Sealant quandary

[Slowtack]

Anybody know if its safe to use polysulphide or polyurethane sealant on a polypropylene skin fitting below waterline?
Polysulphide is what I would expect to use with underwater skin fittings as it retains elasticity.
However, I know that polysulphide and polyurethane are not compatible with certain plastics eg ABS, PVC, Polycarbonate, acrylic - but I can find nothing about Polypropylene in that regard. I am reluctant to use Sikaflex or similar polyurethane as it is less accommodating to movement once cured than polysulphide and is difficult to disassemble without damage once cured.

Links:
http://blog.dankim.com/2009/04/24/marine-sealants/
http://www.masticmasters.com/polysulfide-VS-polyurethane.html

 

[alteredoutlook]

How about CT1?

according to their product info http://www.ct1ltd.com/phocadownload/new ct1 tech data sheet 18-06-2012 master.pdf
it should be ok

 

[KAL]

How about CT1?

according to their product info http://www.ct1ltd.com/phocadownload/new%20ct1%20tech%20data%20sheet%2018-06-2012%20master.pdf
it should be ok

Yep. You beat me to it. CT1 or one of the same family of sealants would be what I'd use. I keep a tube on board and one at home. It's just amazing stuff.

 

[Slowtack]

Many thanks alteredoutlook. Cant see anything there about polyproylene compatibility. I know that another fairly similar product Tec 7 is definitely not suitable for that particular plastic, not sure about CT1. Have sent them an email.

 

[Slowtack]

Unfortunately, I just found this on their webpage about sticking plastics to metal.............."With there being so many different types of plastic and metal CT1 will take care of them all, except of course polypropylene." Looks like I might have to use silicone if nothing else emerges. The search continues..................

 

[Chalker]

Arbomast BR, Butyl Rubber??

 

[GrahamHR]

Basically, nothing sticks to polypropylene, unless it's been (oxidising) flame or plasma treated beforehand.

 

[KAL]

Unfortunately, I just found this on their webpage about sticking plastics to metal.............."With there being so many different types of plastic and metal CT1 will take care of them all, except of course polypropylene." Looks like I might have to use silicone if nothing else emerges. The search continues..................

Which is the metal bit? Thought you were putting in a skin fitting through a GRP hull...

 

[prv]

Unfortunately, I just found this on their webpage about sticking plastics to metal.............."With there being so many different types of plastic and metal CT1 will take care of them all, except of course polypropylene." Looks like I might have to use silicone if nothing else emerges. The search continues..................

I would think the problem is not that the CT1 damages the polyprop, but that it won't stick to it. Very little does. If you just want it as a bedding compound, perhaps the lack of adhesion wouldn't matter.

Pete

 

[Slowtack]

There is no metal bit, that is just the name of the CT1 page where I found the relevant info sentence about polypropylene on it. Actually the skin fitting is made of glass filled polypropylene to be precise, not sure if the glass fibres make any difference as regards sealant compatibility though. I have also emailed the fitting manufacturer to see what they recommend. . Nothing in their manual about suitable sealant type. The butyl rubber suggestion looks promising. Seems amazing to me that a skin fitting would be made from a material with such limited sealing possibilities.

 

[Slowtack]

To my amazement the product manufacturer informs me that they have been making the fitting from the same material for 28 years but they are not prepared to offer any advice whatsoever as to a suitable sealant! Tells me to get advice from sealant companies, surveyors, boatyards etc. The sales promo literature doesn't say that you need such assistance to install it. Caveat emptor.

 

[Stemar]

Seems to me that the sealant only has to act as a gasket, so the type is irrelevant, as long as it doesn't actually attack anything.

I'd just put a good thick bead round the hole. push the skin fitting in and tighten until the sealant squidges out all round, but leaves a few mm between the fitting & the hull. Let it all go off, then tighten the rest of the way and trip the excess. For a really tidy job, mask the area around the fitting so the excess doesn't stick to the hull.

 

[Slowtack]

Stemar, that is what I propose to do but my repeated efforts to get Echopilo to name any sealant product that is compatible with their own fitting have come to nought.