多级结构静电纺纳米纤维膜在空气过滤领域研究进展

静电纺纳米纤维膜具有纤维直径小、比表面积大、孔隙率高等优势,使其在空气过滤领域具有广阔的应用前景。相比特殊结构的纳米纤维膜,常规的静电纺纤维膜堆积密度大、过滤阻力高,增加了在实际使用中的能源消耗。从静电纺纤维膜结构和过滤性能的角度探讨了高效低阻空气过滤纳米纤维膜的构筑,介绍了珠粒、突起和多孔结构纤维膜在空气过滤领域的研究进展,指出了多级结构静电纺纳米纤维膜是高效低阻空气过滤膜的重点研究方向。     

静电纺丝纳米纤维膜空气过滤研究进展

静电纺丝纳米纤维膜具有高比表面积、孔径小、孔隙率高、纤维均一性好等优点,在空气过滤及个体防护等领域表现出巨大的应用潜力.总结了近年来国内外关于静电纺丝法制备高效低阻和功能化(抗菌、可降解、疏水和耐高温)新型空气过滤材料的最新研究成果,分析和讨论了现有研究中存在的问题,并对未来的发展方向进行了展望.     

光致变色PVA/PEI纳米纤维膜制备及性能

针对传统光致变色纤维膜受酸碱等外界影响易导致变色效率低,以及稳定性不高的问题,提出在传统静电纺丝制备PVA/PEI纳米纤维膜的基础上,负载光致变色纳米微球,然后与戊二醛交联,得到性能稳定的光致变色纤维膜,并考察了PVA/PEI质量比、戊二醛交联以及光致变色纳米微球含量对光致变色纤维膜性能的影响。结果表明：在PVA/PEI的质量比为75∶25,光致变色微球的含量为10%时,经过戊二醛交联的光致变色纤维膜表面光滑,串珠连续且均匀;随着紫外光照的增加,纤维膜的颜色逐步加深,但当光致变色微球的含量大于10%时,颜色不再发生变化;将光致变色纤维膜浸水24h,纤维膜仍保持连续且均匀的多孔纤维结构。根据以上试验看出,纤维膜材料可用于环境领域中,以达到美化环境的目的。     

基于气流雾化静电纺纳米纤维的制备及其空气过滤性能

为克服传统单针头静电纺丝生产效率低的问题,在现有气流辅助静电纺丝的基础上设计一种基于气流雾化静电纺丝装置。以聚丙烯腈(PAN)溶液为纺丝液,采用自主设计的气流雾化静电纺丝装置制备纳米纤维膜,分析了其成形原理和过程以及气流压力、纺丝电压对成形纤维形态和直径的影响,并测试其空气过滤性能。结果表明:当纺丝液的质量分数为12%,纺丝气压为0.2 MPa,纺丝电压为30 kV时,纤维的平均直径均为200 nm左右,产量达5 g/h,其过滤效率高达97.5%,气流雾化静电纺丝为纳米纤维批量化制备提供了新途径。     

磺化聚醚醚酮纳米纤维膜的制备及其吸附性能

通过静电纺丝法制备了不同磺化度的磺化聚醚醚酮(SPEEK)纳米纤维膜,运用扫描电镜、热重分析仪分别对纤维的形貌和热性能进行了分析,并利用紫外-可见分光光度计研究了纤维膜对亚甲基蓝染料的吸附行为。结果表明:随着磺化度的增加,纺丝束流的稳定性得到改善,纤维直径减小;纤维膜对亚甲基蓝具有良好的吸附能力,在p H值=7时其对亚甲基蓝的去除率最大,平衡吸附时间约为90min;热力学分析表明,使用Freundlich模型描述SPEEK纳米纤维膜对亚甲基蓝的吸附行为更加合理;动力学分析表明,SPEEK纳米纤维膜对亚甲基蓝的吸附遵循准二级动力学模型。     

聚乳酸复合空气过滤材料的制备及性能研究

以分子质量为7万的聚乳酸（PIA）为原料,分别用不同的溶剂制得两种纺丝液,并采用静电纺丝法将其分别纺在水刺无纺布和熔喷无纺布上,采用TSI8130仪器对阻力和效率进行测试,比较两者的过滤性能。结果表明：当纳米纤维膜厚度为2mm左右时,水刺非织造布与纳米纤维的复合材料过滤效率从近乎0提高到45．88％,当纳米材料厚度为1mm左右时,提高到26．12％;熔喷非织造布分别与1mm和2mm厚度的纳米纤维膜复合后过滤效率分别提高了23．7％和24．6％,但缺点是过滤阻力提高。     

静电纺纳米纤维复合梯度型空气过滤材料的研究进展

概述了静电纺纳米纤维及其复合梯度过滤材料的特性,详述了国内静电纺纳米纤维复合梯度型空气过滤材料的制备、过滤模型理论及数值模拟等研究进展。基于不同纤维层过滤不同粗细颗粒物,每一层纤维网发挥各自独特作用,可采用多种结构和折叠结构复合,增大过滤面积,制备多层梯度的静电纺纳米纤维复合滤材,使滤材具有高效低阻、容尘量大、使用寿命长等特点,是未来空气滤材的重点研发方向;同时应加强过滤模型设计与数值模拟研究,通过滤材的应用数据不断修正模型,促进滤材性能的改进。     

静电纺抗紫外PVA/芦丁纳米纤维膜的制备及其性能研究

以聚乙烯醇(PVA)为原料,以芦丁为改性剂,将PVA与芦丁共混于去离子水中,通过静电纺丝制备抗紫外PVA/芦丁纳米纤维膜,并对其性能进行表征。结果表明:静电纺丝工艺条件为电压20 k V,纺丝速度0.5 m L/h,接收距离10 cm,温度30℃;加入少量芦丁,对PVA静电纺丝成纤性无影响,但纤维直径增大,直径均匀性变差;纤维中PVA与芦丁之间存在氢键;相对PVA,芦丁质量分数为4.76%时,PVA/芦丁纳米纤维膜的纤维平均直径为302 nm,抗紫外系数大于40,具有良好的抗紫外性能。     

基于静电纺丝技术PAN基碳纳米纤维膜性能及应用研究进展

主要介绍了近年来国内外研究学者利用静电纺制备聚丙烯腈(PAN)基碳纳米纤维膜工艺过程,主要包括纳米纤维膜的制备、预氧化和炭化等工序.另外,还综述了PAN基碳纳米纤维膜的性能优化方法及其应用进展.     

水过滤用膜材料的制备及其性能研究进展

根据过滤分离用水处理膜的制备工艺的不同,重点介绍了三种形式的膜:平板膜、中空纤维膜以及静电纺纤维膜。平板膜因为制备工艺简单、操作便捷,最易于进行功能化改性,因此属于研究最为广泛的一种水处理膜,但是由于受到平板膜内部孔隙率及孔结构的影响,其较小的过滤通量又在一定程度上限制了其应用。中空纤维膜的孔结构特点类似于平板膜,但是其易于集成及器件化的特点,使其成为目前工业用膜的主要形式之一。静电纺纤维膜的产业化应用还处于初级阶段,然而静电纺丝技术是一种制备直径为微米至纳米级超细纤维的重要方法,静电纺纤维膜比表面积大、纤维直径小、空隙率高等优点使其在水过滤、气过滤方面拥有巨大的发展潜力。无论是哪种形式的膜材料,研究者们都致力于对过滤膜在高效化、功能化和环境友好性方面展开深入的研究。     

高效空气过滤用PTFE膜材料的结构和性能

聚四氟乙烯(PTFE)膜高效空气过滤材料以其过滤效率高、初始阻力小和无硼释放等优点,在电子工业洁净室中得到了广泛的应用,然而目前尚缺乏PTFE膜与传统滤材结构及性能的系统对比研究。本文选取了两种商业应用的PTFE膜高效滤材,采用扫描电子显微镜、孔径分析仪、自动滤材测试仪等多种表征手段对材料的微观结构和过滤性能与超细玻璃纤维(简称玻纤)滤材进行了较为全面的对比研究,结果表明,PTFE膜本质上也是一种纤维类滤材,其纤维平均直径为60～85nm,远低于玻纤滤材的668.8nm;高效PTFE膜的过滤效率与玻纤滤材相当,且其初始阻力不及玻纤滤材的50%,但PTFE膜滤材的容尘性能不及玻纤滤材,更适合应用于有再生或预过滤装置的场所。     

Air filtration performance of nanofiber membranes with different morphologies produced by green electrospinning

To further target product development with low environmental impact, an integral green electrospinning (G-ES) approach has been adopted through the simultaneous application of various strategies, such as the use of biopolymers, reduction of energy use to avoid melting temperatures, and selection of non-toxic solvents and surfactants. Green solubility spinnability maps for cellulose acetate (CA), poly ε-caprolactone (PCL), and polyvinyl alcohol (PVA) are presented. Green electrospinning (G-ES) allows the production of new morphologies for CA and PCL nanofiber membranes. In this work, CA exhibits a ribbon-like morphology, PCL shows a honeycomb-like morphology and PVA cylindrical fibers. Membrane morphologies are compared with filtration efficiency (FE) for particle size of 1.0 μm and quality factor (Q_F) at a volumetric flux of 27.63 cm⁻¹. For CA is between 83% and 96% and high Q_F = 0.31–0.38 Pa⁻¹, PCL is 92% and 99% and high Q_F = 0.28–0.21 Pa⁻¹ and for PVA between 96% and 99% and high Q_F = 0.14–0.08 Pa⁻¹. These results suggest that the hierarchical nanofiber structure improves filtration performance because of the reduction in pressure drop and increase in PM interception. CA ribbon-like fibers favored air filtration performance, followed by PCL honeycomb-like fibers.     

Drying characteristics and modeling of yam slices under different relative humidity conditions

The drying characteristics of yam slices under different constant relative humidity (RH) and step-down RH levels were studied. A mass transfer model was developed based on Bi-Di correlations containing a drying coefficient and a lag factor to describe the drying process. It was validated using experimental data. Results showed that the drying air with constant RH levels of 20, 30, and 40%, temperature of 60°C, and air velocity of 1.5 m/s had an insignificant effect on drying time. This phenomenon was likely attributed to the fact that higher RH led to a rapid increase in sample’s temperature. The higher sample temperature could provide an additional driving force to water diffusion and thereby promote the moisture movement, which could minimize the negative effect of lower the drying rate in the initial drying stage. Applying air with 40% RH for 15 min in the initial stage achieved the desired color and reduced the drying time by 25% compared to the drying time under continuous dehumidification from an initial RH of 40%. Using the developed Bi-Di correlation, the estimated Biot number, effective moisture diffusivity, and mass transfer coefficient ranged from 0.1024 to 0.1182, 1.1133 × 10^?10 to 8.8144 × 10^?9 m²/s, and 1.8992 × 10^?9 to 1.7364 × 10^?7 m/s, respectively. A rather high correlation coefficient of determination (R² between 0.9871 and 0.9971) was determined between the experimental and predicted moisture contents. The present findings contribute to a better understanding of the effect of relative humidity on drying characteristics. The developed Bi-Di correlation provided a new method to determine the effective diffusivity of moisture in drying.     

相对湿度对质子交换膜燃料电池性能影响的模型研究

采用全电池催化层模型建立一个沿流道方向的燃料电池二维综合数值模型,研究不同供气湿度条件下膜内水迁移过程及其对输出性能的影响。计算结果显示：阴极进口相对湿度从100%变为10%,阴极侧膜失水导致电解质膜欧姆极化损失由0.15 V增大至0.36 V;随着相对湿度减小氧气浓度增大,阴极活化极化损失由0.45 V减小为0.22 V。模型预测的不同相对湿度条件下极化曲线和文献中实验数据吻合很好。     

IN SITU visualization of water adsorption in cellulose nanofiber film with micrometer spatial resolution using micro-FTIR imaging

Hygroscopic behavior is an inherent characteristic of nanocellulose film which strongly affects its applications. In order to gain a better understanding of water adsorption, micro-Fourier transform infrared (FTIR) imaging was used to investigate the water adsorption in cellulose nanofiber film with a spatial resolution of 20 um. Four spectral peaks at 2905?cm^?1, 1428?cm^?1, 1371?cm^?1, and 1317?cm^?1 attributed to CH and CH₂ groups were used to generate 2D micro-FTIR images of cellulose distribution, and the most intense peak at 3348?cm^?1 was employed to generate 2D micro-FTIR image of OH group distribution. On this basis, difference 2D micro-FTIR images of OH group distribution at different relative humidity (RH) levels demonstrated the development of adsorbed water distribution in cellulose nanofiber film during the water adsorption process. The study results confirmed that the micro-FTIR imaging was one promising tool for in situ visualization of water adsorption with micron-scale resolution.     

Impact of multilayering on the filtration performance of clean air filter media

Fibrous filter media are commonly used to remove airborne particles that are harmful to human health and the environment. Although filter media are often multilayered for various reasons, no systematic study of the impact of multilayering on filter media performance has been reported. In this paper, direct numerical simulations with the lattice Boltzmann method are used in order to shed light on the impact of multilayering on the performance of clean bimodal fibrous filter media in a Stokes flow regime. Virtual model clean filter media with up to eight layers and various fibre formulations are compared in terms of permeability or pressure drop, capture efficiency, and quality factor. A careful analysis of the results revealed that multilayering had no statistically significant impact on the performance of the clean filter media. At best, the impact of multilayering was similar to that of the inherent variability of such random structures. Fibre formulation was found to be a more efficient way of improving the performance of the filter media. Placing interlayered air gaps between fibrous layers also slightly improved the quality factor by facilitating the flow at the interfaces of the fibrous layers. These findings will guide future studies on the performance of multilayered filters with more complex flow conditions, such as those encountered with inertial or nanofibre-made filter media and with the fouling of filter media.     

温度和相对湿度对褐煤干燥动力学特性的影响

为确定褐煤干燥最佳工艺参数,在恒温恒湿热风干燥实验台上进行了温度为50～90℃,相对湿度为10％～30％条件下的褐煤颗粒热风干燥实验.将实验数据与9种经验、半经验模型进行拟合,利用相关系数、方差、均方根误差3种统计学参数对不同模型进行评价.结果表明:Page模型相比其他模型更适合用于描述干燥过程中褐煤颗粒水分随时间的变...     

Investigation on the hysteretic force of droplet on hydrophilic and hydrophobic surface

表面上液滴欲移动时所表现出的滞后现象尚未在理论上得到完全解决,其中液滴所受到的滞后阻力的分析和计算是定量描述此滞后现象的关键问题之一。本文应用高速摄像,实验研究了亲/疏水表面上液滴的滞后阻力,并依据相应的实验数据对滞后阻力进行了分析和验证。结果表明：液滴在亲水和疏水表面上运动时所受到的滞后阻力分别与铺展功和黏附功相对应。滞后阻力反映了液滴在亲/疏水表面上出现滞后现象的本质,同时对于进一步研究接触角滞后提供了理论基础。     

Effect of air blowing on the morphology and nanofiber properties of blowing‐assisted electrospun polycarbonates

Polycarbonate (PC) nanofibers are prepared using the air blowing‐assisted electrospinning process. The effects of air blowing pressure and PC solution concentration on the physical properties of fibers and the filtration performance of the nanofiber web are investigated. The air blowing‐assisted electrospinning process produces fewer beads and smaller nanofiber diameters compared with those obtained without air blowing. Uniform PC nanofibers with an average fiber diameter of about 0.170 μm are obtained using an applied voltage of 40 kV, an air blowing pressure of 0.3 MPa, a PC solution concentration of 16%, and a tip‐to‐collection‐screen distance (TCD) of 25 cm. The filtration efficiency improvement of the air blowing‐assisted electrospun web can be attributed to the narrow distribution of fiber diameter and small mean flow pore size of the electrospun web. Performance results show that the air blowing‐assisted electrospinning process can be applied to produce PC nanofiber mats with high‐quality filtration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011