Plastic Welding

[Rubycon]

Anyone try this or know about it?

Ever break something made of plastic/resin that just cannot be glued back together? The idea is to use a hot tool (such as a soldering iron) to apply heat and fuse the area. It's tricky and depending on the break/plastic type and working load it can be very good to inadequate.

There's commercial machines that do this and even use a filler material as well. Anyone have hands on experience with these?

 

[nonameo]

I saw this done while working construction once. The guy had some sticks of plastic he used as a sort of welding rod. He used a hot air tool to fuse the pieces.

 

[minendo]

JB Weld for the win.

 

[Capt Caveman]

Never knew you could do this. I've always just used epoxy with mixed results.

 

[sjwaste]

Originally posted by: Rubycon
Anyone try this or know about it?

Ever break something made of plastic/resin that just cannot be glued back together? The idea is to use a hot tool (such as a soldering iron) to apply heat and fuse the area. It's tricky and depending on the break/plastic type and working load it can be very good to inadequate.

There's commercial machines that do this and even use a filler material as well. Anyone have hands on experience with these?

I have a deep fryer that filters and drains its oil into a tank. The tank fell once and cracked (oil everywhere, but thats another story). It was cracked, so I used a butane cigar lighter to melt the plastic on the inside and outside of the tub. A month later, still no leaks

I did check to see if the type of plastic it was gave off toxic fumes, which it didn't. Always check that first! I cant recall the type of plastic, but the little recycling code on the bottom will tell you. Google it.

 

[Rubycon]

Originally posted by: minendo
JB Weld for the win.

Epoxy doesn't always work for corners and bosses (things that hold screws or pins). I've exhausted just about every creative avenue with epoxies and they are great particularly the high quality Belzona product line.

Originally posted by: sjwaste

I did check to see if the type of plastic it was gave off toxic fumes, which it didn't. Always check that first! I cant recall the type of plastic, but the little recycling code on the bottom will tell you. Google it.

If it smells good when it burns it's probably bad for you.

 

[sjwaste]

Yeah, in my case I had a crack on the corner, and it needed to be food-grade. Using heat and letting the original material drift back together worked out well.

 

[PottedMeat]

I've fused broken plastic parts together with a few drops of MEK before. The result was surprisingly strong - the joint on my Sony headphones lasted more than a year of heavy use before they snapped again in the same place. At first I used some cheap epoxy that didn't even last a day.

 

[rezinn]

I've repaired cracked hard plastic with a soldering iron with good results. I did not add any plastic, but that would have been helpful but more difficult.

 

[EGGO]

I always thought that if it was put under something that hot, the melted plastic that hardened would be extremely brittle.

 

[novasatori]

on some things that I can't glue usually heating with a lighter or heating a butter knife and using that to soften it, sometimes I can fix stuff...

sure doesn't come out pretty hehe

 

[Jeff7]

What the hell, you don't have a commercial-grade ultrasonic plastic welder right there on the ship? Or sitting next to your computer?


I've used Devcon's Plastic Welder, but it really depends on the kind of plastic. That stuff needs new instructions: "If you survive the fumes from this, you'll love the results." I think it eats into the plastic a bit before bonding it. But it only works on certain kinds. It's great on ABS plastic, but it doesn't stick at all to polyethylene or polypropylene.
And you've probably got better stuff than Devcon's consumer line, such as your Belzona stuff.

Plus, if it's a thermoset plastic, you can't remelt it with heat.

 

[spidey07]

Saw a really cool show on Discovery the other day.

Apparently they use sonic waves to vibrate and heat the plastics via friction to make it fuse. Also called "plastic welds" or "sonic welds". Really cool stuff actually.

 

[Rubycon]

Originally posted by: Jeff7
What the hell, you don't have a commercial-grade ultrasonic plastic welder right there on the ship? Or sitting next to your computer?


I've used Devcon's Plastic Welder, but it really depends on the kind of plastic. That stuff needs new instructions: "If you survive the fumes from this, you'll love the results." I think it eats into the plastic a bit before bonding it. But it only works on certain kinds. It's great on ABS plastic, but it doesn't stick at all to polyethylene or polypropylene.
And you've probably got better stuff than Devcon's consumer line, such as your Belzona stuff.

Plus, if it's a thermoset plastic, you can't remelt it with heat.

I don't have one at my disposal. A fiber coupled YAG laser would probably have some use here. I've tried using 5W 532 but even with goggles it's hard to control and it's like stick welding with 150A fixed current and will burn a hole in your work real fast.

Ultrasonic welding has been around for a long time particularly with plastic goods packaging.

Chemical (solvent) welding is very effective when you use the right stuff. I love working with cellcast (acrylic) using this method. When firepolished, it has the appearance of a solid piece of plastic - very cool!

 

[Jeff7]

That must be the first piece of industrial equipment that you're not already intimately familiar with! :shocked:

What kind of plastic is it that you're working with?

 

[Rubycon]

I've had an interest in it. Looks easy enough to build actually. The hot air concept would work. Styrene is the most common plastic. Kynar and Noryl variants too.

 

[CycloWizard]

Efficacy will depend on the kind of plastic. I did a little bit of this with a lighter when I was young and didn't know any better. Now I know that usually, a welded part will be brittle, have poor adhesion, and heating plastic often gives off toxic fumes.

It can be done safely and effectively, but the heating should be very slow and a low maximum temperature is helpful to prevent complete melting. A lot of polymer rigidity comes from tangles between the polymer chains, which are lost during fracture. Melting two pieces together will return some of the stiffness, but the part will be brittle because the entaglement density will be lower than the surrounding material.

Best method I've found is slow heating with a soldering iron with low heat for some plastics, solvents work for others.

 

[BoomerD]

Originally posted by: nonameo
I saw this done while working construction once. The guy had some sticks of plastic he used as a sort of welding rod. He used a hot air tool to fuse the pieces.

I've seen this a few times over the years myself. Pretty slick set-up they have.

About 30 years ago, I worked on a gold mine project and we installed a few miles of a heavy-wall PVC/ABS pipe. About 24" in diameter. The crews had a surfacing machine that cut and faced the ends, heated the ends up to a melty-temperature, (technical term...look it up) then used a hydraulic press system to push the pipe sections together at something like 3000 psi. Made a VERY nice welded-looking bead joint.

 

[Fenixgoon]

Originally posted by: BoomerD

Originally posted by: nonameo
I saw this done while working construction once. The guy had some sticks of plastic he used as a sort of welding rod. He used a hot air tool to fuse the pieces.

I've seen this a few times over the years myself. Pretty slick set-up they have.

About 30 years ago, I worked on a gold mine project and we installed a few miles of a heavy-wall PVC/ABS pipe. About 24" in diameter. The crews had a surfacing machine that cut and faced the ends, heated the ends up to a melty-temperature, (technical term...look it up) then used a hydraulic press system to push the pipe sections together at something like 3000 psi. Made a VERY nice welded-looking bead joint.

the plastic is heated above the glass transition temperature (amorphous polymers)

you'll also have some degree of melting as well, but that's farther down the line (assuming you have a semicrystalline polymer, which has glass transition and melting)

hooray polymers class

 

[BoomerD]

Originally posted by: Fenixgoon

Originally posted by: BoomerD

Originally posted by: nonameo
I saw this done while working construction once. The guy had some sticks of plastic he used as a sort of welding rod. He used a hot air tool to fuse the pieces.

I've seen this a few times over the years myself. Pretty slick set-up they have.

About 30 years ago, I worked on a gold mine project and we installed a few miles of a heavy-wall PVC/ABS pipe. About 24" in diameter. The crews had a surfacing machine that cut and faced the ends, heated the ends up to a melty-temperature, (technical term...look it up) then used a hydraulic press system to push the pipe sections together at something like 3000 psi. Made a VERY nice welded-looking bead joint.

the plastic is heated above the glass transition temperature (amorphous polymers)

you'll also have some degree of melting as well, but that's farther down the line (assuming you have a semicrystalline polymer, which has glass transition and melting)

hooray polymers class

Hey...that's what I said...the melty temperature...

 

[Indolent]

It will work on these plastics. Won't work on these.

 

[Indolent]

Originally posted by: Jeff7
but it doesn't stick at all to polyethylene or polypropylene.

Random fact: These are the only two types of plastic that float in water.

 

[DrPizza]

Originally posted by: Indolent

Originally posted by: Jeff7
but it doesn't stick at all to polyethylene or polypropylene.

Random fact: These are the only two types of plastic that float in water.

The kind toy boats are made out of and the type that rubber duckies are made out of? Milk jugs, they float too. j/k, I knew you meant "there are only two types of plastic with a density less than 1g/cm^3

 

[rpanic]

Heat up an old flat head screwdriver on the stove and use it to melt the pieces back.

 

[BoomerD]

http://en.wikipedia.org/wiki/Plastic_welding