Welding HDPE?

[Wade Lippman]

I have a Trend AirShield with a broken headband. I have emailed them asking for a replacement, but am not optimistic. I am thinking of welding it. A neighbor has a plastic welding kit he has never used, but will lend me. He does not have a HDPE stick though. In googling, I find two things...
1) HDPE and PP both weld at 572 degrees. He has a PP stick. Can I use that?
2) One reference said you don't need a stick at all; you just melt both sides and push them together.

So, will either of these work for me?P1020146.jpgP1020146.jpg

[Ronald Blue]

They replaced mine promptly a couple years ago. It took two emails but it came quickly after the second one.

[Erik Loza]

I worked in industrial plastics for about a year and we did a bunch of welded projects. Not sure you can use PP stick on HDPE. It "really does matter", IIRC. Personally, I can't imagine that piece mending itself or even being welded and having a long-lasting repair. Not much meat there to begin with. Plastic welding is more like caulking than actual metal welding. In other words, useful for sealing seams, patching holes, etc. Hope you find a solution.

Erik

[Bill Dufour]

Find a scrap of the material. and cut or melt and pull it into rods. That scrap may be a end of the headband that just sticks out of the clamp and is never used until king kong borrows the visor.
Bil lD

[Tom M King]

3m DP100 will glue it back together, but the little duo-tubes of it are not cheap, and you need a special gun with mixing nozzle to dispense it. You can lay a tiny little bead with them. I found the best place to buy the gun is from Golfworks, and you can get the duotubes from a number of places. It comes in clear, black, and tan.

It would be cheaper to just buy another part.

[John K Jordan]

Wade, I've successfully "welded" dozens of things made of a variety of plastics. I use a broad tip on a temperature-controlled Weller soldering station to melt edges of the plastic, sometimes shaving plastic from other areas to act as filler if needed. After "tack welding" the pieces together, I usually plunge the tip into several places to insure good penetration, then add any filler and smooth with the tip. I have one soldering station I use just for this and to pinpoint dents in wood to raise with steam. I don't remember if I use the melt-weld technique on HDPE but I could try it later today if it would help.

For things where strength is more critical, I sometimes melt and join then reinforce with a mesh wrap and epoxy.

I have also used a generous amount of JB Weld to repair some molded plastic things around the farm, such as a tail light housing on the tractor. So far it's held for about 10 years. That did not have a smooth, shiny surface if that makes a difference.

I might not melt with flame since HDPE is highly flammable. Just for information, there is a flame resistant version of HDPE that is green, formulated with some many tiny "chips" of some other substance. I have big sheets of both and I can't get the green stuff to burn like a candle.

JKJ

I have a Trend AirShield with a broken headband. I have emailed them asking for a replacement, but am not optimistic. I am thinking of welding it. A neighbor has a plastic welding kit he has never used, but will lend me. He does not have a HDPE stick though. In googling, I find two things...
1) HDPE and PP both weld at 572 degrees. He has a PP stick. Can I use that?
2) One reference said you don't need a stick at all; you just melt both sides and push them together.

So, will either of these work for me?

[Malcolm McLeod]

I have a Trend AirShield with a broken headband. I have emailed them asking for a replacement, but am not optimistic. I am thinking of welding it. A neighbor has a plastic welding kit he has never used, but will lend me. He does not have a HDPE stick though. In googling, I find two things...
1) HDPE and PP both weld at 572 degrees. He has a PP stick. Can I use that?
2) One reference said you don't need a stick at all; you just melt both sides and push them together.

So, will either of these work for me?P1020146.jpgP1020146.jpg

Lots of HDPE pipe is joined by welding: A heated plate is inserted between the pipe ends; heat is allowed to melt (penetrate) into the pipe a specified distance; the plate is removed and the ends mechanically pressed together, then cooled. I see it done on large pipe (12"->36"dia) with hydraulic jaws doing the mechanical work. The joint is as strong as the base pipe. No welding rod needed.

Mixing types of plastic via welding will not generally end well. There is no poly-linked-chain created. (Once upon a time, I did a lot of HDPE injection molding.)

From the pics, I might be tempted to try glues other recommended, or maybe overlay the break w/ a HDPE 'repair strap' and weld that - - Heat the strap in an oven; when its soft, use a heat gun to carefully heat just the surface where it will overlay (don't let heat penetrate all the away thru - tough to do, I know); then quickly place the strap. Support the underside to prevent it from sagging. ...Not sure i have the patience to execute this, but you may be a better man!

Good luck.

[Tom M King]

I'll bet it's a harness not unique to that hood. Look up face shield parts from welding suppliers. A local welding supply may even have them.

[Mark Bolton]

I have a plastic welder in the box and have used it quite a bit but on very thin parts like that you would have to build up a lot of material around the area and there is still a potential for it not to work. The plastic welding process relies on pressure to make a semi-structural repair so most of the welders have a feed-thru head on them that puts "some" pressure into the weld as you feed the material through the shoe. Oddly most of the instructions tell you repeatedly not to try to melt the base material.

My best repairs have been with reinforced filler rod. I welded a silver dollar sized repair in the bottom tank of my backhoe radiator and its held for years but it was with reinforced rod.

Hopefully you get a replacement. That looks like a poorly designed part to begin.

[Ole Anderson]

As Malcom said, HDPE is fusion jointed every day in the field on sewer, water and gas line projects. I have used it on pipes as big as 16" OD and nearly 2" wall thickness. The two ends are held in a jig and are pushed together hydraulically into a rotating cutter to flatten the ends. The cutter is withdrawn and a hot plate inserted, The ends are then again hydraulically pushed into the plate until the HDPE is heated sufficiently. The plate is removed and the ends pushed together until two beads appear. The pipe is allowed to cool and you have a joint that is 100% as strong as the virgin pipe.https://www.youtube.com/watch?v=wkXXi91NPdQ

So if your part is indeed HDPE (by its looks, I am not sure it is) and you have a clean break that fits together well, nothing is lost by heating both ends until you can push them together to form a bead, and holding it until the part cools.

[glenn bradley]

I have a simple mind. If the epoxy components are not hard on HDPE I would use a bit of resin and fiberglass cloth to repair/reinforce that section. I imagine proper welding would allow the HDPE to retain its flexibility characteristics. I use resin with a bit of flex in it for fiberglass cloth repairs. I have been using the same little "kit" bought at the BORG for many years for small repairs here and there.

[Mark Bolton]

Ive done a bunch of those fusion welds on pipe and the wall thickness is pretty massive for them to work and they are pressed together enough to eat a lot of material (like 1/2" of material is pressed together and rolled) on small diameters and a lot more on large.

Im not sure even with pressing together a small part like that head band you'd ever have a viable repair.

[Ronald Blue]

They had some defective ones that they replaced free of charge. I looked and it was 3 years ago that they replaced mine. I sent the email to info@trendairshield.com. Why worry about welding if they will replace it?

[Wade Lippman]

1) It says HDPE on it.
2) I clamped the parts to a tile and melted a piece from a Swifter bottle marked HDPE into them. It looks atrocious, but actually seems to be holding up. At least for the moment.
3) Yes, it is poorly designed. The replacement part has a lot more material.
4) I emailed them Sunday; haven't heard back from them.
5) I thought about reinforcing it with epoxy putty. I know it won't stick, but might prevent it from flexing and breaking.

[Wade Lippman]

They had some defective ones that they replaced free of charge. I looked and it was 3 years ago that they replaced mine. I sent the email to info@trendairshield.com. Why worry about welding if they will replace it?

I emailed them and got no response in a week. I called them and they say they will send one out. Lets keep a good thought. I returned a lost wallet yesterday; I deserve a break.