I need ideas for a material that could be applied to areas of cotton to waterproof it. Either something that goes on wet and dries, or a heat activated material. It must stick permanantly, be flexible, and waterproof.
these guys do exactly what you want.
I bet it is not cheap though…
Luggage guys use a thin pu coating. Don’t know if you can find it in a spray or brush on for individual use. Or you could get another waterproof material like thin pvc backing and use the hemming material to bond the 2 of them, might melt the pvc though, be careful.
what about spraying Scotch Gaurd on the material?
You can use Dupont Teflon, that stuff deflects everything.
does it need to be heat resistant? If so, how high?
There are some high temp EVA hot melt that might do the trick.
It really depends on all of your constraints.
PU is pretty common, but like Skinny said, I haven’t seen it done on a small scale before.
check out outdoor gear shops, they have that kind of stuff. from spray on to application in the washing machine. if it is cotton i would recommend a spray on type (or topical application) if you want to keep the cotton look of the fabric. pu coating, acrylic coating, silicon coating and waterproof laminates have a heavier effect to the fabric. also unless the fabric is some what water repellant, like a nylon or polyester, with coatings (which normally are on the reverse side of the fabric) the cotton will become saturated and the coating/laminate will do the actual repelling of the water.
do a google search for “waterproofing fabric” and you will get a number of products and ideas that you can use.
also check for tent waterproofing treatments. also thompsons water seal has been used in various textile applications, though it may not be as flexible as you would like. tent/outdoor applications are not normally super permanent, they require application, but that depends also on exposure.
even try rubber cement and work it into the fabric.
As for a sustainable option… try Lanolin. It can be applied in a pump-spray bottle to make cotton or other absorbant cloth water resistant, maybe low level water proof if applied liberally. Lanolin is a natural oil taken from sheeps wool.