| Waterproof and moisture-permeable materials are intelligent functional materials that combine the functions of barrier to liquid water penetration and water vapor transportation and conduction.In recent years,due to the outstanding contribution and performance of waterproof and moisture-permeable materials in the fields of textile and apparel,medical and health care,filtration and separation,electronics and electricity,research on waterproof and moisture-permeable materials by scientific scholars and industrial production has been flourishing.Currently,hydrophilic non-porous membrane materials（thermoplastic polyurethane（TPU））and hydrophobic microporous membrane materials（polytetrafluoroethylene（PTFE））dominate the waterproof and breathable materials market.Hydrophilic non-porous membrane materials have stable waterproof performance because there is no pore on the surface of the material,and they rely on water vapor molecule transfer from hydrophilic chain segments to achieve moisture permeability,but the moisture permeability and air permeability are poor.Hydrophobic microporous membrane materials use hydrophobic groups to achieve the effect of liquid water barrier,through the fiber’s internal three-dimensional interoperable pore structure to achieve water vapor transfer,the final material shows satisfactory waterproof and moisture permeability effect,so PTFE hydrophobic microporous membrane materials are popular in the market.However,the traditional process of producing PTFE hydrophobic microporous membrane materials involves toxic substances such as perfluorooctanoic acid,and the final membrane material is less elastic and not easily degradable,so there is an urgent need to design and develop a waterproof and moisture-permeable nanofiber membrane material with excellent elasticity,excellent protection,and environmental friendliness.Electrospinning technology can obtain the layer-by-layer stacked irregular three-dimensional structure of nanofiber membrane materials,the pore size between the fibers is smaller than that of traditional membrane materials,and the porosity between the fibers is higher,the specific surface area of the material is large,and the surface structure is adjustable.However,a large number of toxic solvents are used as spinning solvents（e.g.,tetrahydrofuran,formic acid,N,N-dimethylformamide（DMF）and N,N-dimethylacetamide（DMAc）,etc.）in the electrostatic spinning solution configuration,which have serious negative effects on environmental protection and human health.Therefore,there is an urgent need to develop a green spinning solvent-based electrostatic spinning waterproof and moisture-permeable film material.Above all,this paper is devoted to the development of the green solvent hydrophobic microporous nanofiber membrane material with high elasticity,excellent water,moisture permeability,and protective properties.The mechanism of water and moisture permeability of the green solvent-based nanofiber membrane material is investigated,the mechanism of chemical media penetration prevention of the waterproof and moisture permeable membrane material is revealed,and the mechanism of mechanical resilience of the waterproof and moisture permeable nanofiber membrane material is clarified,and the apparent morphological structure,waterproof,oil and chemical media resistance,moisture permeability and mechanical resilience of the green solvent-based waterproof and moisture permeable nanofiber membrane material are systematically studied.The main researches of this paper are as follows.（1）Using water as the green spinning solvent,and PEO as the spinning template polymer,PTFE/PEO nanofiber membrane materials were obtained by adjusting the mass fraction share between PTFE and PEO.By observing the apparent morphology and pore size distribution of the PTFE/PEO nanofiber membrane material and exploring its mechanical tensile properties and surface hydrophobic properties,the mass fraction ratio of PTFE to PEO was optimized,and finally,when the mass fraction of PEO was 6wt%,the surface morphology of PTFE/PEO nanofiber membrane had continuous and uniform fibers,and the beading and bead structure in nanofibers disappeared,and its fracture The elongation and fracture strength can reach 325%and 0.6MPa,respectively,and the surface water contact angle of the nanofiber membrane can reach 100°.（2）The decomposition temperature of PEO and the melting and decomposition temperature of PTFE were obtained by differential scanning calorimetry（DSC）and thermogravimetric analysis（TGA）,and the high-temperature calcination temperature range of PTFE/PEO nanofiber membrane was determined,and the PTFE nanofiber membrane material was successfully prepared.The decomposition of PEO during high-temperature calcination was confirmed by FTIR and EDS analysis.The results of the mechanical tensile test and water-oil contact angle test of PTFE nanofiber films were used to optimize its high-temperature calcination temperature.According to the results,the PTFE nanofiber film has excellent tensile breaking strength（15.8MPa）and tensile breaking elongation（557.1%）at the high-temperature calcination temperature of 400°C,exhibits superhydrophobicity（WCA=153.9°）and excellent oleophobicity（OCA=128°）.And the relationship mechanism between the crystallinity of nanofiber film and mechanical properties before and after high-temperature sintering was constructed by XRD test.（3）Subsequently,the green solvent-based PTFE nanofiber membrane material was prepared using the optimal process parameters.The nanofiber membrane has high porosity（81.04%）and excellent water（81.50k Pa）and moisture permeability(11.90kg m-2 d-1)properties.The dynamic thermo-mechanical analyzer（DMA）was used to perform the thermo-mechanical analysis of the green solvent-based PTFE nanofiber membrane material,and the results showed that the PTFE nanofiber membrane exhibited stable mechanical properties at different temperatures and had excellent characteristics of high-temperature resistance.In addition,PTFE nanofiber membranes showed excellent resistance to chemical media,with minimal mass loss of 0.14%,0.14%,and 0.17%after 240h immersion in concentrated sulfuric acid,concentrated sodium hydroxide and ethyl acetate solutions,respectively,and the nanofiber membranes maintained excellent hydrophobic and mechanical properties after immersion.The chemical reagent permeation experiments showed that the permeation resistance of PTFE nanofiber membrane to ethyl acetate reached the permeation equilibrium at 5min,and the cumulative equilibrium permeation amount was 0.98μg cm-2;the permeation resistance to methanol reached the permeation equilibrium at 25min,and the cumulative equilibrium permeation amount was 2.79μg cm-2.Therefore,the PTFE nanofiber membrane prepared in this experiment has good double sparse performance as well as chemical media resistance is a green solvent-based nanofiber membrane material with excellent mechanical properties,exhibiting good chemical media resistance behavior and outstanding comprehensive performance for waterproof and moisture permeability applications. |
