Plastic Welder - anyone used?

**evandude** · 01-08-2006, 10:49 PM

Has anyone here ever used a plastic welder?

the one I have in mind is this:

http://www.harborfreight.com/cpi/cta...emnumber=41592

it's basically a hot-air pencil, you just give it compressed air and power, and then use it with narrow plastic welding rods, and supposedly other than that it's similar in concept to metal welding.

I have heard that that particular unit isn't great but works, supposedly it runs hotter than it should for plastic welding because it has no temperature control. Not surprising, i mean it is $35 and "real" ones are way more than that. I am not going to let that stop me if it's otherwise feasible, if need be I am comfortable making an add-on temperature controller with a thermocouple, as long as it's not a waste of time.

I am just wondering how much of a pain it is to do plastic welding, and how well it works. My real motivation is trying to bond polypropylene to ABS or other plastics, since PP resists pretty much all common solvents and glues, but it is a thermoplastic so it can be bonded with a high-temp welding method such as this.

Most important question is, would PP and ABS actually bond if they were both melted? I will test this myself when I am home again with my big heat gun, but maybe someone with more experience knows off the top of their head. Since a normal glue won't stick to PP because it can't break down the plastic structure at all to attach to it, it seems that melting the plastic should be successful, but that's assuming that the PP won't just solidify again without bonding to the other plastic at all. Most of the information I have found by googling thus far has suggested that this hot gas plastic welding is suitable for all types of thermoplastics, but they don't specify whether that means bonding only like plastics, or whether you can bond any thermoplastic to another.

If it is possible to bond the dissimilar plastics, is plastic welding a viable solution for actually doing some of the "molding" process of installing a dash LCD, or is it really only suited for just attaching the two pieces together? One thing I would worry about is warping the LCD frame with excessive heating over a larger area, like if trying to fill in a gap with plastic.

**blk02si** · 01-09-2006, 02:15 AM

Ive used plastic welder 2 part epoxy, it has a 5000 lb per sq inch hold. could never break it. Ive never seen a tool like that picture though. Sounds neat

**evandude** · 01-09-2006, 08:50 AM

Originally Posted by blk02si

Ive used plastic welder 2 part epoxy, it has a 5000 lb per sq inch hold. could never break it. Ive never seen a tool like that picture though. Sounds neat

Unfortunately, that "plastic welder" epoxy still relies on solvents to bond to plastic, and isn't compatible with polypropylene according to the datasheet. Like everything else I've tried, it will just peel right off like it was put on teflon.

**GnatGoSplat** · 01-09-2006, 09:39 AM

Just out of curiosity, but why weld polypropylene to ABS? Why not weld ABS to ABS?

**evandude** · 01-09-2006, 10:15 AM

because the center console in my car is made out of polypropylene. Believe me, after all the headaches of trying to deal with the polypropylene, I wouldn't be using it if I didn't have to.

**DeltaFX** · 01-09-2006, 11:12 AM

Correct me if I'm wrong but can't PP be glue if shortly flamed before ?

**Scouse Monkey** · 01-09-2006, 11:19 AM

quite possibly yes. it is all about free surface energy. the only way you could melt weld PP and ABS is a mechanical mixing at the surface. they will never actually combine so when welding them make sure there is some physical interaction by poksing at the plastics to get them to physically mix and the polymer chains to entwine. A slight stabbing action with a pin or flat rod on the end of the welder should help a lot.

**evandude** · 01-09-2006, 02:40 PM

Originally Posted by DeltaFX

Correct me if I'm wrong but can't PP be glue if shortly flamed before ?

That's a good idea, I had pondered something along those lines before. I read some information about some australian company pioneering a method of chemically treating the surface of PP so that it could be bonded to, however there was no specific information and seemed like an industrial process way out of reach of a hobbyist. Naturally i wondered if there was any way to treat the surface myself, but that got me right back to the original problem of finding some solvent or other chemical that would actually react with the plastic. I didn't think of just blasting it with fire

hopefully that would disturb the material at the surface enough to bond. That's another thing I'll have to try when I go home. That would sure solve all my problems, being able to just take a little butane torch to it for a bit... I'll keep my fingers crossed!

**turbocad6** · 01-09-2006, 02:58 PM

check out this company, I use there products... there airless welder is a fancy temp controlled soldering iron.... you can do the same with a butane soldering iron.... they sell rods that are compatable with pp as well as a universal ribbon...... there is a lot of info on there site too..... the air welder isn't a good idea for precision work like this,, go airless......

**evandude** · 01-09-2006, 04:29 PM

Cool, I might have to do some experimentation with that as well, I happen to have a large-ish 45W soldering iron at home that I could test out, not as well-suited as the real thing but it should give me an idea of whether it's possible/feasible to bond the materials this way.