Sealing PU/Sil seam

[John E]

On my bivy, I ended up with a seam that is PU on one side and Sil on the other. Seam grip only adheres to the PU and silicone seam sealer only adheres to the other.  What can I use that would bond to both? Disassembly is not an option. Thanks in advance!

[Roger Caffin]

I am not aware of anything commercial which can do that.
About all I can suggest is that you use either and rub it well into the stitching.

Cheers

[Sam Farrington]

Try using NAPA Flowable Silicone Windshielf and Glass sealer. Assuming you have access to to a NAPA auto parts store or their web site. Be sure to get the clear, not the black stuff.

There have been a gazillion posts here about how well this stuff seals silnylon.
However, I’ve found that it will adhere also to some PU coatings. It would probably not be an effective bonding agent, but if it adheres to the PU, it should work as a sealer if rubbed in, as Roger says. Note that we are having high temps in much of the US now, so you may have to put it into a room with AC to get it to dry.

Still another possibility, when no amount of planning will allow all the exposed seams to be on either PU coated fabric or SIL coated fabric: Just coat seams on the PU coated surfaces with SeamGrip, and on the SIL coated surfaces with your favorite sil sealer. In addition to the NAPA product and the Sil-Net, there is a Sea to Summit Product called Ultra Seam Sil that flows better. But they all cure in the tube eventually, so it makes no sense to stock up on any of them.

Good Luck.

[William Kerber]

I’m not sure what you are asking. If you mis-matched a SIL side with a PU side, you are probably out of luck. Otherwise, use the appropriate sealer on the outside of the seams for that coating.

[Franco Darioli]

As suggested diluted silicone can work IF it soaks into the seams AND if on the fabric you leave a very thin layer so that it won’t peel off.

For that I would use an irrigation syringe (to push it through the seams) and then a cloth impregnated with mineral spirit to wipe the excess off the fabric .

BTW, I had in mind seam sealing not bonding the two.

 

[John E]

Thanks for the replies thus far! Isn’t there some kind of iron on solution if no liquid adhesive can bond?

[Roger Caffin]

Isn’t there some kind of iron on solution if no liquid adhesive can bond?
The problem is one of chemistry. PU is a hydro-carbon polymer, while the silnylon coating is a silicone polymer. What bonds to one does not in general bond to the other. Oh, you might get a shallow degree of almost mechanical bonding between the two (Van de Waals forces), but nothing more.
Liquid, tape, whatever, does not make any difference to the surface chemistry.

Cheers

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