Free‐Standing Polyurethane Nanofiber/Nets Air Filters for Effective PM Capture

The filtration performance and light transmittance of nanofiber air filters are restricted by their thick fiber diameter, large pore size, and substrate dependence, which can be solved by constructing substrate‐free fibrous membranes with true nanoscale diameters and ultrathin thicknesses, however, it has proven to be extremely challenging. Herein, a roust approach is presented to create free‐standing polyurethane (PU) nanofiber/nets air filters composed of bonded nanofibers and 2D nanonets for particular matter (PM) capture via combining electrospinning/netting technique and facile peel off process from designed substrates. This strategy causes widely distributed Steiner‐tree structured nanonets with diameters of ≈20 nm and bonded scaffold nanofibers to assemble into ultrathin membranes with small pore size, high porosity, and robust mechanical strength on a large scale based on ionic liquid inspiration and surface structure optimization of receiver substrates. As a consequence, the resulting free‐standing PU nanofiber/nets filters exhibit high PM_1–0.5 removal efficiency of >99.00% and PM_2.5–1 removal efficiency of >99.73%, maintaining high light transmittance of ≈70% and low pressure drop of 28 Pa; even achieve >99.97% removal efficiency with ≈40% transmittance for PM_0.3 filtration, and robust purification capacity for real smoke PM_2.5, making them promising high‐efficiency and transparent filtration materials for various filtration and separation applications.     

Mesoporous Silica Thin Membranes with Large Vertical Mesochannels for Nanosize‐Based Separation

Membrane separation technologies are of great interest in industrial processes such as water purification, gas separation, and materials synthesis. However, commercial filtration membranes have broad pore size distributions, leading to poor size cutoff properties. In this work, mesoporous silica thin membranes with uniform and large vertical mesochannels are synthesized via a simple biphase stratification growth method, which possess an intact structure over centimeter size, ultrathin thickness (≤50 nm), high surface areas (up to 1420 m² g^?1), and tunable pore sizes from ≈2.8 to 11.8 nm by adjusting the micelle parameters. The nanofilter devices based on the free‐standing mesoporous silica thin membranes show excellent performances in separating differently sized gold nanoparticles (>91.8%) and proteins (>93.1%) due to the uniform pore channels. This work paves a promising way to develop new membranes with well‐defined pore diameters for highly efficient nanosize‐based separation at the macroscale.     

空气过滤用微纳米聚丙烯腈/皮芯型聚乙烯-聚丙烯双组分纤维多层复合材料的制备与性能

采用静电纺丝技术将聚丙烯腈(PAN)纳米纤维收集在皮芯型聚乙烯-聚丙烯(PE-PP)双组分微米纤维网上,制备PAN/PE-PP单层复合纤维网,再将多个单层复合纤维网层层堆叠,经热黏合加固,制备PAN/PE-PP多层复合空气过滤材料,研究了PAN/PE-PP复合纤维网的层数和纺丝时间对其孔径及过滤性能的影响。结果表明:多层复合的方式可得到与单层复合材料相似的孔径参数,但两种材料的孔道结构不同。在总面密度和总纺丝时间一定时,当PAN/PE-PP复合纤维网的层数大于10层时,PAN/PE-PP多层复合过滤材料的过滤效率和品质因子Q_F均明显大于PAN/PE-PP单层复合过滤材料,阻力略微增大;其中,相较PAN/PE-PP单层复合过滤材料,20层PAN/PE-PP复合过滤材料对≥0.3 μm颗粒的过滤效率提高了33%,阻力增加了5 Pa,Q_F值提高了30%。当总面密度和层数一定时,延长静电纺丝时间≥210 min,20层PAN/PE-PP复合过滤材料对颗粒的过滤效率可提高至90%以上,但阻力也急剧增大,因此静电纺丝时间为210 min的PAN/PE-PP多层复合材料的过滤性能最佳。因此,与相同面密度的PAN/PE-PP单层复合过滤材料相比,PAN/PE-PP多层复合过滤材料的过滤性能明显提高;微纳米纤维多层复合法是制备高效低阻复合空气过滤材料的有效方法。      

制备参数对聚醚砜/非织造布复合膜空气过滤性能的影响

聚醚砜(PES)是一种综合性能优良的聚合物成膜材料,熔喷非织造布具有良好的过滤效能并广泛应用于空气的过滤.聚醚砜/非织造布复合膜是以PES膜材、致孔剂聚乙烯吡络烷酮(PVP)和溶剂N,N-二甲基乙酰胺(DMAc)作为铸膜液并涂覆在熔喷非织造布上,然后转移至凝固浴中成膜.通过控制铸膜液组分的不同比例、凝固浴温度和第一凝固...     

Design and fabrication of imidazolium ion-immobilized electrospun polyurethane membranes with antibacterial activity

By covalently immobilizing imidazolium ion onto molecular chain, functional polyurethane (PU) is fabricated and thus an effective way is initiated to prepare electrospun membranes with antibacterial activity. In the experiment, PUs containing imidazolium ion side group (Bmim-PUs) are synthesized through a two-step polymerization process. It includes prepolymerization of isophorone diisocyanate (IPDI) with polyester glycol and chain extension polymerization using imidazolium-based ionic diol (Bmim-OH). Then, the obtained Bmim-PUs are electrospun into fibrous membranes with a diameter of ~640 nm. After a careful assessment, antibacterial activities of electrospun membranes against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli are clearly exhibited. The antibacterial efficiency of Bmim-PUs on both bacteria species improves by 60% in comparison with PU without imidazolium ion. This research suggests a simple but effective methodology to design and fabricate ultrafine fibrous membrane with significant antibacterial activity. Moreover, the obtained fibrous membranes have widely potential applications in protective textiles, filtration, and biomedical engineering.     

空气过滤用电纺聚偏氟乙烯-聚丙烯腈/熔喷聚丙烯无纺布复合材料的制备及过滤性能

为开发高效低阻的空气过滤材料,采用静电纺丝技术制备了聚偏氟乙烯（PVDF）-聚丙烯腈（PAN）复合纳米纤维,并与聚丙烯熔喷非织造布复合制得高效复合过滤材料,研究了PVDF与PAN的质量比对溶液性质、表面形貌、比表面积、透气性和过滤性能的影响。结果表明,当PVDF与PAN质量比为3:5时,其溶液可纺性最好,所得纤维直径均匀,约为0.59 μm;利用BET比表面积分析仪测试可得其比表面积约为PVDF与PAN质量比为2:1时的两倍;利用滤料测试仪对PVDF-PAN/熔喷聚丙烯（PP）无纺布复合滤材的过滤性能进行测试,结果表明,静电纺PVDF-PAN纳米纤维层可显著提高聚丙烯熔喷非织造布的过滤性能,PVDF-PAN/熔喷PP无纺布过滤效率可达99.95%,明显高于熔喷无纺布的过滤效率（65%）,过滤阻力为77 mmH₂O（1 mmH₂O=9.8 Pa）,过滤品质因子达0.0987,远高于熔喷无纺布的过滤品质因子0.0168,过滤效果得到显著提升。      

静电纺聚乳酸纳米纤维复合滤料的过滤性能研究

将聚乳酸颗粒加入到质量比为8:2的三氯甲烷与N-N-二甲基甲酰胺的混合溶剂中,室温下配置质量分数为10%的纺丝液,采用静电纺丝法制备了平均直径在620nm左右的聚乳酸纤维。以聚乳酸熔喷非织造布为基布,通过控制纺丝时间的不同得到了负载不同厚度纳米纤维层的可生物降解的复合过滤材料。通过对各试样的孔隙率、孔径及孔径分布、过滤效率的测试发现:随着纺丝时间的增加,复合材料孔隙率不断下降,孔径不断减小,纺丝3h时,孔径基本减小到原先的一半,且分布相对集中,大大地提高了普通过滤材料的过滤效率。     

Effect of fiber orientation in gelled poly(vinylidene fluoride) electrospun membranes for Li-ion battery applications

Battery separators based on electrospun membranes of poly(vinylidene fluoride) (PVDF) have been prepared in order to study the effect of fiber alignment on the performance and characteristics of the membrane. The prepared membranes show an average fiber diameter of ~272 nm and a degree of porosity of ~87 %. The gel polymer electrolytes are prepared by soaking the membranes in the electrolyte solution. The alignment of the fibers improves the mechanical properties for the electrospun membranes. Further, the microstructure of the membrane also plays an important role in the ionic conductivity, being higher for the random electrospun membrane due to the lower tortuosity value. Independently of the microstructure, both membranes show good electrochemical stability up to 5.0 V versus Li/Li⁺. These results show that electrospun membranes based on PVDF are appropriate for battery separators in lithium-ion battery applications, the random membranes showing a better overall performance.     

Synthesis and characterization of magnetically active carbon nanofiber/iron oxide composites with hierarchical pore structures

Polyacrylonitrile (PAN) solution containing the iron oxide precursor iron (III) acetylacetonate (AAI) was electrospun and thermally treated to produce electrically conducting, magnetic carbon nanofiber mats with hierarchical pore structures. The morphology and material properties of the resulting multifunctional nanofiber mats including the surface area and the electric and magnetic properties were examined using various characterization techniques. Scanning electron microscopy images show that uniform fibers were produced with a fiber diameter of ～600?nm, and this uniform fiber morphology is maintained after graphitization with a fiber diameter of ～330?nm. X-ray diffraction (XRD) and Raman studies reveal that both graphite and Fe(3)O(4) crystals are formed after thermal treatment, and graphitization can be enhanced by the presence of iron. A combination of XRD and transmission electron microscopy experiments reveals the formation of pores with graphitic nanoparticles in the walls as well as the formation of magnetite nanoparticles distributed throughout the fibers. Physisorption experiments show that the multifunctional fiber mats exhibit a high surface area (200-400?m(2)?g(-1)) and their pore size is dependent on the amount of iron added and graphitization conditions. Finally, we have demonstrated that the fibers are electrically conducting as well as magnetically active.     

Hydro‐Assisted Self‐Regenerating Brominated N‐Alkylated Thiophene Diketopyrrolopyrrole Dye Nanofibers—A Sustainable Synthesis Route for Renewable Air Filter Materials

With rising global concerns over the alarming levels of particulate pollution, a sustainable air quality management is the need of the hour. Air filtration research has gained momentum in recent years. However, the research perspective is still blinkered toward formulating new fiber systems for the energy‐intensive electrospinning process to fabricate high quality factor air filters. A holistic approach on sustainable air filtration models is still lacking. The air filter model presented in this work uses a simple process involving water‐induced self‐organization and self‐regeneration of nanofibers, and an easy recycling route after the filter life that not only facilitates reuse of the microfibrous scaffold holding the nanofibers but also allows renewal of nanofibers. Three generations of air filters are fabricated and tested, all having high particulate matter (PM)‐adsorbing tendency, high filtration efficiency (>95%), and high Young's modulus (≈5 GPa). The renewable air filters offer a sustainable alternative to the present cost‐intensive electrospun air filters.     

PVA纳米丝基夹心净化材料的结构与过滤性能

研究了纤维面密度不同的夹心材料对不同浊度的聚苯乙烯(PS)微球悬浮液的过滤效率、压力降的变化情况。研究发现,纤维密度为2.5 g/m2时夹心材料的滤性能相对较好,浊度为80NTU时,QF最大为1.713×10-3。通过扫描电镜(SEM)表征了夹心材料的形貌及不同面密度纤维的孔径大小,平均孔径随着面密度的增加而逐渐减小,且过滤效率随着平均孔径的减小而逐渐增加。夹心材料在循环使用5次后,过滤效率及纤维的保留率都下降。     

A Controlled Design of Ripple‐Like Polyamide‐6 Nanofiber/Nets Membrane for High‐Efficiency Air Filter

The filtration capacity of fibrous media for airborne particles is restricted by their thick diameter, low porosity, and limited frontal area. The ability to solve this problem would have broad technological implications for various air filtration applications; despite many past efforts, it remains a great challenge to achieve. Herein, a facile and scalable strategy to fabricate the ripple‐like polyamide‐6 nanofiber/nets (PA‐6 NF/N) air filter via combining electrospinning/netting technique with receiving substrate design is demonstrated. This proposed approach allows the scaffold filaments to orderly embed into 2D PA‐6 nanonets layer with Steiner‐tree structures and nanoscale diameter of ≈20 nm, resulting in the ripple‐like membrane with extremely small pore size, highly porous structure, and hugely extended frontal surface, by facilely adjusting its pleat span and pleat pitch. These unique structural advantages enable the ripple‐like PA‐6 NF/N filter to filtrate the ultrafine particles with high removal efficiency of 99.996%, low air resistance of 95 Pa, and robust quality factor of >0.11 Pa^?1; using its superlight weight of 0.9 g m^?2 and physical sieving manner. This approach has the potentialities to give rise to a novel generation of filter media displaying enhanced filtration capacity for various applications thanks to their nanoscale features and designed macrostructures.     

The effects of carbonization time on the properties and structure of PAN-based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen and activated with carbon dioxide. The effects of carbonization time of PAN hollow fiber precursor on the microstructure, specific surface, pore-size distribution and adsorption properties of PAN-based carbon hollow fiber (PAN-CHF) and PAN-based activated carbon hollow fiber (PAN-ACHF) were studied in this work. After the activation process, the surface area of the PAN-ACHF increased very remarkably, reaches 506 m²g^{– 1}, when fibers are carbonized at 900C for 70 min and activated at 800C for 40 min. The different adsorption ratios to two adsorbates including creatinine and VB₁₂ reflect the number of micropores and mesopores in PAN-ACHF. The dominant pore sizes of mesopores in PAN-ACHF range from 2 to 5 nm     

掺杂无机纳米粒子的阿魏酸分子印迹复合膜的制备

分子印迹膜是一种兼具分子印迹技术与膜分离技术双重优点的新兴技术,但由于有机膜的力学强度较小,在分离过程中容易使印迹孔穴的空间变形和互补官能团位置的失稳,使得其分离效率大大降低。文中使用紫外光引发原位聚合的方法,以聚偏氟乙烯(PVDF)作为支撑膜,将无机纳米材料和铸膜液共混制备了含有无机纳米材料的阿魏酸分子印迹复合膜。利用红外光谱和扫描电镜测试了膜的结构和表面形貌,发现纳米粒子是以纯物理方式共混的,且都分散在孔的周围,有利于维持膜的孔穴结构。通过平板超滤装置对改性膜的分离性能、水通量和承压能力进行了研究,结果表明,添加质量分数0.5%18 nm TiO_2的改性膜性能最好,承压能力在0.4 MPa以上,分离因子在3.4左右,水通量为6696 L/(m~2·h)。     

Influence of graphene oxide sheets on the pore structure and filtration performance of a novel graphene oxide/silica/polyacrylonitrile mixed matrix membrane

The novel graphene oxide (GO)/silica (SiO₂)/polyacrylonitrile (PAN) mixed matrix membranes (MMMs) with high filtration flux and excellent antifouling performance were designed and fabricated in situ by the method of non-solvent induced phase separation (NIPS) from the precursor of PAN hybridized with GO, tetraethoxysilane and 3-aminopropyltriethoxysilane. The influences of GO sheets on the pore and chemical structure, hydrophilic nature and filtration performance of derived GO/SiO₂/PAN MMMs were investigated by the scanning electron microscopy, field emission scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray, Fourier transform infrared spectrometer, pure water contact angles and filtration performance. Results indicated that in situ incorporation of GO sheets and SiO₂ molecules into PAN matrix via NIPS reconstructs the porous structure of derived GO/SiO₂/PAN MMMs with the upright finger-like holes, porous bottom, thinner top layer and high porosity. The spontaneous surface migration or segregation of hydrophilic GO sheets and SiO₂ molecules as well as their synergistic interaction occurred during NIPS greatly ameliorate the top surface structure and property of derived membranes with smoother surface, uniform pore structure and good hydrophilicity. The derived GO/SiO₂/PAN MMMs exhibit a high water filtration flux of 387 L m^?2 h^?1 with the bull serum albumin rejection rate up to 99% and significant enhancement of antifouling performance.     

电纺制备聚丙烯腈/聚偏氟乙烯复合纤维膜及其空气过滤性能

以聚偏氟乙烯(PVDF)为芯层,聚丙烯腈(PAN)为皮层,通过同轴法静电纺丝技术制备PAN/PVDF纳米复合纤维膜。通过向纤维膜的皮层中加入纳米硅粉、气相白炭黑、硅溶胶三种不同的纳米粒子和改变皮芯层溶液挤出速度对PAN/PVDF纳米纤维膜进行结构优化。同时,采用BET、SEM、水接触角、纤维强度仪等对纤维膜的孔结构参数、表面形貌、亲水性、力学性能等进行研究。结果表明:在皮层中加入硅溶胶后的溶液导电能力达到32.90 μL/cm,PAN/PVDF纤维膜力学性能最好,纵向断裂强度达到13.02 MPa。含有硅溶胶的口罩布的品质因子达到0.0236,远大于纯聚丙烯(PP)无纺布的品质因子(0.0127),过滤性显著提高。      

中空纤维担载Al2O3-SiO2复合膜的研制

采用溶胶-凝胶法在α-Al2O3中空纤维载体上制备了Al2O3-SiO2复合膜,并对复合膜的制备条件及稳定性进行了研究.利用SEM和EDS对复合膜的微观形貌及化学组成进行了分析.结果表明,所制备的担载复合膜表面完整、无缺陷.气体渗透实验进一步说明,复合膜具有一定的气体选择性,在0.1 MPa下对H2/N2的分离因子为3.03,表明气体通过膜的扩散以Knuen扩散传质为主.用等温氮气吸附实验测定了非担载膜的孔径大小和分布,其比表面积为294.85 m2/g,总孔容为0.28 mL/g,最可几孔径小于3 nm.     

中空纤维担载Al_2O_3-SiO_2复合膜的研制

采用溶胶-凝胶法在α-Al2O3中空纤维载体上制备了Al2O3-SiO2复合膜,并对复合膜的制备条件及稳定性进行了研究.利用SEM和EDS对复合膜的微观形貌及化学组成进行了分析.结果表明,所制备的担载复合膜表面完整、无缺陷.气体渗透实验进一步说明,复合膜具有一定的气体选择性,在0.1 MPa下对H2/N2的分离因子为3.03,表明气体通过膜的扩散以Knuen扩散传质为主.用等温氮气吸附实验测定了非担载膜的孔径大小和分布,其比表面积为294.85 m2/g,总孔容为0.28 mL/g,最可几孔径小于3 nm.     

PAN/插层高岭石复合材料制备及静电纺丝性能

以二甲基亚砜为前驱体制备插层高岭石(K-DMSO),通过原位聚合制备聚丙烯腈(PAN)与K-DMSO的复合物,利用静电纺丝技术制备PAN/K-DMSO复合纤维膜。采用XRD,FTIR,TEM和TGA研究PAN/K-DMSO复合物的微观形态和热性能,并采用SEM,POM和拉伸试验机对其纤维膜的形貌和拉伸强度进行测试表征。结果表明:PAN/KDMSO中含有高岭石的内外羟基峰,表征层间距的d001值随PAN进入高岭石的层间而增大,部分高岭石被剥离形成厚度为2~5nm的片层结构分散在PAN基体中。K-DMSO的加入使PAN的耐热性提高,PAN纤维膜的直径减小,拉伸强度增加。PAN与K-DMSO的质量比为8∶1时,PAN/K-DMSO纤维膜的拉伸强度与PAN相比,在未处理,冷压和热处理的情况下分别提高了0.92,1.73MPa和1.96MPa。     

Conformation‐Controlled Molecular Sieving Effects for Membrane‐Based Propylene/Propane Separation

Membrane‐based separation is poised to reduce the operation cost of propylene/propane separation; however, identifying a suitable molecular sieve for membrane development is still an ongoing challenge. Here, the successful identification and use of a metal–organic framework (MOF) material as fillers, namely, the Zr‐fum‐ fcu ‐MOF possessing an optimal contracted triangular pore‐aperture driving the efficient diffusive separation of propylene from propane in mixed‐matrix membranes are reported. It is demonstrated that the fabricated hybrid membranes display a high propylene/propane separation performance, far beyond the current trade‐off limit of polymer membranes with excellent properties under industrial conditions. Most importantly, the mechanism behind the exceptional high propylene/propane selectivity is delineated by exploring theoretically the efficiency of sieving of different conformers of propane through the hypothesized triangular rigid pore‐aperture of Zr‐fum‐ fcu ‐MOF.