| Functional garment materials with robust waterproofness and breathability have attracted a great deal of attention.Waterproof and breathable functional garment have been developed for the use in fabrics to provide the wearer with a greater level of comfort under many extreme climatic conditions,while still supplying protection of human body from environmental factors,such as rain,wind,and snow.The current waterproof and breathable garment include high-density woven fabric,coated fabric and laminated fabric.High-density woven fabric owe their good breathability and moisture permeability to the thin and smooth yarns that are usually made from microfibers,but the waterproof property is relative poor.The waterproofness of the coated fabric is good due to the non-porous structure,but the moisture permeability is not very well.As one kind of the mainstream products,laminated fabric have more excellent comprehensive waterproofness and breathablity compared to the both formers,which is due to the core layer of the fabric-waterproof and breathable functional membranes.This permeability to water vapor but resistance to water droplets make the functional membranes not only applly in textile and garment industry,but can also be employed in medical and health care,building external wall,aerospace and aquaculture industry.Currently,the commercial waterproof and breathable membranes have two types,such as polytetrafluoroethylene(PTFE)stretching microporous membranes and hydrophilic thermoplastic polyurethane(TPU)nonporous membranes.The major drawbacks of PTFE membranes are the difficulties in recycling and their high price.Actually,there is a negative relationship between the level of protection and comfort properties.These disadvantages restrict the practical application of W & B membranes.Hydrophilic TPU nonporous membranes offer a higher level of protection but lower water vapor permeability which cause some discomfort for the wearer.As a result,it is urgently needed to develop a new technology for alternative membranes which can offer a combination of adequate waterproof performance and comfort satisfaction,simultaneously.Electrospinning,as one versatile technique to produce porous nanofiber membranes,has been of considerable interest within wide range of raw materials,lowpower consumption,and convenience to create hydrophobic surface.Apart from this,the other unique advantages,such as,low weight,small pore size,high porosity,interconnected tortuous channels,and controllable porous structure,which impart an electrospinning strategy to effectively fabricate functional nanofiber membranes.But there are some great challenges during the fabrication of electrospun waterproof and breathable membranes.For example,the hydrostatic pressure and water vapor transmission can not be improved simultaneously,fluoric materials lead to environment contaminate,and excellent hydrophobic and corrosion-resistant membranes can not be prepared.In this paper,innovation strategies combining electrospinning with thermally induced physical bonding and chemical cross-linking were developed.Two main aspect progresses were realized and listed as below:Firstly,macroporous membranes with robust waterproofness,breathability and mechanical properties have attracted a great deal of attention.However,great challenges still remained in developing an effective and cost-efficient method to fabricate such materials.(1)In this study,polyacrylonitrile(PAN)/fluorinated polyurethane(FPU)nanofibrous composite membranes with enhanced waterproof and breathable performance were fabricated by combination of electrospinning and heat post-treatment.The introduction of FPU enriched the nanofibrous membranes with superhydrophobic surface with water contact angle of 151 o,optimized pore size and porosity.Moreover,the relationship among hydrostatic pressure,pore structure and surface wettability has proven to be in accordance with Young-Laplace equation.By employing the heat posttreatment,the pristine PAN/FPU composite membranes were endowed with physically adhesion structure,thereby significantly improved the waterproof-breathable performance as well as the mechanical property.Owing to these effects,the resulting thermal treated PAN/FPU composite membranes exhibited the integrated properties of high hydrostatic pressure(114.6 k Pa),water vapor transmission rate(10.1 kg m-2 d-1)and good tensile strength(9.4 MPa).Furthermore,the reinforced PAN/FPU nanofibrous composite membranes have great potential to be used as functional materials for fabricating separation media,filter,outdoor sportswear,chemical protective clothing,and army combat uniforms.(2)In this study,a new type of fluorinated polyurethane/polyacrylonitrile/polyvinyl butyral nanofibrous membranes(FPU/PAN/PVB NFM)with a blocked isocyanate prepolymer(BIP)as chemical cross-linking agent were fabricated.The composite NFM,with robust mechanical,waterproof and breathable performance,has been prepared using an innovation strategy combining electrospinning with thermally induced physical bonding and chemical cross-linking.By systematically tuning the cross-linked temperature and time as well as the concentration of PVB and BIP,large breaking elongation(81.5%),good hydrostatic pressure(110 k Pa)and modest WVTR(9.6 kg m-2 d-1)of the membranes were achieved.Meanwhile,the physically bonded structure and chemically cross-linked networks between PVB and BIP endowed the composite NFM with the robust tensile strength of 32.8 MPa,which was three times higher than that of pristine FPU/PAN membranes.Considering the excellent performance of the asprepared membranes,this simple and intriguing approach may provide a versatile platform for exploring the applications of the bonded and cross-linked membranes in separation processes,membrane distillation,self-cleaning materials,and protective clothing.Secondly,the demand of water-resistant and breathable materials applied to a separation medium and protective garments is steadily increasing.Typical approaches to obtain these functional materials are based on hydrophobic agents and porous substrates with small fiber diameter,tiny pore,and high porosity.However,a fluorinated hydrophobic finishing agent usually employed in providing effective waterproofness is limited with respect to their environmental persistence and toxic potential.(1)Herein,with the aim to keep a balance between the water-resistance and breathability as well as mechanical properties,we fabricate a novel fluoride-free functional membranes by electrospun polyacrylonitrile(PAN)nanofibers modified with polydimethylsiloxane(PDMS).We fabricate a novel fluoride-free functional membranes by electrospun polyacrylonitrile(PAN)nanofibers modified with polydimethylsiloxane(PDMS).As determined by morphological,DSC,and FT-IR analyses,the curing reaction of PDMS macromolecules formed an abundance of hydrophobic adhesive structures,which improved the waterproof performance dramatically and imparted relative good breathability at the same time.By systematically tuning the curing temperature as well as the concentration of PDMS,the modified PAN membranes with 4 wt% PDMS possessed good water-resistance(80.9 k Pa),modest vapor permeability(12.5 kg m-2 d-1),and air permeability(9.9 mm s-1).Compared with pristine PAN membranes,the modified membranes were endowed with enhanced tensile stress of 15.7 MPa.The good comprehensive performance of the asprepared membranes suggested their potential applications in protective clothing,membrane distillation,self-cleaning materials,and other medical products.Furthermore,the proposed relationship between porous structure and waterproof/breathable property as one considerable principle is applicable to designing functional membranes with different levels of protective and comfortable performance.(2)Superhydrophobic waterproof-breathable membranes have attracted considerable interests owing to their multifunctional applications in self-cleaning,antiicing,anticorrosion,outdoor tents,and protective clothing.Despite the researches pertaining to the construction of superhydrophobic functional membranes by nanoparticle finishing have increased drastically,the disconnected particle component is easy to fall off from the membranes under deformation and wear conditions,which has restricted their wide use in practice.Here,robust superhydrophobic microporous membranes were prepared via a facile and environmentally friendly strategy by dipcoating amino-silicone oil(ASO)onto the electrospun polyacrylonitrile(PAN)membranes,followed by Si O2 nanoparticles(Si O2 NPs)blade coating.Compared with hydrophilic PAN membranes,the modified membranes exhibited superhydrophobic surface with an advancing water contact angle up to 156 o,after introducing ASO as low surface energy substance and Si O2 NPs as filler to reduce the pore size and construct the multi-hierarchical rough structure.Varying the concentrations of ASO and Si O2 NPs systematically,the modified PAN membranes with 1 wt% ASO and 0.1 wt% Si O2 NPs were endowed with good water-resistance(74.3 k Pa),relative low thermal conductivity(0.0028 W m-1 K-1),modest vapor permeability(11.4 kg m-2 d-1)and air permeability(20.5 mm s-1).Besides,the inorganic-organic hybrid coating of ASO/Si O2 NPs could maintain its superhydrophobicity even after 40 abrasion cycles,and were found to resist variations on the p H scale from 0 to 12,and retain their water repellent properties when exposed to harsh acidic and alkali conditions.This facile fabrication of durable fluorine-free superhydrophobic membranes simultaneous with good waterproof-breathable performance provides the advantages for potential applications in self-cleaning materials and versatile protective clothing. |
PDF Full Text Request