Turn signal lens repair, What's the right glue? Options

[bbrock]

I few months ago, I had several tubs of parts take a spill when an overloaded shelf in the garage collapsed. The worst casualty was one of my Hella rear signal lenses. Luckily, it broke cleanly along the glue line between colors. It should be easy to fix, but I'm not sure what the best glue for the job is. Anyone have advice?

[bbrock]

I'm sure super glue/cyanoacrylate would make a fine repair, but I believe methyl chloride makes a superior bond. This is the stuff used to bond plexiglass and I've used it to build water tight aquariums. The trick was figuring out what kind of plastic the lenses are made of to know if this was the right solvent. It chemically dissolves the plastic to allow the polymer chains to dangle free. The chains entangle from both sides of the joint and when the solvent evaporates, you have a strong fusion bond left. I tried breaking my test lens and couldn't. Just tried the same with the cured good lens and the weld is so clean, you'd never know it was ever repaired. Here are a couple pics of the repaired lens, including one with a gallon of vinegar (about 8 pounds) right over the weld. This is being supported by the mount studs, one of which is also solvent welded back on.