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Plastic welding- PE with PP rod?

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  • Plastic welding- PE with PP rod?

    Just looking for confirmation... Is it possible to weld HD polyethylene with polypropylene rod and a hot air welder? It looks to wet properly, but the joint is shockingly weak so I'm guessing "no". Just looking to repair a cracked wheelbarrow tub and figured I'd ask before tracking down PE rod...

    Thx!

  • #2
    In my experience, no. More than once I've put down a beautiful weld in PP, PE or PVC, only to have the weld peel away with no effort at all. The only thing common was using the wrong rod.

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    • #3
      I had good success with both PE and PVC, but it takes some practise. PVC is the easiest. The problem is getting the base material preheated and up to temp without it saging away or charring. My hot air system is PITA to adjust "just right" because of a long thermal lag, but if I leave it on for a long time before I start the adjustment (air flow) in small steps it can be stable. If you are unsure or can't find the right rod, shear some of the base material into thin strips.

      If you think these are tough try PA66-GF (Glass reinforced nylon - thin wall) fuel tanks on chainsaws. I've done dozens of these and they have to be "right".

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      • #4
        Ok I have to chuckle at this.

        Would you weld cast-iron with aluminum filler?

        No?

        They why would you use a TOTALLY DIFFERENT material when welding plastic?

        ABS, PVC, PP, HDPE/UMHMW, Delrin... Each one is a totally unique material... as different as brass is to aluminum.

        Of course those letters are just the "general" type of material... PVC alone there are hundreds of thousands of types, alloys, blends, mixtures, co-extrusions and unique formulations.

        The closer you get to the original material the better your bond will be. I've used "plastic weld kits" to repair tanks, and they work very very well if you match the material as close as possible. Use the wrong material, you just wasted time and money.
        "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

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        • #5
          Originally posted by Grind Hard View Post
          Ok I have to chuckle at this.

          Would you weld cast-iron with aluminum filler?

          No?

          They why would you use a TOTALLY DIFFERENT material when welding plastic?

          Cast iron is often welded with nickel-based filler metal. Chuckle indeed.

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          • #6
            Yeah, I know they're different but had hoped they were close enough... (shrug)

            I've got another broken wheelbarrow at home, so will likely cut a section of the tub out and use that for another try tomorrow. Just wanted to make sure PE an PP were incompatible before wasting more time on this or junking the hot air welder (have yet to have any luck with it).

            Thanks Guys.

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            • #7
              Originally posted by adatesman View Post
              Yeah, I know they're different but had hoped they were close enough... (shrug)

              I've got another broken wheelbarrow at home, so will likely cut a section of the tub out and use that for another try tomorrow.

              Thanks Guys.
              Just get a piece of high density PE gas pipe, and cut a 1/4" x 1/4" x however long strip.

              Arrange the wheelbarrow so that it is convenient to get at the section to be patched.

              Light the PE strip on fire, and bring it into proximity with the wheelbarrow. Try to maintain the strip burning as you move along the section.

              Invert the wheelbarrow and do the same thing on the other side.

              Works really well for water barrels.

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