# Silicone??



## danthemanx07 (Oct 7, 2007)

Picked up a tube of West's marine grade silicone. At $15 a tube this stuff better cure cancer.

Is there any difference between this stuff and something I can get at Lowe's for $3??


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## 1bandit (Jul 17, 2009)

Yes.Wally world usually has the smaller size reasonable.


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## Voodoo Lounge (Sep 28, 2007)

The one at Lowes doesnt say " marine grade"!! I'm sure one of our resident chemists will chime in shortly on the real difference!!


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## angus_cow_doctor (Apr 13, 2009)

not sure about the chemistry stuff, but I have found that adding the word "marine" to anything jacks up the price by 1000 percent.

for example:

If there was a "marine grade hotdog" and the normal hotdog was 1 dollar, the Marine hotdog is 10 dollars....

If there was a "marine paperweight", and normal weight cost 10 dollars, the marine one is 100 dollars.....

I think it is a Ponzi scheme myself!:banghead


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## oceansbreeze (May 1, 2009)

All the boats I have owned all have been trailered, The longest any of them were in the water was for onlyacouple of days, and I had always used the non-marineDow Corning or GE <U>*Clear*</U> Silicon *<U>Rubber</U>*. Haven't read thelabels for many years but way back in the hippie days the clear had higher temperature rating than white, and I believe that was because the whitehad talc. I don't think any of the silicon is for under the water line, IthinkMarine 4200 or 5200 is only recommended.


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## fisheye48 (Sep 28, 2007)

I dont know about the lowes stuff but 5200 is some badddd stuff!!!


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## danthemanx07 (Oct 7, 2007)

For under the water line or when I need adhesive, 4200, or 5200 if it is permanent, is certainly the way to go. I am just talking SEALANT. Like, for putting a bead around the foot of my console to keep water out of there. I dont need to bond the console to the deck, just seal around it.

I was just hoping that someone had an alternative to the ungodly expensive stuff at West.


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## Patriot (Jun 4, 2009)

Marine Grade has biocide in it to prevent mildew formation and some UV inhibitors. Lowes does carry a marine grade silicone that will work for your appication. About double the price of their regular silicone.

Good luck


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## Crayfishtom (Oct 31, 2008)

Use the bathroom silicone as it has the biocide for mold etc. same stuff. Silicone is silicone. Marine may also have uv inhibitors added however, for what you are using it for it will last and if you clean the boat just add a little bleach to the water/soap or just spray the seal with a weak bleach solution. I use this as I'm tired of paying the higher "marine" prices and West is always much higher. Just say a chemist told you so!

Tom


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## sealark (Sep 27, 2007)

I can tell you one thing about NON marine grade dow or GE silicone. Back in the late 60 when I first discoverd silicone I used it to seal an AC unit in the trailer window. It worked perfect so I thought. It worked perfect for about a year then it started to leak. On close examinang it the silicone that at first was solidly contacted to the aluminum was now loose mildewed and leaking. It seems that with time it does absorb some moisture with age and will come loose. I know nothing about the Marine grade but have seen some aquariums held together with somekind of silicone product. If I were to seal anything on my boat it would be with 4200 or 5200.


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## choppedliver (Apr 4, 2009)

Not all silicones are made the same.



When I used to work for an aircraft stator re-manufacturing facility, we had some orange silicone made to hold the vanes in the stator, that was some holy crap stuff. I mean holy crap because that stuff was almost impossible to get off, make you say holy crap when you tried to pull one of those suckers out. almost impossible to break the seal. It smelled just like regular silicone, but was tough as hell.


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## Crayfishtom (Oct 31, 2008)

choppediver, you are right on the made the same. They all(commercial forms) contain the basic siloxane link(_Si_O_Si_)or chain to make polymers then are compounded with other additives for better properties e.g. temperature,adhesion,color,mold additive and UV inhibitors and some are thick polymer solutions(oil),grease and more rigid (rubber)RTV's.

Again, why pay more for something one may get cheaper. However depending on one's application determines what the person need's to buy.

Then you may need a polyurethane type polymer compound. Just trying to answer the questions. I'm an analytical chemist but have had many courses in organic chemistry too and do know about polymers and have worked with all types over my 50 yrs. in High Energy Research.

No offense!

Tom


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## Mullethead (Oct 4, 2007)

<H3>More info than you asked for - but i think that a polysulfide would work best for the appliclation you described. </H3>

(3M 100) <H3>http://www.boatus.com/boattech/casey/35.htm</H3><H3></H3><H3>What Sealant Do You Need?
_by Don Casey_</H3><P style="MARGIN-BOTTOM: 0px">In every Marine Center you will find an array of different sealants and caulks sufficient to make your head spin. With so many choices, how do you know which one you need?<P style="MARGIN-TOP: 0px">
It is not as difficult as you might think. Virtually all modern marine sealants fall into one of just three types, each with specific characteristics that make it the best choice for some jobs and unsuitable for others. Selecting the right sealant is essentially a matter of identifying the materials you are wanting to seal--specifically if any component is plastic--and of determining the likelihood of ever needing to separate these components. 

_If neither component is plastic and if you want to preserve your ability to disassemble the joint, use *polysulfide*._ <P style="MARGIN-BOTTOM: 0px">Polysulfide is the most versatile of marine sealants. It is a synthetic rubber with excellent adhesive characteristics, and you can use it for almost everything. As a bedding compound it allows for movements associated with stress and temperature change, yet maintains the integrity of the seal by gripping tenaciously to both surfaces. It is also an excellent caulking compound since it can be sanded after it cures and it takes paint well. <P style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px">
However, the solvents in polysulfide sealant attack some plastics, causing them to harden and split. Specifically, you must not use polysulfide to bed plastic windshields or plastic portlights--either acrylic (Plexiglas) or polycarbonate (Lexan). Don't use it to bed plastic deck fittings either, including plastic portlight frames. Plastic marine fittings are typically ABS or PVC, and polysulfide will attack both. If you know that the plastic fitting is made of epoxy, nylon, or Delrin, you can safely bed it with polysulfide. Below-the waterline through-hull fittings are in this group, but when there is any doubt, select an <P style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px">alternative sealant. <P style="MARGIN-TOP: 0px">
Polysulfide adheres well to teak (a special primer improves adhesion), and is unaffected by harsh teak cleaners, making it the best choice for bedding teak rails and trim. The black caulking between the planks of a teak deck is invariably polysulfide. For this application, a two-part polysulfide gives the best results. Polysulfide is the slowest curing of the three sealant types, often taking a week or more to reach full cure. Because it will adhere to almost anything, polysulfide has a maddening propensity to get on everything, so neatness is called for in using this sealant. Polysulfide sealants will have polysulfide printed on the package, or sometimes Thiokol--the trademark for the polymer that is the main ingredient of all polysulfide sealants regardless of manufacturer. 

_If you want the two components to be joined together permanently, use *polyurethane*._ <P style="MARGIN-BOTTOM: 0px">Think of polyurethane as an adhesive rather than a sealant. Its grip is so tenacious that its bond should be thought of as permanent. If there seems to be any likelihood that you will need to separate the two parts later, do not use polyurethane to seal them. <P style="MARGIN-TOP: 0px">
Polyurethane is the best sealant for the hull-to-deck joint. It is also a good choice for through-hull fittings and for rubrails and toerails, but not if rails are raw teak because some teak cleaners soften it. Like polysulfide, polyurethane should not be used on most plastics--acrylic, polycarbonate, PVC, or ABS.
The cure time for polyurethane is generally shorter than polysulfide, but still may be up to a week. 

_For bedding plastic components or where insulation is desirable, *silicone* is the default choice._ <P style="MARGIN-BOTTOM: 0px">Calling silicone a sealant is something of a misrepresentation. It is more accurate to characterize it as a gasket material. If you accept silicone's adhesive abilities as temporary, you will find it is the best product for a number of sealing requirements. It is the only one of the marine sealant trio than can be safely used to bed plastic. It is an excellent insulator between dissimilar metals--use it when mounting stainless hardware to an aluminum spar. It is the perfect gasket material between components that must be periodically dismantled--beneath hatch slides, for example. <P style="MARGIN-TOP: 0px">
Silicone retains its resilience for decades and is unaffected by most chemicals, but it should not be used below the waterline. Because it depends upon mechanical compression to maintain its seal, silicone is not a good choice for sealing hardware on a cored deck. Exposed silicone is a magnet for dirt and repels paint, so never fillet with silicone, and don't use it on any surface you plan to paint.
Silicone sealants typically set in a few minutes and reach full cure in less than a day. 

_For an adhesive seal of plastic components, select a *silicone/polyurethane hybrid*._ <P style="MARGIN-BOTTOM: 0px">An adhesive sealant maintains its seal even when stresses pull or pry the bedded components apart. The sealant stretches like the bellows joining the two sides of an accordion. This accordion effect can be especially useful for plastic portlight installations where the portlights are captured between an inner and outer frame. Although silicone has amazing elasticity, its lack of adhesion means any expansion of the space between the frames is likely to cause the seal to fail. <P style="MARGIN-TOP: 0px">
Either polysulfide or polyurethane would provide a more dependable seal, but polysulfide is certain to attack the plastic, and polyurethane prohibits any future disassembly. The answer to this dilemma is a hybrid sealant--part silicone and part polyurethane. Marketed by BoatLife as Life Seal, this mixture promises a longer-lasting seal for portlights and other plastic fittings where compression of the sealant cannot be assured. 

For more information about sealing and bedding, consult _Sailboat Hull & Deck Repair_ by Don Casey.


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