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Peel ply

wirejock

Well Known Member
Question
Can Peel Ply be used more than once?
It seems like it. I applied a section to a test piece to find out.
Just curious.
 
I can't imagine that it would be. It should be pretty much saturated with cured epoxy when you peel it off. If not saturated you have air gaps between the peel ply and epoxy that would defeat the purpose of peel ply. Also, while I did not find anyone around me, there are guys that build fabric planes that will most likely just give you their scraps.
 
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Jereme is right... If you've used it properly it should have absorbed the excess resin and leave you with a decent finish. Toss it.
 
Process

Interesting. I use the residual epoxy to make sure the peel ply is wet. Next day, peel it off. I would expect it to be stiff as a board but it's still pliable like it could be reused.
It was just a thought. I'm cheap.
 
Peel ply is dacron. You can buy it at JoAnn fabrics in large quantities cheaply. Try re-using it if you want to, but is it worth it? Cost is a few pennies to cut a new piece.
 
Jo Ann

Peel ply is dacron. You can buy it at JoAnn fabrics in large quantities cheaply. Try re-using it if you want to, but is it worth it? Cost is a few pennies to cut a new piece.

It was just an idea. Trash can is pretty full of the stuff.
I hadn't tried JoAnn. My Sweetie's favorite store. I'll check. Thx
 
Jereme is right... If you've used it properly it should have absorbed the excess resin and leave you with a decent finish. Toss it.

If the dacron absorbed the resin, it would be bonded to the surface. If you question that, put a piece of cotton on top of your wet resin. Or better yet, put a piece of fiberglass cloth on top of the resin. That will demonstrate what happens when the cloth absorbs the resin. The resin won't adhere to the dacron and hte weave is too tight for traditional epoxy to penetrate the weave (dacron strand is solid filament, not stranded like cloth or fiberglass), that is why it peels off after curing. The tackiness off the resin forces it to conform to the dacron resting against it. That is what gives the nice surface. If it absorbed into the cloth and somehow didn't stick, the surface would be very rough. Not sure if it is reusable or not, but expect that it is.

Larry
 
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My super cheap solution is "Bridal Satin" from Walmart. If I recall correctly, it's like $5 per yard. It's a 100% Polyester, slightly shiny on one side, satin material. Think wedding dress fabric. Once the Epoxy is cured, it peels off with light to medium-light force. Leaves a great finish for bonding more composites if needed. Best part is, apparently, it comes in fun colors... But I always buy white.

https://www.walmart.com/ip/Bridal-S...ing-Dress-Drapery-By-The-Yard-White/768534809

To answer the OP, MY "Peel Ply" is stiff and saturated with epoxy when I pull it off. No possible way to reuse it.
 
If the dacron absorbed the resin, it would be bonded to the surface. If you question that, put a piece of cotton on top of your wet resin. Or better yet, put a piece of fiberglass cloth on top of the resin. That will demonstrate what happens when the cloth absorbs the resin. The resin won't adhere to the dacron and hte weave is too tight for traditional epoxy to penetrate the weave (dacron strand is solid filament, not stranded like cloth or fiberglass), that is why it peels off after curing. The tackiness off the resin forces it to conform to the dacron resting against it. That is what gives the nice surface. If it absorbed into the cloth and somehow didn't stick, the surface would be very rough. Not sure if it is reusable or not, but expect that it is.

Larry

Larry, you seem to be describing a release layer, which can be a woven product or a film, rather than a peel ply.

The practical difference? After removal, a release layer leaves a surface unsuitable for bonding without further prep. If viewed under magnification, the surface, although perhaps mirroring the weave pattern of the release fabric, will be tend to be relatively smooth and shiny. The separation of release fabric or film and the workpiece was an adhesive failure.

A peel ply used to prepare a surface for subsequent bonds leaves a fractured surface. The separation was a cohesive failure.

In order to be a cohesive failure (a break within the epoxy matrix, rather than a separation at the material surfaces), the peel ply must remove cured epoxy from the surface...thus it must contain cured epoxy and cannot be reused.

My super cheap solution is "Bridal Satin" from Walmart. If I recall correctly, it's like $5 per yard. It's a 100% Polyester, slightly shiny on one side, satin material. Think wedding dress fabric. Once the Epoxy is cured, it peels off with light to medium-light force. Leaves a great finish for bonding more composites if needed. Best part is, apparently, it comes in fun colors... But I always buy white.

https://www.walmart.com/ip/Bridal-S...ing-Dress-Drapery-By-The-Yard-White/768534809

To answer the OP, MY "Peel Ply" is stiff and saturated with epoxy when I pull it off. No possible way to reuse it.

Two cautions...

Removal with light force can indicate it really is just peeling, not fracturing the epoxy.

A key issue in loss of bond strength is contamination of the bonded surfaces at some point in the process. Plenty of research papers on the subject. With a woven peel ply, one source of contamination is surface treatment and weaving lubricant. The WalMart fabric may be fine; I don't know anything about it. That said, using either aircraft polyester or standard composite industry products is a safe bet.
 
Larry, you seem to be describing a release layer, which can be a woven product or a film, rather than a peel ply.

The practical difference? After removal, a release layer leaves a surface unsuitable for bonding without further prep. If viewed under magnification, the surface, although perhaps mirroring the weave pattern of the release fabric, will be tend to be relatively smooth and shiny. The separation of release fabric or film and the workpiece was an adhesive failure.

A peel ply used to prepare a surface for subsequent bonds leaves a fractured surface. The separation was a cohesive failure.

In order to be a cohesive failure (a break within the epoxy matrix, rather than a separation at the material surfaces), the peel ply must remove cured epoxy from the surface...thus it must contain cured epoxy and cannot be reused.

Thanks for clarifying this. I have never used it and always assumed it was a release type application and it allowed re-application via conatining amine blush via separation from oxygen.

Larry
 
Interesting thread. I never heard of weaving lubricant but it makes sense. Guess I need to buy more Peel Ply.
To answer my own question, no. Peel ply is not reusable. Ibtried it on a sample. It saturates like the first use but leaves most of the epoxy behind when removed. At least, that's what it looked like.
 
Two cautions...

Removal with light force can indicate it really is just peeling, not fracturing the epoxy.

A key issue in loss of bond strength is contamination of the bonded surfaces at some point in the process. Plenty of research papers on the subject. With a woven peel ply, one source of contamination is surface treatment and weaving lubricant. The WalMart fabric may be fine; I don't know anything about it. That said, using either aircraft polyester or standard composite industry products is a safe bet.

Good to know, thank you! I never thought about it leaving contaminants for bonding the next layer.

The only work I've done with the Walmart Polyester is repairing cracks in my old RV-4 pre-honeycomb cowl. I usually just layer up 2-3 layers of Carbon Fiber (staggered edges between layers) and the Walmart "peel ply" works just fine for that. Never had any reason to try and bond a lot more structure to it after. If I do add layers, it's after I've already sanded on the section or part and I've never had any bonding or delamination issues (that I know of) because of the Walmart Polyester. I'm usually just using it to try and squeeze out excess resin.
 
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