Welding Plastics ?

Welding Plastics ? >EUREKA<

Hey,
Anyone done any plastic welding..? Need help.. plz..

I can repair some plastics without burning or falling right thro..
Got no tools, cept the hot plastic knife in the end of my soldering iron.

Here is my mission, I need to weld to dissimilar plastics together.
One is polyethylene and the other I dont know.. Its a 20litre plastic oil drum, think it maybe pp or pe, maybe..

Any help would be greatly appreciated..

Cheerz..

 

why not use Silicon instead...

Hot glue gun probably be another alternative.

 

Thanks for the reply.

Silicon does not stick/glue/weld, it is not designed to fuse or bond. Silicon is more of a gap-filler.

Hot Melt Glue, although it is good for a lot of things, most types of sticks are low-temp and become soft at 30degC. It will bond both these plastics but not well enough for my needs.

I need to fuse these two plastics, chemically or mechanically with heat. I could use Hot Glue to finish for some added strength.

Cheerz..

 

i have seen people join car bumper bars with a soldering iron.

If the plastic isn't too think
an old soldering iron should do the trick.
/stops poetry now

i would give that a try if you have a spare old one floating around.

 

I seem to remember that there is some liquid that melts and then joins plastics together. A check around in google should find it.

...
Actually on second thought I doubt that would work for polyethylene.

 

Dissimilar plastics won't weld. You might get a join, but it will be very weak due to not enough molecular bonds. Plus you need a proper heat gun and (idealy) welding sticks. (Yes I weld plastics). The most you might get with the tools you have is a "tack" weld.

The only thing I can suggest is a mechanical bond like nuts & bolts or what Ozdood suggested. Even maybe liquid nails.

 

It's a chemical way that substitutes for the mechanical heat way. If they are dissimilar, then the molecular bonds will still be weak. In other words, they'll stick, but they'll easily snap off.

 

I think the chemical is called Chloriform or something like that.

 

LOL I thought that was a chemical that they used to put people to sleep with before having an operation. Like 30 years ago.

 

Thats right. Also knocks you out. But only in small doses.

 

I think Defiaint can help you out with this one he does do alot of work with plexi and the stuff he uses must be water tight coz he uses it for his res's

 

Cool guys, thanks for all that..

Reaper, u are right of course.
Whatever these two plastics are, they are damn close to the same. I can get a good bond with the soldering iron (~300C), about a 30% to 50% mix of colour (lots of brown, red + black), so there is some mixing/bonding going on, but not every time.

Think I need more heat, say 350~450C, coz I cant get the plasic to pool at all, just a little wetting/sweeting kind'a thing..

If I can get half a join with heat, then go ape with dad's best hot melt glue gun, it might be enough..

Nuts and bolts and barbs and stuff, in brass is going to be like $100..

In the end I may have to go with the old way. Brass theaded tube with nut and plate either side of the plastic, that will like $50..

Its a 40litre pressurised self bleeding airless res, a res for a closed loop..

Cheerz..

 

ok, from what i remember your old hobby (aircraft model) glue actualy chemicaly welds the plastic. also there is a special adhesive that plumbers use for pvc to weld the pipes together.

goto bunnings or reeces and ask for pvc glue its a little jar with a brush. the stuff my mate uses is blue in colour.

that stuff chem welds.

 

As has already been touched upon, solvent welding plastics, where it is possible, uses different solvents for different plastics.

Eg. for PVC, eg. PVC pipe cement, Methyl Ethyl Ketone is the base, whilst things like IPS Weld-on are often based on dichloromethane or other chlorinated solvents, which work well for solvent welding acrylic.

 

Hey Goth, good to hear from u.. I thought u'd be just the person to chat to about this.
Which way would u tackle this..?

Bunnings have a Plastic Body Repar Kit (filler + hardner + a thining agent), Its Syrene based so it will b sticky but may become brittle with age..
There are two type, one heavy duty all purpose, and builders type, 160g/Kg and 30g/Kg respectfully.. The thinner is Methyl Ethyl Ketone + Trolon (?)..

I am thinking maybe another plastic (third type) that may be more conpatable with both the other plastics.
Else I could cut up some spare and weld them (all same plastic) on top of eachother to make like a 'hard point' if u will, a stronger thicker place that I can drill a hole and then tap it to the same thread as a barb.. ??

A piece of PVC pipe 300x560mm would be just the thing, for $0..

Cheerz..

 

isn't 'real' plastic welding just like welding metal? i.e. melt both materials with a heat source, and feed in a filler material in the form of the rod?

A gas torch might be a better choice to provide that sort of heat.

 

Trouble is that it's real easy to overheat and burn the plastic. 500C is like the upper limit of a few plastics, 300~400C for most..
Hot air blower type tools are what is normally used by non professionals. Direct flame is bad.

Its like a secret mystical art, there are some out there who know all about it, but unless u spend like $1000+ setting up and learning there are only little tips and hints here and there..

Styrene and poly vinyl are choice to work with it seems, but it looks like I have ethylene and urethane here.

Finding a solvent has not been easy, like to buy here.

Cheerz..

 

Hot air pvc welding torches are the only way to do this, use parent material for the filler rod if possible, dissimilar pvc's my weld but also may have brittle joins and high failure rates.

I am a plumber who has done extensive pvc welding in industrial applications, pvc , cpvc, polyethylene, darvic, trouvador you name it I've welded it.

Insanely incorrect, pvc welding is one of the highest in carcinogens from the heat process using hot air torches (WARNING: Use correct breathing gear when pvc welding), to use naked flame and actually burn the plastic is sheer stupidity DO NOT DO THIS

You can glue then weld pvc, maybe with the dissimilar materials this may be your best course of action.

 

Yep, thanks for the warning. I knew PVC is nasty, didnt know it was one of the worst..
I am not working with PVC, and that two-part primer / adhesive is just the business for PVC. Good prep' and applied right, in a good temp', and u can do almost anything..

Because of the fumes etc when using heat, I would prefer a chemical solution. Mix, apply, shove it outside till cured..
But I cant track down enough info on what I should be using.
I have some liquid polyurethane, and it sticks to everything under the sun, and sticks good.. But it just peels off both the plastics I am working with..

Almost desperate enough to try 'bog'..

Cheerz..

 

Well I just started building a perspex case from scratch, its going really well, but what you want is to use a proper plastic glue, their about 25 a tube, and set under uv light, work a treat