Why didn't my silicone stick?

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IrregularPulse

IrregularPulse

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I bought the 108 Silicone from Mc Master car to join a SS washer to my Plastic cooler. Cleaned both services with rubbing alcohol, applied a bead of silicone around washer, placed face down against flat plastic surface, and put a few pounds of weight on top. Cure time said 20 mintes. I let it go 45 and then then I grabbed the washer, it lifted up with 0 resistance and there was a cured bead of caulk on it.

I bought the 108 HERE. Should adhere to plastics and metal like it says right? Specifically Stainless Steel and plastic.
 
I don't know what kind of plastic a cooler is made from, but I've never gotten anything to stick. I want to seal the hole where my pre-chiller lines go in, I tried silicone, epoxy, jbweld, etc. Nothing. Sticks to the copper fine, just not the cooler plastic.

I'll be watching for anyone else's solutions...
 
The only epoxy I found that sticks to plastic well is aquamend. Silicone does not stick to much of anything including itself. They make special cleaners / pretreatment solutions to make it stick to stuff.
 
Probably work better if you sand the surface of the plastic before trying to stick anything to it. The plastic's surface will be very smooth, which doesn't give adhesives anything to grab a hold of.
 
Just an idea, but most of those molded plastics have a "Mold Release" coating on them, that prevents them from sticking to the molds...

Note: I have no experience trying to stick anything to coolers... but...

Try a fine grit sandpaper and get below the "Non-stick" shinny coating around the area and try again. This should serve 2 purposes, 1. remove the non-stick coating and 2. give a roughened surface for the silicone to stick to. (much on the principle of paint to a smooth surface vs a sanded one)

Hope this helps and good luck!

Cheers,
Mark
 
I had drilled my heating element hole too big and want to reinforce it with a SS washer I had drilled out to fit snog around my element threads. It will serve to reinforce the coolor bottom as well. Just need i tot seal.
 
I'm gonna try and rough it up with some 4-600 paper over the weekend. Sounds it it just is too slick to grab onto. When all said and done, that joint will be secured together by the Nut pulling against the hot water heater element. I just wanted to make sure it was sealed first.
 
Nearly 11k posts but you can't properly drill a hole...I recommend you start spending a little more time away from your computer.

Just busting balls :D :mug: :ban:
 
600 grit to *rough it up*?
how about 100?
bigger scratches will give any sealant more "tooth".
 
20 minutes?? Spec sheet says it begins to harden at 20 min w/ a cure at 24 hours. +1 on using 100 or 60 grit on the plastic to give it a little tooth. 600 is just about like polish.
 
I assume that you're placing your heating element in a cooler. I just looked up the type of plastic for the 10 gal ones, and they are made of polyethylene. Pretty much nothing will stick to that or polypropylene. I have tried to use DP8005 as well as many of the other newly developed adhesives for poly-olefins (this type of thermoplastic). Not only do they smell absolutely horrible, they didn't seem to adhere relatively well when I used this in an application at work. I would use a DIY bulkhead fitting setup, so you can play around with the washer/o-ring size to get the fit right.
 
brewmonk said:
600 grit to *rough it up*?
how about 100?
bigger scratches will give any sealant more "tooth".
Click to expand...
It doesn't need giant teeth, just a small area to grab.

GreenMonti said:
Give this a shot. The fact that it is a food grade container your hard pressed to find something to seal to it.

http://www.stealth316.com/2-dp8005.htm
Click to expand...
That stuff is only rated to 212. I'm thinking the element itself may be hotter than that. The stuff i have is rated to 400-500° and is foodsafe.


bluecarpetsample said:
I assume that you're placing your heating element in a cooler. I just looked up the type of plastic for the 10 gal ones, and they are made of polyethylene. Pretty much nothing will stick to that or polypropylene. I have tried to use DP8005 as well as many of the other newly developed adhesives for poly-olefins (this type of thermoplastic). Not only do they smell absolutely horrible, they didn't seem to adhere relatively well when I used this in an application at work. I would use a DIY bulkhead fitting setup, so you can play around with the washer/o-ring size to get the fit right.
Click to expand...
It will be secured with a nut and gasket on the element itself. I just wanted this extra layer between the washer and cooler.
I'll rough it up and try again. If it doesn't hold it'll be fine with just a layer of it adhered to the washer like a gasket. Just won't be a permanent connection like I'd planned.
 
freddyb said:
Nearly 11k posts but you can't properly drill a hole...I recommend you start spending a little more time away from your computer.

Just busting balls :D :mug: :ban:
Click to expand...

I'd love to but my boss might get mad when I phone goes un-answered because I'm busy drilling holes in the back:)
Unfortunately it was one of those 'try and do it real quick while at work' things and then came the 'you retard' moment immediately after. It's the fact that I did know better that hurts the most :mug:
 
I'm pretty sure they are Polypropylene which is VERY slippery. The outside shell is Polyethylene. I have gotten Weldon #16 to stick once it was scuffed, but that's more of a plastics cement rather than a flexible sealant. If you're going to use mechanical means to hold it all together, it really doesn't matter if the silicone adheres. I'd do a gentle squish to flatten it out, but then allow it to act more like a gasket when you tighten the element's nut down.
 
IrregularPulse said:
That stuff is only rated to 212. I'm thinking the element itself may be hotter than that. The stuff i have is rated to 400-500° and is foodsafe.
Click to expand...

Sorry, I should have been more clear. I only posted that link for the info on Polypropylene. Showing the difficulty of getting anything to stick to it.
 
From experience in the aquarium hobby, silicon is great on glass, but it will peel right off plastic no matter what you try.
 
I reapplied it last night after taking a dental pick to the plastic. If it sticks it sticks, of not, it'll be a gasket. I put it on there, fed my element through and tightened it up with the 1" SS nut on the inside. I'm gonna do a leak test on it tomorrow night. That'll give it 48 hours to setup.
 
What happened here? I hate to resurrect such an old thread but this is something i'll be doing soon myself.
 
yea, it doesnt really matter if it adheres to the surface, its the compression between the surfaces that will make the seal.

put the silicone where you want it and assemble everything very loosely, then once it sets, tighten the connection and clamp down on the silicone.
 
From what I've read, only exotic and expensive special epoxy type adhesives will work with polyethylene. I do agree that you can make a gasket with silicone and it won't matter if it adheres or not. It will get squashed like an O-ring on a weldless fitting.
 
I don't remember what happened with the cooler, but I currently have a 7G Aluminum pot with a weld-less element through the side for a jKarp clone, 2 keggles with 1" welded couplers for a larger future version and a10G igloo cooler with a hole in the bottom :D I've got too much brewing crap and no 1 system. I have 4 coolers (1 5G, 2 10G[1 with a hole in the bottom] and a 52 Qt) 2 keggles each with 2x 1/2" welded fittings and 1x 1" welded fitting and 2 aluminum turkey fryer pots, 1 in tact and 1 with 2x 1/2" weldless fittings and weldless element and 2 propane burners.
 
If you don't have any luck getting it to seal. Look around some stores and try to find a silicone cookie sheet. Some times you can find them pretty cheap 8-10 bucks then cut some gaskets out of it. The cookie sheets are food grade and rated usually around 350-400 degrees. Used it in my cooler to stop leaking
 
mmurray said:
Just an idea, but most of those molded plastics have a "Mold Release" coating on them, that prevents them from sticking to the molds...

Note: I have no experience trying to stick anything to coolers... but...

Try a fine grit sandpaper and get below the "Non-stick" shinny coating around the area and try again. This should serve 2 purposes, 1. remove the non-stick coating and 2. give a roughened surface for the silicone to stick to. (much on the principle of paint to a smooth surface vs a sanded one)

Hope this helps and good luck!

Cheers,
Mark
Click to expand...

I agree with this explanation. I work with composite technicians, and anything made from a mold has to be treated with release, and it's not removed afterward.
 

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