Plastic Fender repair

[tungularafishcamp]

Haven't figured out how to tell what type it is but have been able to weld most types(some needs more heat) by just experimenting and taking a piece of the same material from a out of the way spot to use as rod.
Rick

 

[yomax4]

There is a company called Steinel. They have great heat gun type plastic welders and rods. look them up and they have a cool burn test to determine what type of plastic you have. If I remember right ( because some rods work for other plastics ) there are only 6 options. HDPE, LDPE, High or Low density polyetheylene < most atv plastic. PVC and a couple others. Check it out.

 

[Danno1]

OK dumb question.Anyone have a fool proof (fool being me) of figuing out what kind of plastic that I'm looking at...This haunts me all the time.

........Just wish I could figure out the unknown types that come on consumer/commercial applications...ie vehicles and equipment.

Plastics Identification 101.

Cut off a small sliver and light it on fire. Observe the flame and smoke.

PVC- blackish smoke and acrid smell
Polyethylene(PE, HMWPE, UHMWPE)- no smoke, material drips like a candle and smells like wax
Polypropylene- no smoke, material drips like a candle and smells like burnt oil
Polyamide (Nylon)- no smoke, pulls to form thread, smells like burnt horn
Polycarbonate- yellowish sooty smoke, sweetish smell
ABS- blackish smoke, soot flakes, sweetish smell


ABS also comes as an alloy mixed w Polycarbonate. It's trade name is Kydex. It's used a lot for vacuum formed products. Fenders and hoods might be a good example.

.

 

[joes_427_vette]

Years back they were pushing plastic welders. A short time later it was V out the front and back, use a epoxy glue like JB Weld with plastic screen door material ar a reinforcement. The second method worked much better on the tears of plastic bumper covers. It doesn't sand too well so be careful how much you apply. A heat gun will normally get the plastic back in the formed shape if needed.

 

[pdowling1]

Most items will have a mark on the backside somewhere identifying what they are made of, just like plastic bottles (This is used in recycling). The JD fenders are marked HDPE if I recall. I have welded several of them using a soldering iron.

 

[handirifle]

If the crack is in a stress area, you want to reinforce it? I always weld the crack and then an overlay that goes well past the original crack. That takes care of the brittle area next to the crack. Reinforced like this, I have never had one re-crack, at least not in the general area of the crack.

If it's in an area that won't be seen I'd weld the crack and then do the JB Weld trick over it. That stuff is nothing short of amazing. I have glued so many dissimilar materials together, and it holds like steel.

Heck, on an old XL600 honda I had, the master cylinder fluid level window was cracked and leaked around the edges as well. Only used ones were available, so I JB'd it. NEVER leaked a drop after that. And the brake fluid didn't phase it. But on stuff like that, you must keep in a warm place to fully cure for 24hrs or so before using it.

 

[2TALLTARY]

ABS is a great machinable plastic along with delrin. I've used abs to make everything from stands to doorknobs. Delrin is the best machinable plastic around. Very strong, durable and long lasting. Try Your Source For Plastic Sheet, Slab, Rod and Tube. 866-832-9315

 

[varmint]

Didn't see anyone already mentioning it, but Harbour Freight sells a plastic welder (air w/ heat) that I am told works pretty well for the price: I think you can get one for around $50 or so on sale.