3m 4200

[ebb]

Got some of this to bed in a plastic (Marelon) thruhull.
It is a
"one part general purpose PU that chemically.... with good adhesion to wood, fiberglass. gelcoat, CERTAIN PLASTICS and metal."

OK, so it says do a test on the certain plastic befor using it.
It says on the tube that

once you open the tube the contents will harden even if you immediately put the top back on.
That's what the label says. It is a clue that 4200 is a polyether 'next generation' urethane that requires very little moisture to set it off. If it is it has no recognized carcinogenic agent in its formula. One could assume that it's ok with potable water.....


I go to endless sites that sell or talk about 3M4200. They All endlessly repeat the above quote and the rest of the product description. Jamestown, WM, Defender. Nobody knows, nobody cares.

Not on a single website - including all the 3M sites - could I find what certain plastics the 4200 was good for and what wasn't.
NOT ONE SOURCE. We do know than generally Polyurethane sealant is no good for ABS and Lexan and for gluing certain plastics to fiberglass. CERTAIN PLASTICS.......S-H-H-E-E-E-S-S-S-S. All the forums bought the hype, nobody was interested.

How is the "test" done?
Does the rubber immediately dissolve the plastic it is not supposed to be used on?
If it isn't going to adhere, do I wait a week for it to cure?
If I'm bedding a fitting, what exactly does the test require, a fire hose aimed at it after installation?
How do I test a goop befor I test it in use?

Why do I have to do the testing?


What's the big secret....? What is so weird about 3M naming what plastics 4200 can be used on and what not? It's patronizing and stupid. And how much time have I spent trying to find out if it's ok to use this sealant on this plastic fitting. It's a potable watertank so I won't use polysulfide which outgasses can't remember what right now. Probably flatulant formaldethane

[bill@ariel231]

interesting stuff. it does set up pretty fast, i've used it topside bedding the fairleads to the cabinsides and below on one of my marelon thruhulls. neither the topside paint, the fairleads nor the thruhull have disolved. I can't say if it's non-toxic as I haven't bitten one...:D

[Tim Mertinooke]

I used it to rebed all of the deck hardware on my former Typhoon and it worked well. Its adhesion properties are pretty strong though. When I added another cleat, I had to move one that I had already glued to the deck using the stuff and when I removed the cleat I wasn;t as careful as I should have been and popped of a small chip of gelcoat. Good stuff. As far as taste we are going to see if Mikey will eat first... (http://www.youtube.com/watch?v=vYEXzx-TINc) Well Mike, what's the verdict?

[Scott Galloway]

Ebb,

It is my understanding that polyurethane and polysulfide when used to bed plastics such as acrylic (Plexiglas), polycarbonate (Lexan), PVC or ABS will cause them to harden, become brittle and inflexible, and to crack or split. So don't bed your cabin ports with polyurethane or with polysulfide for that matter. The fact that you don’t see the plastic melt away when you apply a small amount on some plastic has no bearing on the safety of using these products on plastics. The effect will be realized later.

See Don Casey on this subject in his "Sailboat Hull and Deck Repair" and probably a number of other general sources related to using bedding compounds and marine adhesives. The effect on plastics has to do with a solvent present in polysulfides and polyurethane bedding compounds and adhesives, and is not specific to 3M 4200, or so I understand from my reading on this subject.

Mr. Casey advises on Page 8 of the above referenced book that any “plastic made of epoxy, nylon, or Delrin - such as quality plastic through hull fittings - may be safely bedded with polysulfides.” When he later discusses polyurethane, he does not repeat this statement.

But since you are talking about through hulls here, it would be wise to speak to the manufacturer of the through hull to insure that the product that you are using to bed the through hull is safe and appropriate to use and does not void the product warranty. My motto is play safe, install bronze.

As to using this stuff in potable water tanks or plumbing systems, I wouldn’t, but you really should ask the manufacturer of the adhesive compound about this. Personally since I first saw a health warning on leaded crystal wine glasses, I have been drinking straight out of the bottle. :)

[ebb]

Hey Scott,
well that's it, isn't it...? Obviously no synthetic rubber sold in the marine store should be used on any plastic.
Except 'certain plastics'.

My rant is that
3M should print on the label WHAT CERTAIN PLASTICS 3M4200 can be used on.
YES....?

Why should I have to go to Don Casey (have to buy his book) for information?
His info, while no doubt well researched, is GENERAL, non-specific, and OUT DATED. Is Don Casey an expert?


I'm pretty sure that 3M's coyness has much to do with lawsuits and liability. Lie ability? As I suggest, any google informed skipper can find the common name or brand name of a plastic if the generic chemical name is given. No fooling around; 'This product should not be used on polyvinyl chloride pipe' - or what ever!

'This product can be used to bed-in metal fittings on polyester, although it may cause stress cracking in gelcoat in extreme conditions (temperatures over 100 degrees.)'


I did come upon a Spec Sheet from 2000 on 3M4000 and 3M4200 that stated the product COULD be used on (ALL) plastics. Unspecified. I can find no spec on current 3M4200 2007.
"Remember Sir, you should have no complaint, we did warn you right on our product label that 4200 could be used on certain plastics and metals."


Primary interest in a caulk/sealant/adhesive is: Will it work in my application.
Will it stick. How long will it last.
Secondary interest in a caulk is: How toxic is the material
A) toxicity during application.
B) toxicity in the environment (like the interior of the boat)
Thiokol/Polysulfide is said to 'outgas'. But I have not seen a clear explanation of this - nor just what is out gassing?
Polyurethane like 3M4200 has no solvents in it. One assumes it does not outgas.
It is also not clear if a synthetic rubber once it has set up is non-toxic or inert - as it is sometimes said of the catalytic chemicals we use around the boat.
If you are going to close up your cabin on a cold winter's night, it may not only be your heater that might kill you, but, obviously, all the other stuff you put the boat together with.
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I bought a blisterpack tube of 3M4200FC from WM
in order to caulk in two thruhulls in two epoxy water tanks.
The amount of rubber exposed to the potable tank water is a 1/16" bead around a 1 1/2" flange. Not much exposure there. There is the efficacy of using epoxy as a potable water storage tank, but that is another story. No one can convince me that drinking water from a metal tank is any safer. Or even soft plastic bottles.

The goop in the tube was hardly squeezable. Just hanging around the store it's getting hard!

This made it easy to apply to the work. Neater, no long snotty threads of rubber. I used an acid brush with bristle cut to about 1/4".
At one point I used a small block of wood to lean on the tube as my fingers wouldn't squeeze the toothpaste tube hard enough to get it out. It promptly blew out the bottom! Can't win.

I agree with you that no synthetic rubber should be used for drinking water connections... but some of us use the 'mea culpa exemption' to be safe.