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What is the idea behind a tubeless sealant? It's understood that it forms a viscous thin film that is pushed from the inside out, closing all micro-pores in the rubber and in the tiny gaps between the rubber and the rim.

But do tubeless sealants remain a highly viscous liquid or do they form a thin rubber film?

Obviously whatever bond is formed must be detachable so that it can be ripped or cut the next time the rubber is replaced, but do some kinds of sealant ever solidify, effectively bonding the rubber to the rim by forming a temporary glue?

Update

If the solidification (whether it's polymerization or something else) results from particles speeding as a result of spraying—it cannot result from exposure to (a lot of) air, since the liquid is perpetually swirling inside the tubes surrounded by air—then the (latex?) accumulation will remain on the exterior of the hole, which is not a recipe for a lasting repair, since the exterior is being constantly abraded. This suggests that there must also be some complementary effect happening, perhaps the mechanical squeezing of particles in pores.

Update2

I'm also curious whether they disclose a minimum for our safety. The recipe may well be a trade secret, but they still need to warn us if skin/eye/inhalation exposure poses a health risk.

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The sealant is a suspension of latex particles. When there is an opening (like a puncture, or a pore in the rubber), the liquid is carried away by the air leaking through the opening, causing the latex particles to collide and to clump. That forms a clog that prevents the air from leaking. It is then not the kind of mechanism as a film.

Note that the latex is not dissolved in the liquid, it is already "solid" and spread over a carrier liquid. As time passes, the carrier liquid evaporates: which causes the particles to collide and then to clump.

Also note that the sealant does not bound with the rim, only with the tire.

EDIT: a more scientific explanation can be found in the video below. It is not specific to sealant though, and doesn't explain what happens when sealant is forced through a hole, but I would suppose that it can break the protein membrane and free the latex monomers. Too much pressure in the tire, the sealant goes too fast through the hole, and there's not enough time for the process "breaking the membrane/clumping" to happen (at least at the desired spot).

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    Does the latex actually polymerize? Polymerization is the creation of long chain molecules, and I'm not sure that just being in contact with other latex molecules is sufficient for them to transform this way. I've been under the impression that the latex physically "clumps" but no chemical transformation occurs.
    – R. Chung
    Nov 8, 2021 at 7:15
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    Not knowing the exact formula's, I can only rely on the info I found on internet. Polymerization is the wording used in effettomariposa.eu/blogs/tech-news/… (blog of a sealant manufacturer) and mbr.co.uk/news/how-does-tubeless-sealant-work-373596 (article quoting sealant manufacturer's representatives). But indeed, coagulation is used too.
    – Rеnаud
    Nov 8, 2021 at 7:41
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    Worth noting there are also Latex-free sealants
    – Nate W
    Nov 10, 2021 at 0:11
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    Btw, it may be more accurate to say that the latex particles clump, a bit like platelets clump in the blood.
    – Weiwen Ng
    Nov 17, 2023 at 14:40

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