One common complaint we hear from people who avoid restoring cars built from about the mid-1970s on is that those cars contain increasing amounts of plastic - plastic interior trim, plastic bumpers, plastic engine covers - and that repairing automotive plastics is impossible. Yet, as we see from all those plastic welding setups advertised in our favorite restoration supply catalogs, fixing broken plastic pieces is absolutely possible.

Not only possible, but it's also possible to do without those setups, which can sometimes cost big bucks. In fact, repairing plastics can actually cost next to nothing. I'd read about the solvent-welding technique in the past - in fact, Scotty Lachenauer wrote a good article on solvent-welding plastics back in Hemmings Sports and Exotic Car #59, July 2010 - but a more recent post on Hackaday persuaded me to investigate the process a little further. As it so happened, I had a broken piece of A-pillar interior trim from one of the HMX's donor cars (as seen above), and I had committed to giving a presentation on automotive plastics repair for our most recent Hemmings Mediterranean cruise, so I gave the process a shot.

Step one is identifying the plastic. There's all sorts of plastics out there, and they all respond to different solvents. Urethane Supply Company has a pretty comprehensive guide to identifying plastics, should the piece you're repairing not have any identification marks on it. Plastic interior trim is more likely than not to be some sort of polyethylene, such as HDPE. Once you've identified the type of plastic, round up some scrap plastic of the same type. Fortunately, I had another broken piece of interior trim from the same car in the same nutmeg color.

Next, you'll want to find a solvent that corresponds to your particular plastic, which may take some research. Nerf gun modders have actually put together an extensive list of which solvents work on which plastics, but if you're in doubt, common acetone - available at any hardware or home improvement store (look in the paint supplies aisle) - seems to work on most automotive plastics.

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