I am an undergrad student working on a personal research project involving aeronautics. For the purposes of my project I have found that I need a fabric with a specific strength (tensile strength over density) of greater than 130 kNm/kg which is can be made air-tight. Kevlar, Zylon and Spectra fibers are among the few textiles I've found which meet the strength-to-weight requirements. I have seen reference to zylon and spectra being used in parachute and sail materials and I was hoping someone here could give me more information (any and all information would be appreciated) regarding how these materials are made to be completely air-tight and/or what materials need to be added to them to do so. Thanks!