I have been unable to find a clear answer on this and I know there are quite a few bright minds here on BPL so let's give it a try. The questions are quite techie and people may wonder what importance it has, but I just want to know.
I've been wondering about the question what effect the fiber has on moisture absorption and drying times of fabrics.
First example: fabrics used in baselayers. Often it is assumed that cotton is useless for baselayers. But I've found quite a few studies that give another view. Not the nature of the fiber is important but the way the fabric is constructed, how heavy/thick it is, what the pore/capillary volume is. To be used in baselayers, fibers need to be hydrophilic so that moisture can spread over the fabric and can be taken up in the capillaries. So hydrophobiv fibers like polyester or polypropylene need to be rendered somewhat hydrophilic to get good wicking performance. Next to that, there's the question of the the hygroscopic properties of a fiber. Cotton absorbs 10-14% of moisture vapor, wool up to 30%, polyester up to 1%, polypropylene even less. But that's moisture vapour (to get in balance with the surrounding evironment), not water in liquid form. Up to now, I have been unable to get a clear indication whether fibers also absorb liquid water, not just moisture vapor.
So I wonder, if two shirts were being made, both constructed in exactly the same way, same knit, same thickness, .... but one made from polyester and the other from cotton, which one would absorb more (liquid) water? Or would both shirts absorb equal amounts.
I know from studies that if you take two shirts, one cotton and one polyester, and you calculate drying times, both shirts loose exactly the same amount of water in a given unit of time. The fact that cotton shirts take longer to dry, is because it absorbed more moisture than the synthetic shirt. The reason was that the cotton shirt was made from a heavier grade of fabric, was thicker and contained more volume to store water. Again, I know fabricconstruction played a role, but not if it was crucial that the shirt was made of cotton. Would the result have been the same if it was made from polyester.
All the tests I've seen who compare drying times forget to mention that the tested fabrics differ in more than just the fiber.
Again, I repeat my question, if two shirts were being made, both constructed in exactly the same way, same knit, same thickness, .... but one made from polyester and the other from cotton, which one would absorb more (liquid) water?
Second example (more or less the same): soft shell fabrics made from a nylon/spandex combination are moisture hungry while e.g. polyester with mechanical stretch take up much less water. So it is suggested that a fabric takes up water more easily because it is made from nylon and even more when it contains a certain amount of spandex. Again, I have been unable to find clear studies who confirm this. OK, polyester has a moisture regain of 0,4 to 1% nylon has a moisture regain of about 4 to 8%. Spandex has a moisture regain of 1 to 1,5%. So spandex doesn't seem to add much in absorption capacity compared to nylon. Moreover, moisture regain is about absorbing moisture vapour, not liquid water.
If you compare the surface energy (and thus the hydrophylic/hydrophobic character) of nylon 6-6 and polyester, surface tension of nylon is in fact lower than polyester (=PET) so water will spread a tiny bit easier on polyester than on nylon. For spandex I haven't found real values but knowing that spandex is a segmented polyurethane and I've noticed values from polyurethane which are higer (higher than 50 dynes/cm). So I would assume that fabrics with a minute amount of spandex perhaps could mae wetting out more easily (but is the spandex in the yarns directly exposed to water?).
Coming back to my question: would two jackets made in exactly the same way (weave, fabric, thickness, yarn construction, whatever you can think of) but differing in their fiber composition (nylon/spandex vs polyester), would they absorb equal amounts of water when exposed to rain. If not, which one would absorb more and why?
These questions are perhaps of no direct use for people but I just want to know and the information I have is a bit conflicting. so the Richard Nisleys, Roger Caffins and other bright minds, go ahead.