Experiment Poly-U Glue vs Epoxy

[chrismp]

@bloefeld: elan also states that they use less energy now because their polyurethane system cures at room temp. seems like there's something we're missing, or it's just marketing bs.

[Bloefeld]

Now you're getting it! Experimenting is what we do. This is probably one of the few open source sites on the web where successes and failures are documented and shared. The variables are endless.

I think we have to come up with some standards like ASME only without the need for crazy expensive equipment.

One can learn a boat-load about a composite sandwich by doing a 4 point bend test. Essentially every load dynamic can be calculated by this single test.

Maybe I have to look into some better FEA software for my Alibre CAM!

Cheers,

Bloefeld

[skidesmond]

Update on the Poly-U glue experiment.... I made a pair of all wood skis the other day using Gorilla glue, no FG in the layup. The core was vertically laminated and then I used a layer of poplar veneer above and below the core. I also use a thin layer of cork on the base in between the edge tynes as a filler and to see if it would any effect as a dampening agent.

But, the reason for the update in the glue. yes it still bonded fine, HOWEVER, after pressing the ski for at least 12hrs, some of the glue still had not cured but I did not know that. The ski looked great when I took it out of the press. I left it on the work table and then came back to it a few hours later only to find the base had small bubbles every where. The bubbles were not there when I took the skis out of the press. The bases were dead flat.

I'm assuming some of the glue had not cured, then started curing on the work table, and Gorilla glue expands when it cures.

I put the skis back in the press for a few hours and it did help, most of the bubbles did press out, but a few did not. Not sure I can grind or file them down w/o going through the base. The skis will be ok for personal use but they were supposed to be raffled off for our race league.

So word of caution if you decide to try using Gorilla Glue. I'll look to see if there is a poly-u glue that doesn't expand. It bonds great for all wood layups even when using p-tex and VDS.

[Bloefeld]

Update on the Poly-U glue experiment.... I made a pair of all wood skis the other day using Gorilla glue, no FG in the layup. The core was vertically laminated and then I used a layer of poplar veneer above and below the core. I also use a thin layer of cork on the base in between the edge tynes as a filler and to see if it would any effect as a dampening agent.

But, the reason for the update in the glue. yes it still bonded fine, HOWEVER, after pressing the ski for at least 12hrs, some of the glue still had not cured but I did not know that. The ski looked great when I took it out of the press. I left it on the work table and then came back to it a few hours later only to find the base had small bubbles every where. The bubbles were not there when I took the skis out of the press. The bases were dead flat.

I'm assuming some of the glue had not cured, then started curing on the work table, and Gorilla glue expands when it cures.

I put the skis back in the press for a few hours and it did help, most of the bubbles did press out, but a few did not. Not sure I can grind or file them down w/o going through the base. The skis will be ok for personal use but they were supposed to be raffled off for our race league.

So word of caution if you decide to try using Gorilla Glue. I'll look to see if there is a poly-u glue that doesn't expand. It bonds great for all wood layups even when using p-tex and VDS.

Gorilla glue is moisture cured and a polyurethane. Polyurethane turns to foam in the presence of moisture. Gorilla glue could care less about the amount of heat and pressure you put on it. As soon as the pressure is released any uncured material will hunt out some moisture to cure and foam some more.

Heat has nothing to do with the cure process, Gorilla clue is a single component moisture cure adhesive meant for use with wood and other materials that absorb moisture. It does not have the mechanical properties to make a composite material suitable for use in skis.

Cheers,

Tony

[skidesmond]

Yup that's what happened, the glue found places to cure and it did. I did not use heat during the pressing and from what you said it wouldn't have made a difference.

Tony, I know you are an expert in adhesives, so help me understand why poly-U glue will or should not work (outside of the problem I had ) especially in an all wood layup of a ski? I have used it in other all wood layup skis with success and a FG layup. I realize that using it in FG layup is a real stretch but, it did bond fine and it's a ski I use racing w/ very good results. Is it a matter of time before the bond starts fail and delams?

The glue says it will bond to wood, metal, plastic, etc. I know some use it to glue UHMWPE to wood cores with success.

I've used this glue when making ski cores and in more typical applications (furniture, etc). Granted the furniture just sits there, where a ski is dynamic and constantly bending and flexing.

Thanks

[Bloefeld]

Yup that's what happened, the glue found places to cure and it did. I did not use heat during the pressing and from what you said it wouldn't have made a difference.

Tony, I know you are an expert in adhesives, so help me understand why poly-U glue will or should not work (outside of the problem I had ) especially in an all wood layup of a ski? I have used it in other all wood layup skis with success and a FG layup. I realize that using it in FG layup is a real stretch but, it did bond fine and it's a ski I use racing w/ very good results. Is it a matter of time before the bond starts fail and delams?

The glue says it will bond to wood, metal, plastic, etc. I know some use it to glue UHMWPE to wood cores with success.

I've used this glue when making ski cores and in more typical applications (furniture, etc). Granted the furniture just sits there, where a ski is dynamic and constantly bending and flexing.

Thanks

If you look on page 2 you will see notes with my polyurethane expert on the topic of using polyurethane for application in skis by non-volume users.

Adhesives are not the same as composite resin systems. They can be similar but do not serve the same purpose.

In the case of Gorilla Glue it does not have the bulk properties to make a composite. No matter what you do, it will not help you create a good fiberglass matrix of enough strength to be useful.

It is great for bonding your core but there is no structural adhesive of any sort for less than $300 per gallon that will bond with UHMW. Some PU adhesives are gooey enough to sort of stick to the surface but will never cure and create a true bond. The reason is that UHMW has a very low surface energy and the adhesive has to have a surface energy of at least 10 dynes less than the plastic to bond.

I am surprised that you ever got Gorilla Glue to work in a FG layup and got decent performance from it. It has way less than half the bulk properties I would even consider for use in composite construction. I expect that the fiberglass had enough moisture content for the glue to cure. It does have excellent adhesive properties so with the combination of enough moisture and the press pressure I think you got lucky and it worked.

I like urethane resin systems a great deal, but I have only used them in making pultruded products where the cure process is subject to a great deal of control and the moisture is dealt with by preheating everything in the part.

I think there may be some polyurethane/epoxy hybrid products that my be useful, but the ski epoxies that are commonly used by people on this site are in my opinion excellent and I can see no reason not to simply use them.


Cheers,

Tony

[vinman]

As for bonding of UHMWPE with PU glue. It is only being used to provide enough of a bond to attach the sidewall to the wood core long enough to get the core profiled and into the laminate. To achieve even this bond, it needs to be abraded and flamed to get the PU glue to stick. Once the profiled core is in the layup the PU glues does little to nothing as far as structural integrity goes. As you point out the real strength comes from the epoxy and fiberglass matrix.

If I could figure out a way to heat cure the epoxy and not have the clamps in the way I'd use my regular epoxy to do sidewalls. But at a room temp cure with my epoxy it would not be feasible to do this.

[Bloefeld]

As for bonding of UHMWPE with PU glue. It is only being used to provide enough of a bond to attach the sidewall to the wood core long enough to get the core profiled and into the laminate. To achieve even this bond, it needs to be abraded and flamed to get the PU glue to stick. Once the profiled core is in the layup the PU glues does little to nothing as far as structural integrity goes. As you point out the real strength comes from the epoxy and fiberglass matrix.

If I could figure out a way to heat cure the epoxy and not have the clamps in the way I'd use my regular epoxy to do sidewalls. But at a room temp cure with my epoxy it would not be feasible to do this.

This is a very complicated topic as it refers to surface science and the necessary and sufficient conditions of all adhesion. It is at the core of adhesion science.

To my knowledge their are 3 common methods and 2 not as well known methods to allow UHMW to meet the requirements for adhesion.

Crown plastics apparently abrades and flame treating.

Honeywell uses plasma to treat Spectra as does Dyneema.

The other common method is to corona treat the plastics.

In all cases the surface energy of the plastic is lowered and polar bonding species are temporarily put onto the surface of the plastics. In each case, over a period of time this effect is lost. Don't buy too much base material and not use it.

The other two techniques are sulphination and fluoro-treatment. Both are permanent but require sophisticated process equipment and control to perform. I have samples of fluoro-treated UHMW that are nearly a decade old and are still excellent for adhesion.

The problem you face is that flame treatment is very difficult to do properly and well. Bad treatment results in very inconsistent adhesion.

If there was enough demand for sidewalls, I could arrange to have some UHMW PE fluoro-treated.

Cheers,

Tony

[vinman]

Flaming is not hat hard to do, but yes to do it right can be tricky, ask most any of the builders here who do it, but it can be done successfully, ask most any of the builders here who do it.

Abrade with 60 grit belt sander, flame with a propane torch using the hottest part of the flame but carefully not to scorch the material, Do it less than 30 min before layup, and redo and previously factory treated plastics as well, for the reason you state. Test with a water drop test to make sure the surface tension has been lowered.

Abrading gives you mechanical bonding by making th surfaces hairy, the flaming gives you an oxidation layer for chemical bonding.

Complex science is not always complex in practice.

[Bloefeld]

Flaming is not hat hard to do, but yes to do it right can be tricky, ask most any of the builders here who do it, but it can be done successfully, ask most any of the builders here who do it.

Abrade with 60 grit belt sander, flame with a propane torch using the hottest part of the flame but carefully not to scorch the material, Do it less than 30 min before layup, and redo and previously factory treated plastics as well, for the reason you state. Test with a water drop test to make sure the surface tension has been lowered.

Abrading gives you mechanical bonding by making th surfaces hairy, the flaming gives you an oxidation layer for chemical bonding.

Complex science is not always complex in practice.

The water test is a good approximation for surface energy, use distilled water for best results, but don't always assume that because a plastic passes the water test that it has low enough surface energy to bond to any and every adhesive.

Abrading only gives more surface area for the flame treatment to react with, it does nothing in this case to improve adhesion, only the carboxyl's created by the flame treatment give you anything to bond to. The slight intertwingling of the abraded surface will only give superficial adhesion.

You are correct, it can be done and done well with practice.

The bond is not great but probably good enough. In fluoro-treated UHMW PE the plastic always failed before the bond in ASTME tests for adhesion.

I feel certain that you would agree the UHMW makes much better sidewalls than ABS.

Cheers,

Tony

[vinman]

Good tip on the distilled water.

Good point about the increased surfaces area for the flaming, I still feel like the abrasion does improve the mechanical bonding to some extent.

A good article on gluing plastics and the resource for my statement on flaming within 30 min of layup.


http://www.epoxyworks.com/26/pdf/Gluing ... _Gflex.pdf

Although this article indicates an alcohol wipe before flaming improves bonding. What's your though on that?

Des sorry for the hijack.... I may repost some of this in the uhmwpe bonding thread if it seems worthy.

[skidesmond]

Good tip on the distilled water.

Good point about the increased surfaces area for the flaming, I still feel like the abrasion does improve the mechanical bonding to some extent.

A good article on gluing plastics and the resource for my statement on flaming within 30 min of layup.


http://www.epoxyworks.com/26/pdf/Gluing ... _Gflex.pdf

Although this article indicates an alcohol wipe before flaming improves bonding. What's your though on that?

Des sorry for the hijack.... I may repost some of this in the uhmwpe bonding thread if it seems worthy.

No worries. It's all good info.

The point of the experiment was to find another adhesive/glue/bonding agent that was relatively in-expensive, easy to get, easy to apply and bond to the materials we use in skis/boards.

The bubbling was a real disappointment. Even though I had success of sorts w/ poly-u glue, I think it's over.

[Richuk]

Vinman, G-flex is expensive. An alternative approach is to flame treat the plastic - 6 inch width and lay it up over a similar sized thin piece of wood, say 5 mm think. Put in the oven at the usual heat and pressure, remove, cut and bond wood to wood. I'm not the author of this method, but I can say it works.

[vinman]

I'm not using gflex, I just thought it was a useful article about bonding UHMWPE, specifically the flaming method they describe.

That is an interesting idea, bond the Ptex to the wood prior to ripping it into sidewall strips.....hmmm might have to think about that.

[Bloefeld]

Good tip on the distilled water.

Good point about the increased surfaces area for the flaming, I still feel like the abrasion does improve the mechanical bonding to some extent.

A good article on gluing plastics and the resource for my statement on flaming within 30 min of layup.


http://www.epoxyworks.com/26/pdf/Gluing ... _Gflex.pdf

Although this article indicates an alcohol wipe before flaming improves bonding. What's your though on that?

Des sorry for the hijack.... I may repost some of this in the uhmwpe bonding thread if it seems worthy.

Upon reflection I think that abrading the plastic and then flaming will just give you little chunks of carbon that will break off from the plastic and decrease adhesion. So the alcohol wipe makes sense and clearly gives better bonding.

I am fortunate in that I can get a couple of strips of UHMW treated with fluorine at anytime at no cost, so I get 6,000 or so psi of shear adhesion (the failure of the UHMW)

There is a great book out there called "Adhesion and Adhesives Technology, An Introduction 2nd Edition" by Alphonsus Pocius, published by Hanser. Al gives a great description of all of the mechanics of bonding and gives a good explanation of all of this stuff. No doubt there are library copies all over the place. It is worth the read to give a good grounding in adhesion science.

Cheers,

Tony