Fabriction Of Amphiphobic Fluorinated Polyurethane Composite Nanofibrous Membranes With Robust Waterproof And Breathable Performances

Waterproof and breathable fabric is a kind of functional fabric with outstanding waterproofness, moisture permeable properties, windproofness and warmth retention properties. In many severe climatic situations, waterproof breathable fabrics have been developed for use in garments to provide protection of the human body from many extreme conditions, such as rain, wind, and harmful agents, and at the same time they should also let the moist vapor be transmitted from the inside to the outside atmosphere, properly. The number of applications for waterproof and breathable fabrics continues to increase, ranging from military and specialized medical uses to outdoor clothing for leisure and sports. Breathable fabrics are available in a large variety, which can be categorized as closely woven fabrics, coating fabrics, laminated fabrics. Whilst the conventional waterproof-breathable fabrics have high water resistance and windproof performance, they cause considerable discomfort to wearers due to the low water vapor permeability. For waterproof-breathable clothing, both the water resistance and the vapor transmission are very important for user comfort. The water resistant fabric with low vapor transmission would build up humidity and sweat under the garment very quickly, possibly causing the hyperthermia. Hence, there is necessity of developing a waterproof-breathable fabric that can block water while exhibiting a certain level of vapor/air permeability.Electrospinning has become widely applied technique to fabricate polymer fibers in diameters of tens of nanometers to micrometers and provide membrane-like nonwoven webs. The advent of novel technique such as electrospinning may raise the level of vapor/air permeability while maintaining the high level of water protection. In principle, the properties of electrospun nanofibrous membranes are highly dependent on the natures of the intrinsic polymers. So polyurethane (PU) is mostly chosen as the starting polymer for the preparation of waterproof breathable membranes owing to a range of desirable properties such as elastomeric, resistant to abrasion, and excellent hydrolytic stability.In this paper, polyurethane fibrous membranes were prepared from different concentrations (4,5.5, and7wt%) by electrospun. The role of compositions of electrospinning solution on the morphology, wettability and mechanical property of PU membranes were discussed. Furthermore, the as-prepared fibrous membranes exhibited high water resistance (5.7kPa), good air permeability (5.9mm/s), water vapor transmittance (7868g/m2·24h), and comparable tensile strength (15.95MPa), but poor waterproof property(5.7kPa). Amphiphobic, microporous poiyurethane composite nanofibrous membranes exhibiting robust waterproof and breathable performances were prepared by the introducing of fluorinated polyurethane (FPU) containing head perfluoroalkane segment. By employing the FPU incorporation, the pristine PU membranes were endowed with the superhydrophobicity with water contact angle of156°and the oleophybicity with oil contact angle of145°. The role of FPU for the tuning of the morphology, surface wettability, waterproof and breathable properties and mechanical property of resultant membranes were discussed, and a plausible two-step break mechanism upon the external stress is proposed. The quantitative fractal dimension analysis using N2adsorption method has confirmed the correlation between the hierarchical roughness and amphiphobicity. Furthermore, the as-prepared membranes exhibited high water resistance (39kPa), good air permeability (8.46mm/s) and water vapor transmittance (9524g/m2-24h), and comparable tensile strength (10MPa). The present work suggests polyurethane fibrous membranes use as promising materials for a variety of potential applications in protective clothing, bioseparation, water purification, tissue engineering and catalyst carriers, etc., and also provided new insight into the design and development of functional membranes through FPU incorporation.In addition, the porosity and mean pore radius of all types of the PU membranes was characterized and analyzed by density method. Value of the porosity is29.58%,35.24%,40.89%and40.69%for NF, FPUNF-1, FPUNF-2and FPUNF-3membranes, the mean pore radius distribution in the range0.4-1.4μm, confirming the maximum air permeability and water vapor transmittance of FPUNF-3.