Shed Technology: XPS & Other Tests

General Discussion
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Well I finished laminating the test panel just before noon.  Used an old 30" x 48" piece of 6-oz e-glass thas been lying around in a drawer for years. Laminated with some old RR Kwik Kick I need to use up.  I still have enough of both for several more tests.

I am skeptical about the sealer.  I am not sure whether two coats of sealer and sanding all sealed surfaces with 150 grit was the right move.  But I will know when I pull the glass tomorrow pm or Monday and see how much foam comes up in each quadrant.

I got a carpet seam roller and have a Woodpecker covering/perforation (roller) tool on the way.  The Woodpecker tool is an interesting tool I stumbled across while searching the internet.  It may have potential.  I have many more combinations of variables to look at now.

I discoverd the propenenitrile ethenyl benzene in the new DOW blue mix is also called styrene-acrylonitrile (SAN).  The surface energy value I finally found for SAN is 40 dyne/cm.  Much closer to epoxy’s 45 than styrene’s 33.  Depending on the amount of SAN in the mix, the new DOW blue should bond better with epoxy than polystyrene does.

I ran a concurrent test with my updated “low budget” resin warmer this morning too – worked great.  I will post pictures and a description in this thread also.

@ Barry, I think I may have a better solution for the area constantly under foot/high concentrated impacts.

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I got my Woodpecker tool in the mail today.  I played with it on a piece of scrap XPS.  I rate it as having very high potential for improving epoxy bonding with XPS.  Paid $10.00 + $3.50 shipping on Etsy, a bargain – like new.  Stoked.

I peeled the glass from the XPS last night.  I needed good natural lighting for decent pictures.  Hopefully the right lighting today**…**

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Portable, adjustable glassing stand (aka ironing board)

All quadrants simultaneously laminated with the same batch of epoxy resin

 

Peels from XPS surfaces sanded with 40-150 grit and sealed before glassing with Secret Sauce (aka polycrylic concrete sealer):

150-grit surface

 

100-grit surface

 

60-grit surface

 

40-grit surface

 

Another view of XPS surfaces sanded with 40-150 grit then sealed before glassing:

150-grit surface

100-grit surface

 

60-grit surface

 

40-grit surface

 

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So from what I see, the rougher the better adhesion correct?

Be interesting when you use the roller tool you purchased.

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No surprises there.  I’d be interested in seeing a side-by-side comparison with and without the ‘secret sauce.’

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I have never seen peel from EPS. Curious if anyone has and can give a brief description/comparison.

I have, many years ago, stripped glass from poly resin board and it pulled little chunks of foam even when I really tried not to. If I just pulled it got ugly fast.

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In sandwich, skin don’t delam because of forces that tear off but because of shear caused by buckling instability of thin compressed skin. If you want a valid test you must do a 4 point bending test.

Epoxy eps bond shear strengh is stronger than shear strengh of foam so when skin buckle foam tearing that’s why you have a layer of foam bead gluded on skin.

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I love Sways for exactly what I am reading here. 

All the best, boys

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@ Lemat – I do not have the time or equipment/money for 4-point bending tests.  I believe that low density/low min. compressive strength XPS foam tests should give me some usable information about adhesion between epoxy and XPS.

@ Dr. Strange – I peeled several PU/PE longboards in the past.  I was surprised how little foam was pulled up.  I still had plenty of good foam to work with.  Funny you should mention EPS, I have been planning to play with Secret Sauce on it too – different reasons.

@ Barry Snyder -- No surprises.  The greater irregular bonding surface created with coarse sandpaper caused more foam to pull up than with higher grit surfaces -- better anchoring.  Yeah, I really want to try the perforation rollers next.
@ John Mellor -- Agreed.  Sealed vs. unsealed was/is the central objective of the tests. The initial hypothesis was/is sealer will improve epoxy adhesion with XPS.  The null hypothesis is sealer will not improve epoxy adhesion with XPS.
For the first test, I was more interested in seeing whether the polycrylic sealer would bond with XPS and whether epoxy would bond well enough with the sealer.  The results suggest epoxy adhesion with sealer is stronger than sealer adhesion with XPS.  Side-by-side sealed vs. unsealed is definitely needed.  I decided that looking at different grit effects in this preliminary bonding trial could also get me some surface roughness information at the same time.
_____
Observations
*  The 1.5 pcf/15 psi XPS insulating foam clearly tears and crushes very easily.  I can see how adding a wood veneer (Lavarat) or cork skin (melikefish) to the foam surface would minimize surface damage by dissipating/dispersing point impacts over a broader area.
*  Notice the greater amount of foam on the (numbered) edge opposite the side used to peel up the glass patch.  The peel edge was taped to avoid this effect.  The opposing/numbered edge without tape -- with resin drip over the foam edge -- appeared to have much greater mechanical bonding/leverage (bottle-opener effect?).
*  Uniformity -- while coarser grit appears to improve adhesion, it lacks uniform distribution over the entire surface.  The deeper grit cuts pulled up the most foam.  But the deeper cuts are random with gaps between them (areas of lower bonding?).
I believe perforation rollers could create more uniform mechanical bonding over the entire foam surface to be glassed.
I think I will look at the effects of perforation next.  Sealed vs. unsealed?  What final sanding grit before perforation?  Too coarse, and the deep sanding grooves will likely impact the effects of perforation -- especially uniform distribution effects.
Adding perforation rollers for testing too has significantly increased the number of potential variable combinations**...**
 
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Lemat…Exactly spot on.

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Ive used two types of Dow XPS in the past…white and blue…as far as I was told by Dow , the only difference is the colour. There is another one = Dow pink . I was told that the “pink” had memory…ie it would robound from a heel dent without creating a small delam. I built an 8’ 6" log using both white Dow and blue dow. The board was primed with straight epoxy , no thickener to keep the viscosity low , and penetrate the foam as much as possible.It did penetrate…not as much as EPS does , but it did penetrate enough to put a hard skin on the foam’s surface , therefore increasing impact strength…and creating a more than adequate bond between the glass job ( 2 layer of 4oz) and the primed xps… The application of the prime coat was by squeegee , using enough downward pressure to force as much as possible into the foam surface , then removing all possible resin off the surface with squeegee , then wiping with tight celled sponge brush. Although the board has not had a lot of use , I did ride it regularly for about a month…and my bro used it regularly for almost a year… its now a spare board , and someone grabs it for a wave every now and then…it has no heel dents so far, or signs of any delamination…I built this board about 8 years ago.

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This a great thread and in the distant past I posted some results on tests I’ve done. 

I have a climbing drum peel test setup and 4 point bend rig attached to a nice test machine (Lloyds 100K) so could put some numbers into these tests. (Although I suspect that Lemat could as well, it is always the time element!) Very happy to do some tests but to keep it relative to the results here would need to know a few more details. For me the time consuming bit is laying up samples, maybe my students could do it for me. Anyway I make the offer of time and equipment if it helps.

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Rikds!!!  Welcome back. 

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…

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Interesting.

Do you know/remember what the density and minimum compressive strength were for your DOW XPS foams?

What was your final sanding grit before you applied the epoxy pirmer?

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Thanks Rikds.  Do you know what the URL and/or the title are/were for that thread in the distant past.  I spent some time doing searches but struck out.  I would like to read those test results**…**

Absolutely, I welcome your participation in the testing.  There are so many potential panels with different variable combinations that could be tested.  Creating various test panel lay-ups can burn up a lot of time.  More test participants allow more data to be collected faster – the more the merrier.

I appreciate your offer.

What details do you want?

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Once again, cool stuff to see. A while back I was testing nylon I bought from a fabric store on eps. 

I vacuum bagged two types of nylon to the eps,(in a ziploc bag), which was sanded lightly with 180 grit.

The first was a ripstop nylon, which acted like peel ply, and came right off. The other type, was a 200 denier cloth, and the peel looked similar to your results. I originally wrote it off because I thought it should have pulled up more foam. Your results make me rethink that conclusion.

 

On another note, I would be curious if there would be any benefit to using gorilla glue, and a vacuum bag to adhere a wood veneer as the “sealer”.

When I have seen balsa put on, it was with a layer of 4oz cloth underneath. Which I am thinking makes a stronger laminate construction, so maybe the gorilla glue would be a bad idea. It would definitely adhere the balsa better to the foam, but I imagine the board would break in half easier. 

 Lemat any thoughts?

 

Also I have spare blue dow, and 2lb eps sitting around if you want to post up any other combinations you would like to test. 

Cheers,

Jason

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The blue and white were given to me by a friend that was buying it from Dow in Sydney (before they shut down) , so I didn’t get a data sheet. Blue/white , according to Dow’s tech guy were the same foam , just made using different colouring agents. The pink was different foam. Pink was being used exclusively by the guys in Byron , who were building the Bamboo Sunny Garcia boards back then…Unless Dow has changed their formula , the physical properties should be available on request…probably a doc sheet on their website…the shaped board was finished with standard gauze…I’m sure it was well worn 320grit gauze…the cured epoxy prime coat was smoothed off with 320 freecut…also , I used pigment in the prime coat for the bottom of the board , which made no noticeable difference.

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…Ive heard a few nightmare stories of the blue Dow shrinking inside a glassed board…and I noticed some quite severe shrinking and distortion on a block I had stored in my shed…no apparent problem with the board I have.

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Of the last 4 or 5 boards I’ve made, all except one has been blue Dow XPS foam. 3 are regularly used I don’t do anything special to make the bond of glass and resin stronger. I usually don’t bother sealing the blank either, just laminate the board the same way I’d do any board. If anything I’d have a little extra resin available for the laps, and use a brush to wet the foam before lapping the rails. I tend to keep the volume of resin conservative, so that little bit of resin brushed on the rails on XPS makes a better bond for the wrap. I still have a lot to learn about glassing, but without a teacher you learn things as you go along.

I’ve stripped a few XPS boards and I’ve had large chunks of foam break off at the rails. With EPS more foam will pull away with the glass becuase it’s made from small balls of foam mashed together with heat and pressure.

 

 


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