Another sealant question

[brak]

Gotta rebed more chainplates. I liked 3M 4000 enough but I'd like to go back to my favorite - Sikaflex.

I have a whole lot of Sika 291 and a new tube of Sika 521 UV. I know how 291 works, like it and it seems to do well - but it becomes yellow when exposed to sunlight (and it will be on chainplate seals). 521 is presumably UV protected but I never tried it. I am also not entirely sure if 521 isn't partially silicone - the packaging is not clear on that. Someone decide for me - which should I pick?

[lbdavis]

None of them. 3M 101. It will stay soft and waterproof for years. On top of that, WHEN those chainplates have to be rebeded or replaced, you will be able to get them out.

4200's like bringing a bazooka to a knife fight.

IMHO.

[brak]

3m 4000 is a replacement product for 3m 101 (the latter is presumably being phased out). It is not at all similar to 4200.

[pigslo]

5200!! My favorite. (before all you guys chime in with your trite warnings on how it is permanent, please don't) It happens to be my favorite.
pigslo

[Maine Sail]

Originally Posted by brak

3m 4000 is a replacement product for 3m 101 (the latter is presumably being phased out). It is not at all similar to 4200.

Brak where do you get this info?? Do you just make it up???


3M UV 4000 is a one part polyurethane with UV inhibitors added. It has a elongation before break of 800% and a tensile strength of 300 PSI.

3M 4200 is a one part polyurethane with NO inhibitors added. It has a elongation before break of 900% and a tensile strength of 300 PSI.

3M UV 4000 is basically, spec wise, 4200 with UV inhibitors added which reduces is elongation before break slightly.

3M 101 is a one part POLYSULFIDE! Polysulfides have a natural UV resistance and are the premier product for use in teak decks. Polyurethanes do not do well with UV so UV inhibitors are added. 3M 101 has a tensile strength of 139 PSI and an elongation before break of 416%.


UV 4000 IS NOT a replacement for 3M 101 and 3M 101 is readily available. According to the 3M rep it is also NOT being phased out.

3M UV 4000 is likely 3M's answer to Sikaflex's very successful one part polyurethane UV 295. I'd stay away from 295 though as it's tensile strength is 450%!!! Your hulls fiberglass laminate and gelcoat has a tensile strength of between 400 and 500 PSI..... You don't need that much adhesion...

UV 521 is a polyurethane "hybrid" with UV inhibitors. It has a tensile strength of 160 PSI and elongation at break of greater than 500%. UV 4000 has double the adhesion of 521 (read: not really necessary) and so does 4200. You could also use use Sika 291 (221 PSI) and just suck up the yellowing..

[brak]

Halekai, I read the info on 3m 4000 vs 101 on another message board. Authenticity is certainly not guaranteed and most likely you are correct on this.

I went with Sika 521, as I'd like to avoid yellowing. 521 spec says that it is a "one part silane terminated polymer" - that silane thing is some sort of organic silicone based compount, they really seem to avoid the issue of what kind of polymer it is.

In any case, I certainly liked working with it - it is very easy to apply, stays put, does not have much tendency to smear on everything around (the way a few other sealants are, which I shall not name), easy to clean up with paper towel or cloth and dries pretty darn quickly. All in all, it is about as close to ideal compound in terms of application as they get. How well it will last and protect my chainplates - we'll see, I guess I can report on that in a while if anyone is interested.

[Maine Sail]

Silane / Silicone info... I hope 521 UV does not leave that silicone residue??? Perhaps saying Silane is more PC to the silicone hating crowd than saying silicone??

It sounds like 521 UV is a silicone/polyurethane hybrid..??

Keep us informed to the long term status of 521 UV..

[brak]

halekai - I was worried about the same thing. Previous sealant on the chainplates was actually silicone (well, that and really old polyurethane and a bunch of other junk, but mostly silicone). On the one hand 521 spec says that it should not be applied to silicone. On the other - nothing should be, and I did the best I could cleaning up (it takes me almost 2 hours to clean up one chainplate). I still figured silicone-like substance on silicone should be no worse (and may be, just may be, better?) than regular polyurethane. Anyway, I will definitely keep my eye on this and let you know. I also have one chainplate sealed with 3M 4000 so I have a good basis for comparison.