hybrid silicone/polyurethane
Life Seal by Boat Life. A bit confusing. Life Calk is the p.sulfide. That's Life.
The hybrid mix has the attributes of both but without silicone's nasty oily gelcoat contaminating quality. The gelcoat contamination of silicone means that nothing, no caulk, will ever stick in that place again - not even silicone. I have had to remove the gelcoat in places on 338.
It does not appear that silicone contaminates, in this way, when combined with polyurethane.
While we were out to lunch, hybrid caulks have progressed somewhat. We now have specific choices coming from Bostik. My understanding is that while we've had the one Boat Life product, Bostik has expanded the hybrid line in construction, industry, and marine for more than a decade in Japan and Europe. Successfully. We no longer have to depend on the restricted uses of polysulfide caulk or polyurethane caulk - BOTH OF WHICH HAVE REALLY LIMITED USE ON A BOAT. Neither can be depended on to stay elastic or flexible on deck for long (5 to 7 years springs to mind) - which is what the newer hybrids promise to fix - at least twice the life on deck of p.sulfide & p.urethane. With silicone caulk having NO USE ON A BOAT.*
I have not yet used these Bostik products (There are four listed at the address below - but there are more Bostik SMP, silyl-modified-polymer, products - some of which have revolutionized wood (and cork) deck applications.
Bostik 70-08A is a low slump, high green strength bedding for windows, windscreens, glass, p.acrylate, p.carbonate, hatches, portholes, cleats, fittings. Directed toward glazing situations. More of a paste, less compressible.
It is permanent, elastic, UV resistant, sandable, paintable. Can be tooled with soapywater or alcohol. User friendly, that's what they say.
Bostik Marine 940A (the slow version with 30/45 min open time)
will give us permanent elastic bonds, the same UV resistance, and it sticks all metals, fiberglass, epdm rubber, pvc. No primer needed. Both caulks produce No outgassing, No isocynates, No organic solvents. B.M. 960SR will not 'pull gelcoat'. It may be comparable with 3M4200 in that regard - except it is a silyl-polymer hybrid. BM940A may be compared with 3M5200. This is my take.
While these second two caulks seem to be the solution for nearly EVERY caulking situation on a boat, the data sheet says it is not for glazing.
google Bostik - Marine Sealants and Adhesives
www.bostik-us.com/products/index.asp?fa=categories&divisionld=11&categoryld=4 7
[if you get main site: curser 'Marine' on menu. Then curser SMP. Data sheets here.]
Use the primer (MSR Primer M) for high stress wet conditions. While the data sheet states no primer is necessary, it does say the primer will enhance adhesion and bond.
Imco, along with a chainplate upgrade, it ought to be included. Could possibly help where damn silicone caulk has gone before.
By the way, Bostik has been in the US since 1892. You can get the stuff through JamestownDist.
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This comment here is a later addition:
Jamestown Dist Online lists only the usual array of caulks.
THEY ARE NOT LISTING ANY BOSTIK PRODUCTS.
Finding an internet catalog site for Bostik (also Samson) marine products is totally frustrating. There is no direct source for Silyl Modified Polymer that I am able to find. Torresen is a source but consistently have the highest prices for anything, so I do not visit their site anymore. Other sources are equally useless. For instance, using Bostik's own distributor index for marine caulk brings up local construction contractors. They do not have any marine sealants, And they do not retail to the lumpen sailor.
Haven't a clue why their marine rubbers are not able to be sold in our marine catalog venues. THEIR LOSS.
It means their, what looks like great products, will not enter the mainstream.
Recommendations from the gallery forums would do a lot to spread the word. OUR LOSS as well. I will not pursue this any further.
IT MAY INDICATE BOSTIK PRODUCTS ARE TOO DIFFICULT TO USE.
AND IT MAY ALSO BE AN INDICATION THAT THE PRODUCTS ARE TOO OVERPRICED TO SURVIVE THE COMPETITIVE MARKETPLACE.
VIZ; TO PROTECT THEIR DISTRIBUTORS THEIR CAULKS WILL NOT BE DISCOUNTED IN CATALOGS AND STORES.
To be fair: If you have the hardcopy 1000 page Jamestown Dist Building and Marine Supplies catalog, you will find Bostik 940 and 960 listed for about $16/$17 a tube, Page 405 in their BIGBOOK. They do not seem to know that these two products are hybrid sealants. 1-800-423-0030. Good Luck.
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*Aside from the UV and heat exposure problems that p.sulfide and p.urethane both have, p.urethane cannot be used exposed to kerosene, diesel or gasoline - and many other solvents and cleaners. P.sulfide (OK with fuels) cannot be used with most plastics and exposed to potable water due to out-gassing. To be fair, NO mention on any Bostik data sheet iis given to SMP being OK with fuels. By inference in could be used with potable water as it has no solvents in it. Research needed here.