Why will H2O(g) pass through Gore-Tex (pore size 90 m-6) and not nylon (pore 0.45 m-6) even though its smaller

Question

trying to devise a practical using bromine to pass through goretex and not other materials for new gcse science course!

Answer 1

It depends on what you mean by "Gore-Tex" since there are some variations of fabric/laminate structure depending on the intended use, i.e. "Gore-Tex is not a single product. However, the essential component of "Gore-Tex" is an expanded ptfe (Teflon) matrix partly or completely impregnated with a monolithic film of polyurethane. In spite of what the publicity may say, the water transport properties of Gore-Tex have absolutely nothing to do with the ptfe and are entirely governed by the polyurethane. The ptfe is there primarily as a reinforcing agent (and historical reasons). The water transport properties of the polyurethane depend on its chemistry and there is a trade-off between water permeability and strength. The expanded ptfe matrix allows Gore-Tex to use a more water-permeable form of polyurethane than that used by Sympatex, for example.

Water passes through the polyurethane by effectively dissolving in it. It is then a simple diffusion process that drives it from the high water partial pressure inside the garment to the lower water partial pressure outside. In fact, as the polyurethane increases its water content it becomes better at diffusing water so there is an element of "intelligence" that causes the Gore-Tex to work harder the wetter it gets.

So the pore size doesn't actually have much to do with the transmission of water vapour, it is the polyurethane chemistry. As already mentioned, nylon will also absorb water but it is nothing like as permeable as polyurethane.

I'm not sure about passing bromine through Gore-Tex, my instinct it that it will tend to react with the polyurethane turning it yellow.

Answer 2

gore tex is made of the same stuff as teflon sauce pans so it repells everything. including water so the water droplets are reppeled (by the flourine atoms) as they are attracted to each other and reppeled from the gore tex. but the water vapors can get through as they have more energy and are not attracted to the other molecules around it so the single molecule can make it. Nylon dosent have this repleancy so its just a very small sive.

Answer 3

Water DOES pass thru nylon (and other materials) with a 0.45 um pore size. (This size is COMMON for TDS analysis in water, where you filter the water to remove particulates and recover the filtered water.)

You have to overcome things like surface tension and cohesion, but water WILL pass thru, with the aid of a vacuum pump or an aspirator or the like. I do this all the time....

Answer 4

the pores are bigger in the gortex, thus allowing the H2O(g) to pass through, where as the density in nylon won't allow it, even though it seems feesible

Answer 5

if you are wearing gortex you are probably doing so because you are in wet conditions so you are more likely to get wet.