Alternate adhesive testing for PMF

[MatTech]

I don't know if this adhesive is available in the US but I picked up a gallon for testing on my toyhauler build. I searched and it doesn't appear to have been discussed.

I was looking for an alternative to TB2 for the PMF exterior of my build since TB2 really isn't made to adhere to XPS and I don't really want to settle for good enough. The Durapro adhesive is made specifically to bond XPS to a porous surface and is a latex based material so latex exterior paint should bond well to canvas impregnated with it.

The adhesive is the consistency of drywall mud and smells like acrylic latex caulking. It goes on thick but still oozes through the canvas. When dry (24hrs) it is rock hard and bites into the foam. I have also begun testing it as a filler to smooth the outside of my TTT.

As you can see in the photo it does shrink when applied thick to a screw hole in the foam but I think a second coat will take care of that. I'm going to submerge the test piece of PMF in water for 12 hrs today and we will see the results of that tonight.

Let me know what you guys think.

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[linuxmanxxx]

Drying hard does it get brittle or maintain a bit of flex since bouncing down a road would stress it.

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[GPW]

NICE!!! Thanks for the Info Mat !!! Something else to try !!!

[MatTech]

When dry it's almost the consistency of drywall plaster, it has a bit of flex to it before it breaks off. I also forgot to mention that it stands much like plaster.

I've attached a pic of the PMF test piece which I lightly sanded and is now sitting at the bottom of a bucket of water. I'll let you know the results tonight.

I don't see the lack of flexibility being a problem since as with a TB2 application the strength comes from the fact that it can not move. After I remove the test piece from the water I will slice it in half, one piece I will try to delaminate the canvas and the other i will try to break the foam under the canvas.

Any other test ideas?

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[tony.latham]

I don't see it on the two usual suspect's pages –Lowe's and HD. Where'd you get it and what was the price?

I would think it would need to have some flexibility because of the expansion/contraction of XPS. But I don't know.

Tony

[MatTech]

I got it at Canac, it's a local hardware and lumber store. $30 Cdn per gallon.

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[MatTech]

Looking at the technical data sheet for the adhesive it says that it has excellent water resistance when dry. The safety data sheet notes that it contains 30-60% limestone so I don't imagine that it will be overly flexible. Being that it is made for foamboard I don't think that the natural expansion and contraction would affect the bond. We will see.

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[John61CT]

Glidden Gripper primer is the bomb, from my reading the standard for comparing anything new, rather than TBII

[MatTech]

John,

thanks for the advice. I'll definately look into that. Just to be sure you are saying that it works well for canvas direct to foam? The main motivation for me trying to find something other than TB2 is that it really isn't made to adhere to XPS. If this Gilden Gripper is the stuff to use I'll see if I can find it. I still have lots of time before I move to skinning so I can play around with more tests.

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[MatTech]

Well, after a good long soak in water I have learned some about this adhesive. The bond with the foam was unaffected by the soak and it refused to let go of the foam. The canvas however did manage to absorb water and this did affect its bond with the adhesive. After ripping off the foam the canvas was clearly saturated.

It should be noted that no top coats were applied to the PMF, just the adhesive underneath the canvas and what managed to seep through onto the outside. I think I will make up another test sample with a watered down mix to ensure full impregnation of the canvas and top coat it with the same diluted mix. I don't really want to coat it with latex paint because then I would really just be testing the paints effectiveness at stopping water ingress.

I will also fully saturate a separate piece of canvas and let it dry to test flexibility.

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[John61CT]

John,

thanks for the advice. I'll definately look into that. Just to be sure you are saying that it works well for canvas direct to foam? The main motivation for me trying to find something other than TB2 is that it really isn't made to adhere to XPS. If this Gilden Gripper is the stuff to use I'll see if I can find it. I still have lots of time before I move to skinning so I can play around with more tests.

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Applying canvas to foam is so far from the mainstream, whether something is "designed" for that purpose or not is IMO irrelevant.

The question is how well does it actually work in practice, and many dozens of builds documented here have proven that it does so very well.

Everyone loves a pioneer testing out new stuff, and of course the community is grateful, that's how scientific progress "goes Boink".

Personally I prefer to avoid the arrows in the back, and want to follow more well worn paths.

https://www.google.com/search?q=site%3A ... en-gripper

[pchast]

Gripper worked very well for me.

The foam needed to be prepped by cleaning the surface, either sanding or puncturing it too. Then I rolled the latex paint onto the canvas and let it set while I rolled a thick coat onto th e foam. The canvas was fitted into place and smoothed down. About 24 hours later it had dried to a set.

With one piece it rained outside. That took 3 days to finish drying with the higher humidity.
I wonder if any other latex primer would work as well.

[MatTech]

I am more of the sort to find my own path through the wilderness lol.

I can't seem to source the glidden gripper here in Canada and I don't know the next time I'll be down stateside. Actually it will probably be this summer and I'm supposed to be towing the finished trailer down with me.

I have a relative that comes up from NJ pretty frequently and I'll see if she can bring some up. For now I'll continue on with my testing of locally available products.

Thanks for all the input everyone.

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[MatTech]

It appears that Dulux is the canadian version of Glidden, they have a product called weatherguard exterior primer that is 100% acrylic. I wonder if it's the same product?

https://www.dulux.ca/pro/products/prime ... ior-primer

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[GPW]

Technically all those acrylic primers are pretty much the same … Acrylic polymer as the binder and Titanium white for the pigment … and really , acrylic paint should work the same ( even oops paint) … more testing !!!

We’ve done Foam to Foam adhesion tests with TB2, Gripper , and both took forever to dry completely …( couple weeks at least on Big areas ) Foam to Canvas is so much thicker , especially like I did it in the summer …

JMH testing , we had TB2 dissolve over time due to constant water exposure ( morning dew) , although it took several years … The Gripper never did … holds fast ...

There’s a Big difference between water resistant and water proof … we had to actually experience a Failure it to really find out …