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

Abstract

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 m 2 per day, good air permeability over 5.9 L m À2 s À1 , suggesting them as promising candidates for a variety of potential applications such as protective clothing. † Electronic supplementary information (ESI) available: Details synthesis and structure conrmation of WFPU, FE-SEM, stress-strain curves of PAN and WFPU@PAN-8 membranes, pore size distribution and maximum pore size of WFPU@PAN-8 membranes, and Movies S1 and S2. See

Preparation of electrospun polyurethane/hydrophobic silica gel nanofibrous membranes for waterproof and breathable application

“…Figure c presents the O1s spectrum consisting of of three fitted curves with binding energies of 532.3 (CO), 532.9 (CO), and 533.6 eV (SiO). Meanwhile, Si2p curve could be resolved into three component peaks of 102.5 (OSiO), 103.5 (CSi), and 104.2 eV (Si(O) 4 ) , as depicted in Fig. d.…”

Improving waterproof/breathable performance of electrospun poly(vinylidene fluoride) fibrous membranes by thermo‐pressing

“…Among them, surface modification and thermal post‐treatment have been also proposed to improve waterproof/breathable performance . For instance, Wang et al prepared a waterborne fluorinated polyurethane modified electrospun polyacrylonitrile fibrous membrane, which possessed relatively high tensile strength (14.4 MPa), hydrostatic pressure (83.4 kPa), and WVTR (9.2 kg m −2 d −1 ). Sheng et al found that the thermal treated polyacrylonitrile/fluorinated polyurethane nanofibrous membranes with fiber‐fiber bonding structure exhibited the improved tensile strength (from 3.11 to 9.4 MPa), hydrostatic pressure (from 53 to 114.6 kPa) and WVTR (from 8.7 to 10.1 kg m −2 d −1 ) by adjusting heating temperature and time.…”

Waterproof and Breathable Electrospun Nanofibrous Membranes

“…The above‐mentioned doping modifications show limited effect on improving hydrophobicity of extremely hydrophilic nanofibers, such as PAN, polyvinyl alcohol (PVA), and electrospun inorganic nanofibers. In view of this, many researchers have applied surface modification treatment to develop W&B membranes with hydrophobic materials including FPU, fluoroalkylsilane (FAS), polydimethylsiloxane (PDMS), and amino‐silicone oil (ASO) . Combining the virtues of high porosity of nanofibers and hydrophobic property of surface modification layer, this strategy could realize the effective regulation of pore structure and surface wettability of electrospun membranes simultaneously, which is applicable to construct electrospun W&B membranes .…”

“…a) Schematic illustration for fabrication of WFPU@PAN fibrous membranes and θ adv of WFPU@PAN‐8 fibrous membranes modified with WFPU emulsions with various concentrations. Reproduced with permission . Copyright 2014, Royal Society of Chemistry.…”

“…Recently, Wang et al [86] synthesized environmentally friendly waterborne fluorinated polyurethane (WFPU) by accomplishing a self-emulsifying polymerization reaction and immersed PAN nanofibers into the WFPU emulsions (Figure 7a). It should be mentioned that WFPU emulsions filled the voids and then made nanofibers adhere to each other.…”