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I am seam-sealing a tent made from silpoly with silicone sealant (generic 100% silicone, couln't find any silnet around me).

The fabric is very slippery, much more than regular polyester fabric or nylon fabric.

The parts covered in silicone sealant are the opposite of slippery (missing a word here, help?).

Is there any reason for that?

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  • Wouldn't be much of a sealant if it just slid right off would it? – ShemSeger Nov 7 '15 at 1:16
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Silpoly is based on polyester, which means it's hydrophobic (doesn't absorb water). Not all slippery materials are hydrophobic, but this definitely factors in. Silicone sealant also repels water, but through different properties. Those different properties are also the ones that let it adhere to many different surfaces. Silicone has a high coefficient of friction but a low resistance to shear, which is why it works as a lubricant.

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  • I observed the same thing will silnylon, though. Nylon is less hydrophobic that polyester, I think. Since the silicone coats the base fabric, I would have though it would be the main factor of friction. – njzk2 Jan 26 '16 at 14:47
  • @njzk2 It's probably in the way the silicone bonds with nylon and polyester. I'm no chemist or materials engineer, but I've observed substances having different properties dependent on the material they are bonding with. It's possible that the silicone used in each has different properties as well. The silpoly is likely using a silicone-based polymer instead of standard silicone. – David R. Jan 26 '16 at 16:33
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I'm not a materials scientist, so can't give you a definitive answer.

But I do know that if you make your own silnylon or silpoly by soaking the base fabric in a solution of silicone and mineral spirit and air-drying, the final material is far less slippery than commercial silnylon/silpoly.

So it seems that the slippery finish of the commercial materials is an artifact of the manufacturing process used, rather than anything inherent in the silicon itself.

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    could be. thanks for your answer! might be a DWR wax finish. – njzk2 May 7 '16 at 13:33

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