Hydrophobic Fibrous Membranes with Tunable Porous Structure for Equilibrium of Breathable and Waterproof Performance

Abstract

to water penetrating and permissibility of vapor transmitting. [ 1 ] According to the previous researches, the fascinating properties of breathable and waterproof performance would be mainly come from the porous structure consisted of hydrophobic raw materials. [ 2 ] Therefore, it has developed various methods to fabricate membranes with outstanding breathable and waterproof performance, such as biaxial stretching, [ 3 ] template-based methods, [ 4 ] and phase separation. [ 5 ] Nevertheless, these methods are still subjected to the diffi culty in regulating the porous structure to achieve best equilibrium of breathable and waterproof performance, as well as the complicated fabricating procedure.Recently, electrospinning method that could obtain fi brous membranes with tunable porous structure has been considered as an available strategy for preparing membranes with breathable and waterproof performance. [ 6 ] Consequently, many kinds of electrospun breathable and waterproof membranes have been prepared using various polymers, including poly urethane (PU), [ 7 ] polyvinylidene fl uoride, [ 8 ] polyacrylonitrile, [ 9 ] and polypropylene. [ 10 ] Among these studies, PU has gained the most attention owing to the prominent elasticity and abrasive resistance, which is important for the practical application. [ 11 ] However, on account of the bad hydrophobicity and relative large fi ber diameter, the electrospun PU membranes in the previous studies exhibited either poor breathability (water vapor transmission (WVT) rate ≤5 kg m −2 d −1 ) or inferior waterproofness (hydrostatic pressure ≤10 kPa). [ 7,12 ] Our group has reported a fabrication strategy of waterproof and breathable fi brous membranes by introducing of hydrophobic PU and carbon nanotubes. Benefi ting from the low surface energy property of PU and hierarchical roughness built from carbon nanotubes, the membranes exhibit high WVT rate (9.2 kg m −2 d −1 ) and hydrostatic pressure (108 kPa). [ 13 ] But, carbon nanotubes are hard to be dispersed in polymer solution and easy to aggregate during electrospinning, which would bring about enormous degradation of performance. Therefore, it is remain a serious challenge to develop an effective and facile strategy to fabricate membranes with outstanding breathable and waterproof performance.It is well known that the electrospun membranes are constructed from randomly accumulating of fi bers, which result Breathable and waterproof membranes have great importance in various applications due to their permissibility of vapor transmitting and resistance to water penetrating. Despite the available strategies, it remains a serious challenge to fabricate membranes with best equilibrium of breathable and waterproof performance. Herein, hydrophobic fi brous membranes have been designed and prepared via electrospinning using polyurethane and fl uorinated polyurethane as the raw polymers. By regulating the relative humidity and electrospinning time, fi brous membranes with tunable porous structure have obtained. Signifi cantly...

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