on bonding ptex sidewalls, and delams

[knightsofnii]

so, first off:
how many of you have really had repeated success with getting a strong bond with uhmw sidewalls?

this last one delamed on the bottom half only, right in my kitchen, never been ridden, like when justin timberlake met brittney.

I dont understand why only bottom half is delamed. Could it be happening due to cutting away the flash? Could the heat from a jigsaw blade cause this?

I sanded these things for a good hour. Cleaned with MEK, flame treated, cleaned with MEK, used the primer supplied to me by QCM, made sure every square mm of surface was completely saturated with resin, heated the press properly, got correct even pressure.

It was a bit of work to cut the flash off these ones. On the last few the cores were a pinch narower so the sidewalls didn't really stick out, they were near exact width, this board they stuck out so i had a fun time trying to cut them. Topsheet side is routered back, i dont know or recall if there was any delam gaps between top of sidewall and top glass layer prior to routering. Like i said all the delams are between bottom of sidewall and bottom glass. I would chalk it up as shitty flaming or sanding or cleaning and prep work but then i'd expect it to be on both sides.

Either way, I'm really disgusted with the results we've had with ptex sidewalls, and its time to move on to something better. Ive tried everything aside from running a bead of JB-Weld along the sidewall areas.
That's it i'll make flooded casted sidewalls out of jbweld , wait a second...

[G-man]

Hey Doug,

Flame treating the surface of UHMW is much more of a science than most people think. Many variables can significantly effect the dyne level of the treatment... humidity, temperature, gas/oxygen ratio, etc. The only way to achieve constant bonding results is to have a consistent process that is measurable in every respect. The surface treatment machines that are used in industry have elaborate feed-back systems that constantly adjust the gas/oxygen ratios in order to compensate for other environmental changes. The speed of the material past the flame, and the distance of the flame from the material is set by trial and error dyne level testing on material that hasn't been abraided (abraision alters how the dyne solutions react at the material surface). Once a particular set of surface treatment parameters produces the desired dyne level, every process parameter is locked in, and the abraided material is processed in exactly the same manner. Quality control is maintained by periodically processing non-abraided material and measuring surface tension via dyne testing.

A properly done surface treatment is only a few molecules thick. I've read some posts on this site where the builder flame treats, then sands the material surface. This completely removes any surface treatment that may have resulted from flame treating. I've also seen many posts where a builder states that a proper flame treatment results from slightly melting the surface of the UHMW, also not correct.

I know it may seem difficult to understand why the base-side surface of your side wall delaminated and the top surface didn't, but if your process was very similar on both surfaces, the bad news is that the top surface probably isn't bonded that well either. Maybe you went just a bit faster or slower with the torch, or the flame was adjusted just a little differently after you turned the core over an re-lit the torch, or maybe you had the flame just a bit closer or farther away. It doesn't take much of a difference to make a difference.

If you do a search of some of my older posts regarding flame treatment, you'll find a bunch more information from the research and testing I've done. This is just my opinion, but unless you're willing to spend the sorta big bucks to invest in a good flame treatment system, you're wasting your time trying to get consistent results with UHMW. Without the proper equipment, you might get lucky once in a while and things will stay together, but then the next board will fall apart. You certainly can't consider selling boards that aren't consistently well bonded... and you can't get consistent flame treating results without the science of surface treatment.

Not what you wanted to hear, I'm sure... and others will certainly have differing opinions. Good luck on getting things worked out.

G-man

Edit: just re-read your post and see now that you've already decided to move away from using UHMW. Good plan. I'll leave the stuff I wrote because I'm sure that others are experiencing the same frustrations that you have.

[knightsofnii]

G-Man, nope, definitely was expecting something along these lines from you.
We are so fortunate to have someone like you here who has gone to painstaking lengths to research and test out this stuff.

One thing though, do you think it was possible that the jigsaw blade did it like I was thinking? Like maybe overheating dded (fucked) up the surface treatment?

And yes I have also read other places that flame and/or corona treatment only treates ONE molecule deep.

I sanded the living shit out of these things, got them nice and furry, flashed them with the blue part of a low flame, just so you could see a shadow where the surface was expanding, no melting going on except for the occasional hairy piece that was hangin off. Anyway, i'm done. What sucks, is that I have like 10 already built cores WITH ptex sidewalls attached. I was having issues with these cores already, and this non bonding shit is just the icing on the cake. This board came out perfect in every other way. I was ready to hand it off to a team rider.

All jokes aside, after typing that post last nite, i pondered for a good hour about how I could make a sidewall with JB-Weld, hahaha. Gonna do some experimenting.

We're officially down until we come up with a better sidewall

[G-man]

Doug,

Yes, I too have a few pretty cores leaning in the corner that have UHMW side walls already attached. I haven't had the heart to toss them in the trash, but I also know that I'll never lay em' up because I can't be sure that they'll stay together. Of all the skis that I built with UHMW sidewalls, half of them came apart to some degree on the first time out. The other half have a few dozen days on each of em', and they're still going strong. I did as close the the same flame treatment as I could on all of them.

I talked with a company that supplies flame treating systems to larger ski and snowboard manufacturers, and they indicated that a smaller system could be had for about $20,000. If the surface treatment is done correctly, UHMW bonds super well. Crown obviously has it down really well as seen by how well their base material bonds to the bottom composite layer. I always thought it would be really enlightening to visit the Crown factory and take a tour to see how they do their surface treatment and quality control. I would be great if somebody who lived close to the Crown factory could take a tour and post a video.

Yes, I think that the physical action of a band saw or jigsaw can be pretty hard on the epoxy/UHMW bond. If you use a jigsaw, and do your trimming with the base facing up, using a down-cutting blade would likely cause less stress on the base layer bonds, would, in turn, tend cause more stress on the top layer bonds.

As I see it, we builders have about 4 basic options in dealing with the side wall issue... (1) a good flame treating system and sticking with UHMW or ABS, (2) cap construction, (3) wood sidewalls, or (4) coming up with some other material that is tough, flexible in the cold, and bonds well without surface treatment.

G-man

[brewster]

If the board is trashed, have you tried to pull the top sheet,etc off of the top of the sidewall? Any difference? Does this happen on all of your boards?

[knightsofnii]

the board looks too damn good to even think of doing that

the flash can be examined though. so far every board I built, i took the flash and tried to pull the sidewall away from the other laminates, it pulls apart like the only thing holding it together was compression itself. Someone with rheumatoid arthritis could peel the ptex away from the glass.
And on one side that i cut off this board i did this, and peeled it away with ease, though at the time i chalked it up to the board needing to sit around for a bit for full cure, that was last friday nite so its been a week now.

i'm seriously gonna make a mockup of a profiled core and cast some JB-Weld onto it. I'm very skeptical about it but at this point I'm willing to try anything.

G-Man, does ABS also have to be flame treated? or does it need some other treatment that is just as troublesome?

I know Crown will profile sidewalls for you, and then deliver them sanded and flamed. But its pricey, it apparently takes the first 3 "boards" of material put through the machine just to get it calibrated to do the profile, etc.

[SHIF]

I've built several pairs using black reprocessed UHMW for sidewalls. Most of these skis exhibit minor delams between the sidewalls and the base glass layers in the area aft of the bindings. These cracks don't seem to effect their performance, especially in the deep powder which is what they were built for in the first place. I've had good results repairing the larger of these cracks by wicking-in super glue and clamping them tight.

Good reading here: http://www.reltekllc.com/adhesives-for-uhmw.htm

Primer material designed for bonding UHMW and similar plastics that looks ideal: http://www.reltekllc.com/bondit-a43.html

Unfortunately this stuff is prohibitively expensive, ~$1K/quart. A 5ml syringe costs over a hundred bucks! I've got their price sheet if you're interested.

Furthermore I believe that UHMW sidewalls add too much dead weight to the ski. My next pair will have Massaranduba (an Amazon rain-forest hardwood) for the sidewalls. This wood is as dense as UHMW but will bond very well with epoxy. Plus it will become a structural element in the ski, not just a protective bumper. It is commonly used as decking, it does not absorb water.

I will still incorporate 2mm thick P-tex tip and tail filler material. This stuff bonds really well and adds so much durability to the skis.

-S

[knightsofnii]

yea the tipfiller bonds real well cuz its factory treated on a gazillion dollar machine like G-man mentioned , and you're right, as long as you keep it cleaned liberally and dont do any sanding or too much scraping along the edges, etc, basically dont alter its surface, and it bonds just great .

another thing i might try is the cap-to-sidewall method, but that would probably involve eliminating my cat track to get a good cap, and then avoiding a lumpy base will be pretty much a headache.

i've got another idea which would involve using extra edge material, and some tip fill, and making a Blak Sheep exclusive sidewall, but that's gonna take lots of time and crap, and I think it would involve altering the surface of the tip fill just when I told you not to do that very thing . We'll see.

Who wants to brainstorm this more? We've got woods like bamboo, Jb-weld is gonna be a bitch to machine and/or get to flex right but i'm tryin it anyway, what about CAULK??? Foam is right out, too porus. first thing that comes to mind just throw it out there and we'll figure out the pro's cons etc. i gotta go finish this board so we can destroy it on the slopes tomorrow

[pentagram]

I had a sidewall idea in my head for some time.
Gives the look of a ptex side wall with out all the bonding issues?maybe.
Anyway the idea is to get a nice strong wood..anything that has had success as an all wood side wall, router or whatever your sidewall angle..lets say 45 degrees, than get ptex base matrerial and epoxy and clamp it to the side of the wood, two sidewalls at 45 degree would be easy to clamp together. I would personally back the base material with some light kevlar or similar.
You get a sidewall which has less weight, abrasion resistant, strong and the base material comes ready for a good bond.
The only thing you then have to worry about is the 1.2 mm basematerial bond to the laminates.
Has someone posted this idea or tried it before?..
Thanks Doug for always getting good post strings going.
Cheers
Lance

[doughboyshredder]

my boards have all had p tex sidewalls flame treated during layup after rough sanding and have zero signs of delamination after getting consistently abused.

I completely disagree with the concept that you can't properly flame treat without a machine, etc...

The factory I worked in flame treated sidewalls by hand, and I know others do as well. Somebody posted a tap plastics video on here about how to tell if your plastic is treated properly.

I do think that if your jig saw blade is leaving any sort of scarring on the edge that it may be grabbing and ripping at the sidewall material also.

pourable urethane is one that I want to try. http://www.eagerplastics.com/ure.htm

pmc790 is a 90 durometer urethane which could be applied to the core along with a primer. Or possibly applied after pressing, by routing out a void to be filled with the urethane.

[G-man]

Hey Doug,

Some information sources say that ABS needs to be flame treated and some say that it just needs to be chemical treated. Here's a link to a page that says it just needs to be abraded and chemically treated (down the page about half way):

http://209.85.173.132/search?q=cache:Zs ... =firefox-a

G-man

[G-man]

I completely disagree with the concept that you can't properly flame treat without a machine, etc...

I'm not saying it can't be done, just that it's difficult to get consistency when doing it by hand. I'm sure that some folks have a better sense for how to do it by hand than others do. Epoxy has a surface tension of 47. In order to get a good bond with the substrate polyethylene, the surface tension of the substrate needs to be increased at least 10 dyne above the surface tension of the bonding agent. The surface tension of UHMW in it's normal state is 31. So, that means that the surface energy of the UHMW needs to be increased at least 26 dyne (to 57) in order to achieve a good bond. I always shot for at least 60 dyne, and I got into the mid-60's a couple of times.

Here's the flame treating video link for Tap Plastics:

http://www.tapplastics.com/info/video_d ... =quicktime&

One of the big misconceptions in bonding abraded UHMW is that if water 'sheets out' on the material, the material is ready for bonding. On smooth material, it is true that if water sheets out, the material has at least a surface energy of 72 dynes (the surface tension of water at room temperature). Abrading UHMW changes how water sheets out on the UHMW surface. Here's a good test... grab a scrap of base material and put a few drops of water on the non-treated side. See how the water contracts into itself on a hydrophobic response? Now, dry off the water and abrade the same area with piece of sandpaper, and then put a few drops of water on the abraded area. Now the water sheets out really well, which by some recommendations would indicate that it's ready to bond well with epoxy, but we all know that such is not the case, and that if we tried to layup a ski with UHMW that was only sanded, the ski would fall apart before it even got out of the press. So, my point is, you can't rely on the water test on abraded material.

Here's a pretty good link to more bonding stuff:

http://www.omnexus4adhesives.com/servic ... aspx?id=20

One thing to keep in mind when testing other polymers as sidewall possibilities is to be sure to do a test on a sample after it has been in the freezer for a bit of time. Many polymers seem like they should work well as sidewall materials... tough and flexible... but they shatter like glass when flexed at temps down around freezing.

G-man

[brewster]

It may be possible you are over sanding your sidewalls. I remember reading a paper sometime ago about bonding UHMW and seeing a graph with a Gaussian type distribution for abrading vs bond strength. I also wonder how too much abrading will effect surface energies. I will try to track down the ref.

Edit: Gaussian = "bell curve" In other words, too much or too little = crappy adhesion.

[knightsofnii]

doughboy,
Could you please make a video of how you flame treat sidewalls?
That video has not convinced me of anything, and the sound didn't work .

I'm gonna peel the sidewalls out of a junk board, and fill them with somethin special, to see how it comes out .

[Head Monkey]

Like doughboy I’ve also had no problem bonding my ptex sidewalls. The material I have is from Crown. I abrade with 80 grit alu-oxide sandpaper just until the surface is no longer smooth, then flame treat with the very tip of a flame from a propane torch. I’ve got boards with 50+ days of abuse (and I mean abuse) on them so far with no problems.

The only suggestions I have for you are the following:

1. Are you quite sure you’ve mixed your epoxy correctly? I.e., you’re not mixing by volume when you should be mixing by weight are you?
2. Watch the heat you generate on your edges when cutting flash, cleaning up the edges, etc. If you can’t hold your bare hand on the edge because of the heat, then it’s too hot. Cool with water if you have to.
3. I don’t actually clean my sidewalls after flame treating with anything… I keep everything pretty clean to begin with. I’ve never used MEK or acetone on any of my parts. I do use alcohol on some of the parts, though not the sidewalls. Is it possible that one of these is actually not being as helpful to you as you think? I.e., does the second MEK cleaning you mention above accidentally destroy the fragile surface treatment, either due to the MEK or any scrubbing you might do?
4. Is it possible that in sanding your sidewalls you inadvertently made them a bit too thin? This would result in reduced pressure on your sidewalls during pressing (the track would be supported by the core only) and could yield a brittle bond along the sidewalls.

Overall, I’d say you should try some targeted experiments with your sidewall materials and your processes to see if you can find where you’re going wrong. Not in a whole board… just small sample preparations and layups until you find the problem. For all the builders who I know that are clearly doing the same thing without expensive equipment or flame treating processes, I’ve got to believe you can make this work.