.]

Re: Repairing (adding to) plastic

Ed;
I work with plastics a lot, mostly ABS and Acetal (Delrin). The first thing I would do is try to determine the type of plastic you are dealing with. Some types are much easier than others. The easiest to work with, and the most common in some cars is ABS. This is the same plastic used in most models. If you have any model glue or plumbing glue for ABS, try putting a drop on a hidden area of the part and letting it dry. If it will not scrape off it is indeed ABS. If it flicks off it's something else. The next easiest is HDPE. It can be joined best by melting, or specialty welding. You can then lightly machine it to the desired shape. If it is a form of Acetal, nothing will adhere to it.

[Edward B.]

Re: Repairing (adding to) plastic

David, I have some of the ABS plumbing glue so I'll give that a shot this afternoon and let you know the results.

Mark, JB Weld has the same thing in a putty, so maybe I'll give that a try. Did you make any kind of form or did you just eyeball it?

Ed