What's the Best Way to Weld PP Sheets?

Polypropylene is b*tch to stick to anything. I'd suggest mechanical fixings.
I'd also ask why PP????

Del

Customer makes GF PP Twinwall sheet only, and wants to have his sheet fixed against a wall.

A but joint in thin sheet would not be possible in ultrasonic as it will very difficult for you transfer the force to weld in long and thin sheet.yes it may work if its lap joint.However more amount of GF will deteriorate the weld quality.

For laser weld in plastic I have no experience.

Regards

By the way how thick is sheet?

Good catch...it's 10mm twinwall PP sheet (X structure)

Then how about cutting sheet an oblique sections at 45⁰,matching there sections and weld like lap on ultrasound, some support or anchoring can be provided to avoid the lateral movement of sheets.

Its like a 50% lap and 50% but jont

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You mean like welding a PP strap across the joint?

yes isn't that what you are looking for ?

Sorry I guess u misunderstood you in previous reply. its not the straps, you can do this on sheets directly as shown in pic.

I see now... this method gives indeed a very nice joint, but what if these sheets are a little bit slunt? A strap may conceil imperfections.

OMG I had to look that up: seems a bit strong for a poor old sheet of plastic.

If a strap is acceptable: then ultrasonic sounds () good.

We joined PP sheet by using a hot air jet and filler rod to make PWB fab equipment.

Never tried to weld that stuff GF you're using.

V-notch the joint and lay beads in till flush, then trim.

Suggest you use liquid fiberglass to bond both glass fibre reinforced PP sheets by preparing first both side for bonding, provide fiberglass fibre for extra reinforcement and afterwards apply heat by blower to cure.

Have you considered hotmelt adhesive glue joint. Works well with PP.

Any companies, brands you can recommend?

Poly Pro sheet with glass reinforcement cannot be extrusion welded. We weld plastic sheet together all the time, but avoid anything glass reinforced.

You can weld PP sheets with a hot air gun and PP rods in the same way that you weld PVC but at a higher temperature. This type of welding is normally done for sheets up to 2 mm.

For 10 mm sheets you should use what we call an extruded welding. The sheets edges are milled at 45 degrees .The 90° channel formed by putting two sheets together is filled with PP which is extruded into the channel. This system too works with hot air.

Extrusion machines for this application are available on the market and not to expensive, but you need some experience to do the job. This is the best solution for tanks when you need a perfect water hold.

It would be good to know the application. Does it have to be air tight, does it have to hold water or hold steam.

Ultrasound is also a solution but is normally used for small surfaces. Transductors are very expensive.

The sheets edges are milled at 45 degrees .The 90° channel formed by putting two sheets together

Like this?:-

How clean (neat/tidy?) can the resulting joint be made?

"How clean (neat/tidy?) can the resulting joint be made?"

A skilled operator can make an almost invisible joint, usually by slightly overfilling and trimming back to flush.

Post #14 says this won't work on GF materials, but #17 says it will.

I can imagine that trying to weld filled material would be more difficult.

Cheers

Your drawing is exact. The appearance of the welding is like a MIG structural welding on steel but much smoother.

In industrial applications like galvanic tanks there is no finish requirement so it is left as it appears (quite neat if you have a good hand)

In applications like steam cabins for Turkish baths, the welding is grinded off flush to the surface and then polished.

Hang on I believe I wasn't clear enough. Here's the better storry:

10mm Twinwall sheets (20% Glass fibre reinforced) need to be installed into the inside of a lorry used for raw meat transportation. I'm looking at following:

a) install the sheets side by side and weld these together to end up with one large surface.
b) install the sheets side by side leaving a gap for expansion/contraction of the sheet, then weld/bond a PP strip across the sheets to hide the gap.

The sheets can either be mechanically fixed to the side of the lorry or bonded by means of a hot melt.

Use the 45' lap, FAP 808 laser, 2-4 watts 15 mm beam. This will inter facially weld the PP without the HAZ damage of US welding.