Adhesive for Refrigeration Panels

[exMaggieDrum]

My complete redo of my refrigeration boxes is one of the hardest projects I have done. It is getting along though and I am at a crossroads and rethinking how best to bond the interior panel skins at the right angle corners inside the freezer and reefer boxes. It will be a cold plate/spillover type system.

I had to completely remove all the old interior - open cell foam insulation and old painted plywood panels. It had too much "framing" on the inside under the panels so I removed most of that as well. I have had to rebuild with some new framing to screw down new panels. The gelcoat "paint" had cracked in the old corners and moisture got behind the panels which caused mildew and rot and the wet insulation was failing.

I got some "structural" pre-made 1/4" FRP panels from McMaster-Carr to line the interior but they are raw FRP on both sides and I did not want to put paint on top of them which would eventually flake off. So I also got some thin FRP panel from Home Depot which is white and shiny/bumpy on one side and smooth on the other. I intend to install the structural panels with flat-head screws to the framing over the new insulation.

Then I will epoxy the thin panels on top of the structural panels over the screws. The idea is to completely seal the interior so water/moisture cannot get in to the insulation (a mix of Cryogel Z and rigid extruded foam board anywhere new screws might go - e.g. cold plate holders). The Cryogel Z is another story for later. It has been somewhat of a nightmare from a mess point of view.

My idea to seal all the corners was to put in epoxy fillets at the right angles where the interior white/shiny FRP panels would meet. These will be fairly close tolerance so the gaps will not be large. The epoxy should bond well to the sanded/clean FRP panels. I was not going to put in fillets for the structural panels corners before I glued on the thin shiny panels. Once the white thin panels are epoxied to the structural panels the two become structural as well. This should be a strong box construction.

Smooth epoxy fillets would be durable, strong, and easy to clean although they would not be white (pigment will make them less strong and it doesn't work very well anyway). I don't mind the color but sealing and cleaning are very important.

Now I am wondering if the natural flex inside a boat will end up cracking the fillets. The panels will be screwed down to the boat interior structure but that will flex some any way. There will also be pretty extreme thermal changes which might cause contraction/expansion of the panels, e.g. bringing the interior down to freezing levels and then dethawing many times.

So I think some kind of flexible bonding would be called for if, in fact, the fillets would crack and fail. Then moisture would get in the insulation and that is a problem. The panels will be plenty strong without the fillets but the corners might not remain sealed. On another box I built, I glued on the same smooth FRP panels on top of rigid foam board. I used either 5200 or 4200 (can't remember from 15 years ago). It worked but repeated cleaning of it seemed to make it want to peel and it was harder to get "dirt" off of the softer surface.

I think the answer is No but would the epoxy fillets be flexible enough to handle the expansion/contraction and flexing? Are there other products to provide a strong bond that is durable, flexible, and easy to clean? I am now thinking that I will need to use one of the tried and true adhesives/caulks like 5200 to seal these corners. This is a permanent installation so removal of the adhesive caulk is not a concern. Any ideas?

[Terra Nova]

That pebble-finish pre-cast fiberglass is not a vapor barrier and is structurally weak, so should be over-coated with an epoxy finish. Better would be to glass the structural box with a couple layers of bi-axial set in epoxy, then painted with LP.

[Bill O]

May want to rethink using the bumpy FRP on the inside of your refigeration box. I have used the smooth and bumpy frp sheets in many projects during our refit, but draw the line around food items. Maybe that sweet smell will go away but until then the out gassing will permeate your food. You'll be reminded of the FRP every time you eat fatty foods/butter that have been stored in your fridge.

I'd rather have food grade epoxy with the added white pigment any day!

Bill O.

[exMaggieDrum]

Terra Nova - Thanks for the info. Interesting about it not being a vapor barrier. I would not have thought it might would be since it is regularly used for commercial kitchens and bathrooms. But the extruded FRP behind it should be I would think. My screw holes would be epoxied over it underneath if I do this so they wouldn't be either. But something to consider. I would have rather used a white colored FRP panel like rParts sometimes sells but they did not have any when I had to make a decision. And I don't know if it would have been a good vapor barrier either.

The previous LPU paint had failed on the box I took out so that was a huge problem for moisture intrusion. I'll have to consider that though. With the underlying FRP panel is there a specific reason that extra glass and epoxy should be overcoated on it before painting?

Either way I still have to corner issue to deal with. Any ideas on that?

Bill O - also interesting about the outgassing. Like most FRP panels it does have a smell to it and it is stronger than most. I did use it on another reefer refit and we did not ever notice a food issue. We might have just been lucky or our taste buds weren't sensitive enough. We did keep some raw vegetables in our old box and I would think it would be what would pick up the smell the most. I'll have to do a smell test on the panels I have in the shop. Thanks for the tip.

[SteveofGRACEII]

If you are really concerned about the epoxied panels / corners not having any flex you can use West Systems "G Flex" which we've been using for several years in areas that we know will have some amount of flex. It has held up in every circumstance.

[Seighlor]

I rebuilt my box several months ago and asked myself the same questions you are presenting. Ultimately, I settled on 5200 vs. the preformed fillets. All I can say is, so far so good.

[skipmac]

I rebuilt my box exactly the way you propose but only used the HD fg panels for under the top, to make a new lid, etc. and made epoxy fillets where they joined. However I also painted several coats of epoxy over the panel to seal in the odor and seal out moisture. No fiberglass smell and four years later it's doing fine.

[getyourbone]

Urethane Coating 1/2 order

And I believe it comes in a couple different volumes as well as kit form with other materials.

I believe this would fit the parameters you are requesting…

Unbelievable stuff! Super super durable! Extremely abrasion resistant! I would say it’s pretty easy to clean. Flexible.

call them and see what they think?

[stnick]

I have done the similar project on a morgan 384. I to gutted the box.used Mc Master– Carr
Insulation and home depot FRP panels. I did use Tievick house wrap as a vapor barrier . I also used a divider and spill over design for cold from the holding plate. I used west system 6x10 for glue for the panels and corners.
Now my wife hated the smell of poly that would not go away easily !
I was forced to 2 part epoxy paint the inside and that did the trick. Im in Florida and my frig can get to 28 and my freezer side can get to 15 degrees. Lee tarpon springs fl

[stnick]

Originally Posted by stnick

I have done the similar project on a morgan 384. I to gutted the box.used Mc Master– Carr
Insulation and home depot FRP panels. I did use Tievick house wrap as a vapor barrier . I also used a divider and spill over design for cold from the holding plate. I used west system 6x10 for glue for the panels and corners.
Now my wife hated the smell of poly that would not go away easily !
I was forced to 2 part epoxy paint the inside and that did the trick. Im in Florida and my frig can get to 28 and my freezer side can get to 15 degrees. Lee tarpon springs fl

i also drilled 3 inch holes thru the divider wall one down low and opposite corner toward the top. I find i can control the spill over temp by using a insert cap when it it just get too cold in the frig .
I start a cruise with 10 pounds of DRY ice in each bottom and another 10 pounds of ice chips on top . The dry ice will not let the cubes melt for 12 days or so ! A big help in the florida summer heat !

[Typhoon]

Yes neither of those fiber boards will make a good vapor barrier , use 5200 on the seems as neat as you can because you wont be able to sand it . Forget about that pebble home depot crap if you already have a bare 1/4 fiber board . Get it all sealed up and paint it with epoxy . use a few coats to get enough build to create a proper vapor barrier . Then let it dry and dry , you may find a bad taste in your foods from the off gassing once you start to use your box . If you do then go to a aquarium supply store and get yourself some activated carbon , put it in a old pillow case and throw it in your fridge , it will take out all the solvent smell. This process may take months but it works , just leave the stuff in there and forget about it for a while . I buy it by the gallon, works for a very long time .

https://www.thespruce.com/activated-...uarium-1380929

Regards John.

[Bill O]

Originally Posted by ColdEh Marine

Then let it dry and dry , you may find a bad taste in your foods from the off gassing once you start to use your box . If you do then go to a aquarium supply store and get yourself some activated carbon , put it in a old pillow case and throw it in your fridge , it will take out all the solvent smell. This process may take months but it works , just leave the stuff in there and forget about it for a while.
https://www.thespruce.com/activated-...uarium-1380929

As a chemist with a sufficient amount of a toxicology background, this doesn't sound like the best idea. It maybe simple, but just because you can't taste it after awhile it could still possibly be harmful at low levels. IMO you'd be better off with a pigment in food grade epoxy (that has no solvents).

Bill O.

[Cheechako]

I would not use epoxy fillets on the corners. I think you are right, they are brittle and also I doubt epoxy will stick to the pebble finish stuff well anyway. I would simply use a quality white caulk. Me I'm a 5200 guy. I used it on a couple of fridge liners for the corner fillets, but I used Formica liner. It's a pita to cut though. Epoxy has the worst lingering smell of damn near anything. Polyurethane caulk (5200) is intended for sanding and painting BTW, but just make a clean fillet with your finger.
I would think that white pebble stuff would be fine in your fridge. As you say, it's made for bathrooms. Too bad you already bought some, I have a sheet or two here that is 10 years old...and I'm not far from you...if it did smell (I never smelled anything) it's certainly gone now!

[exMaggieDrum]

This project has been quite the learning process. These are all great comments!

SteveofGraceII - G/Flex sounds like it would be an excellent choice for the panel bonding at the corners, especially the 655. It is thickened already so would be easy to use like the 610.

Sieglor - I did some more research on the adhesive caulks and based on that I think I would choose 3M 4000UV instead of 5200. But I know that 5200 worked for me in my other box. But now I am leaning towards the West System 655.

Skipmac - I am beginning to think I have not thought through the issue of smell and water vapor penetration. I think I will try and seal every panel inside the box with three coats of epoxy. I assume that the epoxy coating of a 30x22" flat panel would not be damaged over time by freezing/thawing contractions and expansions. For some reason that seems to be one of my inner bugaboos. It may not be a problem at all though and I am just overthinking it.

Getyourbone - I live in the same town as the guy who makes and sells the urethane you linked to. A good friend of mine works there as a part time instructor. I'll ask him about that. I think it is clear and I really would like to have a white (or light) color inside. Which is the other issue I am trying to get to the best answer for.

stnick - What 2 part epoxy paint did you use? I want white if I can get it. So long as it is flexible enough to live inside a freezer and is not toxic to food living in there at the same time in both boxes. I will be using a spillover plate similar to what you did.

ColdEhMarine - You are a pro in building boxes so I appreciate you chiming in. I am leaning towards West 655 now but I am going to call them tomorrow and pick their brains about it. I do have some activated charcoal I was going to use to repack a holding tank filter but I decided to change the whole system and I pulled out the filter. But Bill O just added a note.....

Bill O - so the question is which food grade epoxy paint is there. I did a quick search and found some but need to do some more digging.

Other comments are welcome. Thanks all!

[Typhoon]

Of course food grade .

And yes you can use 665 but it is messy. The Aerogel was messy to wasn't it . I hate working with that stuff.

POTABLE WATER Epoxy Paint 603.435.7199

Regards