Waterproof and breathable membranes of waterborne fluorinated polyurethane modified electrospun polyacrylonitrile fibers

Creating an efficient and cost-effective approach that can provide advanced microporous membranes with high waterproofness and good breathability has proved to be tremendously challenging. This work responds to these challenges by designing, fabricating and evaluating an electrospun polyacrylonitrile (PAN) fibrous membrane which was modified with waterborne fluorinated polyurethane (WFPU) to achieve high waterproof and breathable performances. By employing the WFPU modification, the pristine PAN fibrous membranes possessed remarkable superhydrophobicity with an advancing water contact angle of 159° as well as adjustable pore structure. Significantly, the waterproofness was confirmed to depend on the maximum pore size and surface wettability, in good agreement with the Young–Laplace equation, and a geometric coefficient A was introduced as a geometric factor to evaluate the torturous pore structure in electrospun fibrous membranes. Furthermore, the resultant membranes could present a high waterproofness up to 83.4 kPa, large water vapor transmission rate over 9.2 kg per m2 per day, good air permeability over 5.9 L m−2 s−1, suggesting them as promising candidates for a variety of potential applications such as protective clothing.