Glidden Gripper vs PPG gripper

[fishboat]

Fishboat, may I ask.. In your opinion does the Pro-Cryl Primer have the attributes we are looking for?

I have now found the SDS on it, yet don't know enough to understand..



I posted SW's product sheet earlier.

SDS:
https://www.sherwin-williams.com/docume ... 467305/US/

RJ..Looks like nice stuff. S-W was one of our customers(we'd sell them the base emulsion and additive polymers that were better than what they could figure out to make..our products were complex enough in processing that they couldn't figure out how to make them themselves). When I need paint..I buy S-W most often. The PDS doesn't mention wood or other substrates..whether it would be good with foam..only experimentation can tell.

The carcinogen warning is relative to the liquid/contents. This is an on-situ 2 pack coating..I'd guess an acrylic-epoxy. Once it's applied and cured the carcinogen concern goes away. Epoxy-fiberglass work isn't terribly friendly & yet people use it everyday. I'd wear gloves & have plenty of ventilation with the Pro-Cryl and not worry about it..speaking only for myself, YMMV.

[RJ Howell]

RJ..Looks like nice stuff. S-W was one of our customers(we'd sell them the base emulsion and additive polymers that were better than what they could figure out to make..our products were complex enough in processing that they couldn't figure out how to make them themselves). When I need paint..I buy S-W most often. The PDS doesn't mention wood or other substrates..whether it would be good with foam..only experimentation can tell.

The carcinogen warning is relative to the liquid/contents. This is an on-situ 2 pack coating..I'd guess an acrylic-epoxy. Once it's applied and cured the carcinogen concern goes away. Epoxy-fiberglass work isn't terribly friendly & yet people use it everyday. I'd wear gloves & have plenty of ventilation with the Pro-Cryl and not worry about it..speaking only for myself, YMMV.

Thank you for response! My testing is showing a very good bond to foam. Decent penetration in cloth, yet better when I cut it 20% (or so) with water.

Please you tell me if this makes any sense, but so far my best test/system is to prime the foam and let it dry (24hrs) then apply the cloth with diluted PC. When doing both at the same time I get a poor adhering to the foam.

[fishboat]

...My testing is showing a very good bond to foam. Decent penetration in cloth, yet better when I cut it 20% (or so) with water.

Please you tell me if this makes any sense, but so far my best test/system is to prime the foam and let it dry (24hrs) then apply the cloth with diluted PC. When doing both at the same time I get a poor adhering to the foam.

Sounds like a reasonable approach. You might consider a little sooner than 24 of dry time(somewhat of a wet-on-wet or wet-on-still tacky approach), but if it's working...

The PC is reported to be a curing primer..this is significantly different than the normal non-curing, thermoplastic-type products.

Another wiki.. "curing" and "crosslinking" are interchangable terms:
https://en.wikipedia.org/wiki/Cross-link

The PC is said to take up to a month or two to fully cure. If the 24hr dried coating dissolves and mixes with the subsequent diluted coating this would, chemically, would be very good as the two coatings will eventually crosslink & form a very strong composite. If the 24hr dried coating does not chemically mix with the new diluted coat(it may not..depending on how set up the 24hr coating is) then you may still have a good system(based on mutual adhesion), but not as strong as the one described above.

I think I would try some earlier recoat testing to see if a system can be worked out. Say..1hr, 2hr, 3hr, 5 or 6 hrs 10hrs... then let the coating dry and cure for a month at 75 degrees and do some pull testing to see how it performs.

[RJ Howell]

...My testing is showing a very good bond to foam. Decent penetration in cloth, yet better when I cut it 20% (or so) with water.

Please you tell me if this makes any sense, but so far my best test/system is to prime the foam and let it dry (24hrs) then apply the cloth with diluted PC. When doing both at the same time I get a poor adhering to the foam.

Sounds like a reasonable approach. You might consider a little sooner than 24 of dry time(somewhat of a wet-on-wet or wet-on-still tacky approach), but if it's working...

The PC is reported to be a curing primer..this is significantly different than the normal non-curing, thermoplastic-type products.

Another wiki.. "curing" and "crosslinking" are interchangable terms:
https://en.wikipedia.org/wiki/Cross-link

The PC is said to take up to a month or two to fully cure. If the 24hr dried coating dissolves and mixes with the subsequent diluted coating this would, chemically, would be very good as the two coatings will eventually crosslink & form a very strong composite. If the 24hr dried coating does not chemically mix with the new diluted coat(it may not..depending on how set up the 24hr coating is) then you may still have a good system(based on mutual adhesion), but not as strong as the one described above.

I think I would try some earlier recoat testing to see if a system can be worked out. Say..1hr, 2hr, 3hr, 5 or 6 hrs 10hrs... then let the coating dry and cure for a month at 75 degrees and do some pull testing to see how it performs.

Again, Thank You!

I will setup a test board to report to the group. With what you have said and what I'm reading (and ready to canvas), I see priming again and going 2-4hr dry and canvas. Product sheet I believe is saying (max) 4hrs.. even though I had very good success with longer, I'll go with that.

[GPW]

Short Quote … “ The PC is said to take up to a month or two to fully cure. “ We found this out when using primer ( gripper) for assembling our Foamie planes …. The longer it dried the stronger it was … and that was Foam to foam ...

[tomhawk]

I am wondering if some of the testing of adhesives for bonding PMF is misleading.
The most common test is whether the fabric can be ripped off the foam where it was glued (panel A in figure). In some cases the foam fails and fragments remain attached to the fabric.
This does allow for comparisons of adhesives.

However, In no case I am aware of will a loose edge of fabric be under this type of stress. Instead fabric edges will be glued to wood or to each other making a continuous surface. There is no question fabric glued to wood or fabric is very strongly adhered.

The forces on the glued fabric/ foam structure will be produced by bending surfaces not ripping off fabric. The glue will have to fail by the fabric fracturing along the surface of the foam rather than fail along a much smaller zone seen with ripping off the fabric. Testing should apply forces parallel to the plane of attachment between the fabric and foam not perpendicular to it.



I am wondering if a better test might be what is depicted in panes B & C above. A portion of foam is covered with the test glue and fabric. A bending force is applied to the structure placing horizontal stress on the PMF layer until something fails.

If the glue delaminates then it has failed the test.
If the fabric or foam is damaged first the the glue is successful.

I suspect many glues/primers are going to work just fine in this test. The glue only needs to not be the limiting factor in this structure. Good enough is no worse than better.

Tom

[RJ Howell]

I suspect many glues/primers are going to work just fine in this test. The glue only needs to not be the limiting factor in this structure. Good enough is no worse than better.

Tom

I'm finding most exterior primers don't work well, yet that's me and my experimenting. One of the first tests I did was to see just how strong the bond would be on a angle. I took two pieces of foam, not glued, and did a strip enforcement on a 90 degree inside corner. The cheaper primers I was able to tear the sections loose. Now, all bent inwards fairly easily, yet with a better primer, it took quite a bit of force to break that connection, some I could not physically break. With both inside and outside of each seam/joint being done, and glued, it would surprise me if you could break it on an outward test with a good primer.

I personally see the tear test as important. It shows the bond in such a way that probably wouldn't happen in real life. I also believe that if you placed two pieces side by side and attempted to tear them apart, sideways, you'd find it very difficult and probably beyond human strength.

With that said.. It would e a good test for you to go through.
Would love to hear your results.

[John61CT]

Wiki:

Strength is expressed in terms of the limiting values of the **compressive** stress, **tensile** stress, and **shear** stresses that would cause failure. The effects of **dynamic loading** are probably the most important practical consideration of the strength of materials, especially the problem of fatigue. Repeated loading often initiates brittle cracks, which grow until failure occurs. The cracks always start at **stress concentrations**, especially changes in cross-section of the product, near holes and corners at nominal stress levels far lower than those quoted for the strength of the material.

_____
Each of those "different strengths" has its own tests.

But with glue we're looking for adhesion.

The tensile strength of the **sheeting glued** will become the limiting factor, once the glue is doing its job.

Some use insect screening for both tensile strength and puncture resistance, rather than canvas or bedsheets.

Plastic "dog-proof" screening will be different from the metal materials. Elongation /elasticity is yet another factor, orthogonal from the various types of "strength".

[RJ Howell]

Some use insect screening for both tensile strength and puncture resistance, rather than canvas or bedsheets.
.

I tried some fiberglass tape, then fiberglass screen in a test that I did not mention because it failed so badly.. The weave is too loose. Bedsheets worked so much better, tighter weave. Canvas being better again due to better material and tight weave. Even fiberglass cloth is a higher weave.

Importance here is the weave and how tight it is, quality there of and of course the glue (in my case primer). Glue has to penetrate, absorb and adhere.

By all means, test your theory and let us know your results.

[JagLite]

Hmmmm....
Nothing new reported on the subject in months.
It's been very interesting.

I'm reading through a lot of threads trying to get the latest, most up to date successful information on materials: fabrics, glues, and paints.
I've done a little playing with testing by sticking fabric to foam board and I am impressed with how much strength there is.

Most (all?) of the testing I've read here, and what I have done, is peel strength, not shear, compression, or tension.
That is a very important test for trailer surfaces because the stronger the peel strength is the less likely the fabric will pull loose or delaminate from the foam.
We do not want our surfacing (fabric to foam) to delaminate because they are what gives the foam trailer walls and roof its strength.

The best, cost no object, covering will be epoxy-carbon fiber but that is way beyond the budget of probably most of us here on this forum.
After CF I would place epoxy fiberglass/polypropylene/polyester woven fabrics, and after them the non-woven fabrics of the same materials.
(Landscape/weed control fabric is an example of a non-woven poly fabric)

However epoxy-fabric composite seems like overkill for a tiny trailer built on a budget.
Which is why I am interested in using paint/glue to bond the fabric to the foam.

Shear strength is quite dependent on the fabric used I believe, with the glue/filler/paint adding only a little strength.
Shear strength is what the corners need. And why it is a good idea to have multiple layers on the corners (wall to roof, etc).
Compression and tension strength comes into play when something impacts the foam and again I believe the fabric will be what determines the extent of damage.

Hopefully there will be more posts on this thread with results of peel strength tests of other paints and glues on foam.
Ideally, something cheap that will stick fabric to the foam like epoxy.

[John61CT]

peeling of course no one wants

but actually basing the materials / adhesive pairings on that factor to me is wrong, since we aren't actually exerting any significant forces that way in normal use,

would only be relevant after puncture damage or tensile failure, 90° angles buckling

"good enough" for peel stress is OK for me

Puncture resistance I think requires expensive fabric, and IMO the whole point of cheap is easy repairs, even in the field.

Light canvas / heavier dropcloth is a done deal IMO, good enough for the tensile and shear loads involved for the smaller structures we're talking about.

Bigger ones at high speeds, then support framing comes into play and the PMF goes back to a "mainly skin" tech no longer as structural.

The big missing link now is replacing the genuine GG, maybe the new PPG formulation **is** "good enough", or

maybe we're in pioneer mode once more, starting from scratch

[GPW]

Tomhawk … JMHO , this was a better test for our trailer needs …

[RJ Howell]

Jag, for me testing different paints (and TB2) I found differing results in just the peal test as in adhesion and stiffness. One would be material stiff, yet lost adhesion. When another would adhere nicely, yet felt softer.. I liked my Pro-Cryl from Sherwin-Williams (it is not cheap), it hit the balance of both. I see the peal test as a pretty good way of testing.

I do like TomHawk's test shown above. This is a great way of determining strength of the foam once covered.

Only MHO and how I went at it for my build.

[John61CT]

To me, retaining some flexibility would be a good thing, too much stiffness not.

Talking more about the compression/puncture dimension, not tensile, that would be handled by good adhesion.

[JagLite]

Good points all.

I looked closely at that picture and it appears that the foam did the job.

The sledge hammer wasn't damaged!

Locally I can get two grades of Foamular, the 150 (15 psi) or the 250 (25 psi) (compressive strengths).
I can't think of any advantage to using the weaker 150, can you?
The 250 is $41 a sheet (2"x4'x8') and the 150 is $37 same size.
I need 9 sheets for my project.