I' m currently making tensile test samples for Unidirectional (UD) Prepreg. Therefore, I need to fabricate a 1mm thick unidirectional sheet. I used two glass plates that sandwich five layers of UD Prepreg and are vacuum baged and cured in the Prepreg oven at 100°C (see attached pic). The two glass plates were treated with six layers of Easylease coated with a 20min. separation between each coating. However, I still have the problem that the Prepreg sticks to the glass. I cannot manage to take the Prepreg sheet off the glass without braking the glass or the prepreg sheet (see attached pic). I tired this several times already. Any Idea how to resolve this? What about trying to use PVA or wax as a release agent, instead of Easylease?

Looking forward fot some help

Kind regards

Pier

How are you applying the Easylease? Describe your process when you apply it, ie. Do you soak a cloth and wipe it on? Do you wipe it off at all after applying it, or are you buffing the surface at all after application? Are you cleaning the glass well prior to application? 

How old is the Easylease, and more importantly - how has it been stored? It's very unlikely that it has expired unless it hasn't been stored very well. But it's possible.


Wax and PVA won't work for pre-preg, at least not the typical stuff. You can get high temperature release wax, but I haven't used any personally. Really there shouldn't be any need, the Easylease should be the better product and it should be working - better to work out what is going wrong. 

Thanks for answering Hanaldo,

I'm using the lint free solvent application wipes from easycomposites. I hold the wipes onto the easylease container opening and tip it up and down for three times on tree different locations (three times a round surface area) on the wipe. I then buff the easylease onto the glass plate surface making sure to do that with the soaked area only. I can then see that the easeylease is smeared onto the glass so there is a visual confirmation that the product is being applied. Then I wait 20min and I repeat the same process another 5 times at 20min intervals. I would wet the same surface area spot on the wipes and use the same to buff again. This is it, can't be simpler then that one would think...
The easylease that I use worked in other occasions. 50% probability, one release from each new glass plate with the same procedure. The second release was usually not successful any more. I got glass braking off the glass plate and sticking to the composite. Any other suggestions...

Yeh it sounds like you're going about it the right way. The one thing I might point out is that you may be going a little heavy handed with it, which is a common cause of failure. Over-application is actually detrimental, as if the film you are applying is so wet that it can form a droplet and bead up then it will do that rather than cling to the mould surface - something that is especially true for glass surfaces because glass already has quite a low surface energy. You want to be applying just enough to leave a film on the surface, but not so much that it forms streaks behind the cloth... What I do is I actually cut the solvent application wipes into 8 strips, and then use them individually. This way they can absorb less material, so it isn't as easy to over do the application. For such a small surface, I would also suggest only applying the Easylease to one area of the cloth rather than the three that you have been doing. Give it another try using this method and see if it works better. 

Another reason for doing the 8 strips is you shouldn't reuse the same piece of cloth for each application of release agent, you should throw each piece away and use a new piece for the next layer. What happens is the release agent that remains on the cloth partially cures, and then when you apply more to it, the solvents partially dissolve it and transfer to your tool surface as a greasy film. In practise, this shouldn't really cause any problems other than a bit of a streaky surface that will transfer to your finished part - but it is something to avoid regardless.


You can also do a quick 'tape test' prior to applying any resins which should indicate whether the release agent is working. If you place a piece of masking tape on the glass before you apply any release agent and peel it off, you should feel a fair bit of resistance. Then apply your release agent, and before you apply any pre-pregs or resins, place another piece of masking tape on the surface. If the release agent is working, you should find the masking tape will come away with very little effort, and in fact it may not stick to the surface at all and simply curl up. If it doesn't feel much different to before you applied the release agent then it's a pretty safe bet that the release is going to fail. 

+x

 

Hanaldo - 1/2/2018 2:36:31 AM

Yeh it sounds like you're going about it the right way. The one thing I might point out is that you may be going a little heavy handed with it, which is a common cause of failure. Over-application is actually detrimental, as if the film you are applying is so wet that it can form a droplet and bead up then it will do that rather than cling to the mould surface - something that is especially true for glass surfaces because glass already has quite a low surface energy. You want to be applying just enough to leave a film on the surface, but not so much that it forms streaks behind the cloth... What I do is I actually cut the solvent application wipes into 8 strips, and then use them individually. This way they can absorb less material, so it isn't as easy to over do the application. For such a small surface, I would also suggest only applying the Easylease to one area of the cloth rather than the three that you have been doing. Give it another try using this method and see if it works better. 

Another reason for doing the 8 strips is you shouldn't reuse the same piece of cloth for each application of release agent, you should throw each piece away and use a new piece for the next layer. What happens is the release agent that remains on the cloth partially cures, and then when you apply more to it, the solvents partially dissolve it and transfer to your tool surface as a greasy film. In practise, this shouldn't really cause any problems other than a bit of a streaky surface that will transfer to your finished part - but it is something to avoid regardless.


You can also do a quick 'tape test' prior to applying any resins which should indicate whether the release agent is working. If you place a piece of masking tape on the glass before you apply any release agent and peel it off, you should feel a fair bit of resistance. Then apply your release agent, and before you apply any pre-pregs or resins, place another piece of masking tape on the surface. If the release agent is working, you should find the masking tape will come away with very little effort, and in fact it may not stick to the surface at all and simply curl up. If it doesn't feel much different to before you applied the release agent then it's a pretty safe bet that the release is going to fail. 

I will try to use eight separate strips and try the process again...
I can confirm that I had streaks left behind on the glass when applying easylease and that I reused a lint free cloth that was used and soaked before.
I also want to point to out, that the easylease layer was visible before vacuum bagging and that it disappeared compleately after processing the prepreg layup in the oven. It is, as if the glass would have soaked it up, the film evaporated or diffused into the glass? Thank you for helping out once more.

Yeh the residue would have transferred to the pre-preg.

I think this will be the issue. It's a bit of a strange one, as it doesn't always cause problems. It's a bit like rushing the application and just doing 5 coats one after another. Sometimes it works fine, sometimes you will get sticks. It's quite amazing that a product that works so well can be so finicky to apply, but you have to remember that it is actually a resin. 

When you try it again, if you accidentally over apply it and notice it streaking again, don't worry too much - just wait a few seconds and then gently wipe over it again with a clean lint-free cloth to spread the film out. 

!

Glass is sometimes a tricky surface to get a good release.
I always use
https://shop.hp-textiles.com/shop/Formtrennmittel/Formtrennmittel-95/Hochglanz-Trennmittel-HP-HGR5.html
Never had any issues with it, regardless of the surface.
I use a hand spray bottle (like glass cleaner) to apply it to the mold, then wipe it in with a micro fibre cloth, and use a new one every day. When I got enough old ones, I put them in the washing machine.
What I like about this release agent, is that is water based, and therefore  can be washed of easily if there is the need to. So no build up issues. I usually only do one application,  even on new molds.

+x

 

oekmont - 1/3/2018 10:29:58 AM

Glass is sometimes a tricky surface to get a good release.
I always use
https://shop.hp-textiles.com/shop/Formtrennmittel/Formtrennmittel-95/Hochglanz-Trennmittel-HP-HGR5.html
Never had any issues with it, regardless of the surface.
I use a hand spray bottle (like glass cleaner) to apply it to the mold, then wipe it in with a micro fibre cloth, and use a new one every day. When I got enough old ones, I put them in the washing machine.
What I like about this release agent, is that is water based, and therefore  can be washed of easily if there is the need to. So no build up issues. I usually only do one application,  even on new molds.

Oekmont, thank you for your comment. I will definitely try this release agent and test it. I just ordered one sample. I will post my results as soon as I get the product...

But usually easylease should work very well. Have you cleaned the glass before applying the release agent? Maybe there is something on the glass, wich causes this issue.