Alternate adhesive testing for PMF

[MatTech]

I guess I'll try and find an exterior acrylic primer here in quart size and try that out as well. Thanks for the advice.

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[MatTech]

So you're probably gonna think I'm crazy with all these ideas but I've got another test going... I was thinking about the point of elasticity that was brought up and I remembered tiling my walk in shower a few years back.

I used a product called mapelastic HPG to seal the concrete backer board before installing my porcelain tiles. It's basically like really thick paint that turns into a very flexible rubber membrane once dry. I remember the stuff being just awesome and after a peek in my basement sure enough I have most of the second gallon I purchased leftover.

The stuff is really quite expensive so there's little chance I will use it to coat the trailer but I wanted to give it a try anyway. If it works well maybe I will do the interior of the wet bath with the gallon I have left.

With liquid waterproofing membranes on my mind a little searching indicates that there's quite a few of these products available. Another one that interests me is liquid rubber polyurethane deck coating, liquid rubber makes an RV roof liquid membrane but I would bet the polyurethane would bond better to foam and be more durable.

Anyway, just having a little fun on a snow day

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[GPW]

( A Proper Quote ) “ So you're probably gonna think I'm crazy with all these ideas but I've got another test going..”

They called us CRAZY for many years for even bringing up this Foamie idea … Testing is what it’s really all about …

[linuxmanxxx]

How's the diluted test coming?

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[MatTech]

Dilution of the durapro adhesive was an epic fail. It basically turned into a lumpy goop that never dries. If I don't end up using it for my PMF exterior I will use it as is for bonding the 1/8" luan on the inside.

I did thoroughly soak a small piece of canvas which is now drying so that we can see the flexibility. Should have results of that tomorrow.

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[MatTech]

First test of the Mapelastic HPG. I cut the sample in half because I want to see how paint will adhere to the cured membrane. Below are pics of the separation test, it was hard to peel off and there is foam particles embedded in the membrane after removal.

Only 1 real chunk of foam was ripped out as the side was ripped off in more of a shear motion that peeling. I would bet that a deeper sanding of the surface would improve the bond even more. This piece was only lightly scuffed with some mesh drywall sandpaper.

In the application manual for the product they note that fiberglass mesh can be embedded in the membrane for strength and to improve out of plane movement resistance. Fiberglass mesh for door screens can be purchased very cheap and I've got some laying around so that will be the next test.

This stuff is over $60 Cdn a gallon and they state that at 1mm thickness it should cover 40sqft so unless I can find a better price and buy 5 gallon buckets, this stuff will only be used for the wet bath walls.

For those of you who have been using TB2, what kind of coverage were you getting per gallon? Not for one coat but for the finished PMF panel. This info will help me make a decision.

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[MatTech]

Even more info

I contacted The liquid rubber company here in canada about the application of their products for my situation and here is the reply:

"Hello Tim
I would recommend our Liquid Rubber RV Roof Coating or Liquid Rubber Polyurethane Deck & Dock Coating for your application.
The Liquid Rubber RV Roof Coating is similar to the Liquid Rubber Coloured Waterproof Sealant but modified to finish tack-free. This should leave you with an acceptable hardness, while maintaing elasticity (1500%).
If hardness/wear resistance is your primary concern, go with the Liquid Rubber Polyurethane Deck & Dock Coating.
I am attaching a data sheet for the RV and the Polyurethane.
The RV has a recovery (when stretched) of 99%, but I do not have a value for the Poly (I would assume it is less)
Both products are UV stable and waterproof.
(waterproofing properties are maintained after recovery, but will be affected while being stretched ,as the coating is physically thinner. I do not believe the value difference will be significant or that this is especially relevent as elongation is simply to endure thermal fluctuation and other (i.e. wind) normal movements)
Please see our Geo Textile Fabric for fibre-reinforcement.
Bond to the XPS will not be an issue, this is a common application.
If you provide an address I can send you a couple of cured samples, but liquid samples are not available at this time.
Please let me know if I can be of further assistance.
Have a great day!
Trevor"

They will be sending me some cured samples but this product seems to fit the bill for exactly what I want. With fiberglass mesh embedded in the polyurethane it should be super tough and remain flexible. The polyurethane formula even comes in a few colours and is UV stable so no paint required at all.

Thoughts?


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[John61CT]

Looks like PMF is going commercial!

Glad or sad, I'm not quite sure. . .

[MatTech]

So back to the original topic, the durapro adhesive. The flexibility test piece is now dry. The answer to the question is that it really is quite flexible when saturated into the canvas. I was able to bend it back and forth with no problems. If you make a sharp 180 degree bend it will crack however but I'm not sure there's any material that wouldn't.

This stuff is moving back into my list of possibilities. I really like the idea of using a liquid waterproofing membrane embedded with either fiberglass mesh or geotextile but it would be far cheaper to go this way with regular canvas and exterior acrylic paint.

I think I'll throw a coat of paint on this and set it aside with the painted mapelastic hpg sample.

Don't mind my cut up gorilla glue stained fingers in the pics lol.

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[charlesbros]

The question remaining for us up north in Quebec is how will it handle the cold weather.
Thanks for your all your testings, it will, one day, help me to build my dream....

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[MatTech]

I guess with the temps currently fluctuating here from -5C down to -30C in a 24 hour span this time of year I should leave a couple painted samples out in the 12' snowbank beside my garage. Maybe even do a flex test on a cold day.

Maybe I'll try that next week. If I don't have to shovel off my roof. Again.

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[MatTech]

Painted Mapelastic HPG sample is done!

All I can say about this stuff is WOW. I put two coats of acrylic exterior paint over the blue membrane and let it dry. A peel test of the side corner showed the same excellent bond to the XPS as before. I then started gently scratching the surface with my fingernail to see if the paint would peel showing the blue membrane, it did not.

Then I started getting rough trying really hard to peel the paint with my fingernail until I bent my nail backwards (ouch). Then I got mad and started at it with a butter knife in a scraping motion, nothing again. Then I started hammering it with the handle of the knife and only light surface dents where the foam had compressed underneath without harming the membrane.

I am really impressed and this is definitely the product I will coat the interior of my wet bath with. If the liquid rubber samples I receive demonstrate the same qualities then I will be ordering 5 gal of it with the geotextile they suggested to coat the exterior of the trailer.

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[MatTech]

I changed the name of the thread to better suit the content which is ever evolving

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[MatTech]

Liquid Rubber samples are here!

As promised I received the polyurethane liquid membranes from Trevor at Liquid Rubber. The samples are very tough and remind me of stiff synthetic leather.

The white sample is PU-100 and supposedly has a 400% elasticity rating. It is noticeably more flexible than the deck coating. The geotextile embedded in the membrane is more visible on one side than the other. After careful examination I believe the more textured side with small air bubbles visible in the surface is the outside. I have emailed Trevor to confirm this, I would rather have a surface finish like the other side where the geotextile can barely be seen and there are no surface imperfections but I will find out from Trevor if this is possible

The brown sample is the deck coating and there is a visible seam where there is no geotextile embedded for about an eighth of an inch. I'm not sure if this was on purpose to demonstrate the products inherent strength even without the embedded geotextile or not. This product claims 200% elasticity and it can literally be creased over onto itself and not crack. Stretching it at the seam where there is no geotextile is possible and it does recover its shape once tension is released. Once again the embedded geotextile is still visible in what I suspect is the surface finish but there are far fewer imperfections from air bubbles.

Both samples are very scratch resistant and only metal objects seem to leave any marks.

I will let you know more when Trevor gets back to me about which surface is actually the outside. So what do you guys think?

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[John61CT]

To me checks out great, as an outermost UV / waterproofing layer.

As for gluing canvas or embedding direct into foam, who knows, you'd need to test.

Cost likely much higher compared to Gripper then oopsie paint, but obviously not your top priority.

Be the pioneer!