纳米SiO_2驻极体/聚乳酸复合熔喷非织造材料的制备及性能

采用纳米SiO_2为驻极体,经过表面改性与聚乳酸(PLA)复合,利用双螺杆挤出机制备了纳米SiO_2/PLA复合熔喷切片,并通过工业级熔喷生产线试制了纳米SiO_2/PLA复合熔喷非织造材料。利用FTIR分析了纳米SiO_2的表面改性效果,利用DSC分析了纳米SiO_2/PLA复合熔喷切片在熔喷快速冷却条件下的结晶性能,利用滤料综合性能测试台和SEM研究了纳米SiO_2/PLA复合熔喷非织造材料的过滤性能及微观形貌,最后采用质量损失法评估了纳米SiO_2/PLA复合熔喷非织造材料的降解性能。研究结果表明:经表面改性处理,纳米SiO_2表面附上了有机活性基团;在100℃/min的冷却条件下纯PLA的结晶分数较低,纳米SiO_2驻极体的加入有助于PLA的结晶;少量纳米SiO_2驻极体的添加可显著提高PLA复合熔喷非织造材料的过滤效率,其中质量分数0.75%的纳米SiO_2添加量可使过滤效率达到99.69%,接近商用高效空气过滤器(HEPA)级聚丙烯(PP)过滤效率;在中性水解环境下,纳米SiO_2/PLA复合熔喷非织造材料具备可降解性能,经8个月质量降解至79.57%。     

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。      

驻极体-增塑剂复合改性聚乳酸熔喷非织造材料的制备及性能

分别采用无机纳米SiO₂或一种商用有机助剂（O-electret）作为驻极体改性剂,并通过引入环氧大豆油（ESO）和聚乙二醇（PEG）作为增塑剂对聚乳酸（PLA）进行了复合改性,在传统工业熔喷生产线上制备了具有可生物降解特性的驻极体-增塑剂/PLA熔喷非织造复合材料。利用转矩流变仪和熔融指数仪测试了复合改性PLA切片的流动性,发现加入ESO和PEG能使熔融指数提高到110 g/10 min。利用DMA测试了驻极体-增塑剂/PLA熔喷非织造复合材料的力学性能,发现采用增塑剂改性后能显著提高材料的拉伸强度和塑性。利用滤料综合性能测试台测试了的驻极体-增塑剂/PLA熔喷非织造复合材料的过滤性能,结果显示,驻极改性能够使其过滤PM2.5的效率提高至86%及以上。利用SEM研究了驻极体-增塑剂/PLA熔喷非织造复合材料表面的微观形貌,结果表明,采用驻极体改性后,细纤维的比例显著增加;采用增塑剂改性使纤维更细更长,纤维间交错更加复杂。      

熔喷聚丙烯驻极体空气过滤材料对不同气溶胶的过滤性能及过滤机理研究

测定了熔喷聚丙烯驻极体空气过滤材料对离子型(KCl)、极性非离子型(DEHS)两种不同实验气溶胶粒子的过滤性能,研究了粒子的粒径、荷电特性及流动速率对过滤性能的影响,分析了惯性效应、扩散效应和静电效应对粒子捕获能力的贡献。结果表明,熔喷聚丙烯驻极体空气过滤材料对不同气溶胶粒子的捕获能力差别较大,对KCl气溶胶的捕获能力要优于DEHS气溶胶,其原因与驻极体空气过滤材料所具有的特殊的静电效应有关。KCl用作实验气溶胶时,不出现MPPS(最易透过粒径)现象,过滤机理以静电效应为主;DEHS用作实验气溶胶时,MPPS值在0.08μm附近,小于经典单纤维过滤值0.3μm,过滤机理以惯性效应、扩散效应为主,以静电效应为辅。     

驻极体及其在空气净化领域中的应用

传统过滤器的滤材由细小的纤维或多孔材料构成,通过直接捕获、惯性沉积、重力沉积和扩散效应等几种机理联合作用来捕获粉尘粒子。由于空气中的大多数粉尘是亚微米级粒子,传统的过滤器要滤除这些粉尘粒子,需采用处于夯实状态的纤维,这样将极大地增加流阻。而驻极体过滤器中的滤材,采用的是被极化了的纤维材料,在与气流垂直的方向上存在着高达几百至上千伏电压的静电场,从而形成了无数个无源集尘电极。当气流中的带电微粒尤其是亚微米级粒子(往往是带电的)通过这些孔隙时,就在电场力的作用下被捕获。正是由于驻极体过滤材料所具有的低流阻、高效率、除尘灭菌多功能及对具有致癌作用的亚微米级粒子突出的捕获能力,使其在医疗设施洁净、制药工业和生物制品洁净、高新科技产业洁净及旅馆酒店、家庭和公共场所洁净等方面的应用上,显示出独特的优势。在介绍驻极体的基本概念的基础上,分析了驻极体过滤材料的主导产品聚丙烯非织造布的化学结构特点和电荷存储的基本特性,综述了聚丙烯非织造布驻极体材料电荷特性和稳定性的最新研究结果,并对在开发聚丙烯非织造布驻极体空气过滤材料工艺中常用的制备方法作了评述。     

纳米银抗菌防雾霾口罩的设计与性能测试研究

以棉布、麻布、聚丙烯(PP)熔喷非织造布、活性炭布及针刺静电棉为研究对象,通过透气性能测试和颗粒物过滤性能测试评价不同材料的空气过滤性能,并筛选出具有较好过滤性能的防雾霾口罩滤片;在此基础上,以紫外还原银离子(Ag+)的方法在活性炭布表面负载纳米银(Ag)以实现其抗菌功能。并研究了还原时间、硝酸银(AgNO3)溶液用量对载银效果的影响以及载银的牢度。研究结果表明:在AgNO3溶液用量为5%(wt,质量分数)条件下载银效果最佳,以PP熔喷非织造布、针刺静电棉和活性炭布组合制成的滤片具有较好的过滤作用,对PM2.5平均过滤效率达到93.95%。     

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浴配比共制备了15组复合膜对比样品,系统研究了各关键参数对膜的透气量、孔径、过滤效率及微观形貌结构的影响。结果表明,随着三氧化二铝(Al₂O₃)/PES质量比的增加,复合膜的透气量和平均孔径先增大后减小,过滤效率由75.1%提高至81.4%;随着凝固浴温度的上升,复合膜的透气量和平均孔径不断增大,过滤效率由80.6%降至57.7%;随着第一凝固浴中乙醇含量的增加,复合膜的透气量和平均孔径不断减小,过滤效率提高至89.5%。聚醚砜/非织造布复合膜有望在空气过滤、环保等领域得到应用。     

一种用于个体防护的高效净化材料的制备与性能

目前,经驻极生产的熔喷布对空气中病毒等微小颗粒的过滤主要依靠其静电吸附机理,但由于熔喷布表面电荷难以持久保持,不能长期保持高效过滤,因而不能保证医护人员不被新型冠状病毒(COVID-19)感染,所以需要提升熔喷布在失电荷时的机械过滤效率。文中利用静电纺丝技术在熔喷布上电纺尼龙6(PA6)纳米纤维,通过热压法制成一种以熔喷布为表层,PA6纳米纤维为中间层的夹心材料;对该夹心材料的表面形貌、热学性能、力学性能进行表征并测试其过滤性能。实验结果表明,夹心材料表面完整度高,纳米纤维直径可达67 nm左右;在没有驻极工艺处理的情况下,该夹心材料对粒径为0.2μm的颗粒过滤效率达到95%以上,而对照试验的无纺布相应的过滤效率为0;该夹心材料过滤阻力在284 Pa左右,适合作为个体防护使用。     

PP/CHA熔喷非织造布制备工艺及其性能研究

介绍了PP/CHA熔喷非织造布的加工研制过程.通过对所制PP/CHA熔喷非织造布进行纤维细度、力学性能、透气性能、过滤效率和亲水性能测试,分析热空气温度和压力、接收距离等熔喷工艺参数对产品性能的影响.结果表明:纤维直径随热空气温度增加,先减小后增大;随热空气压力增大而减小.强度随热空气压力增大而增大,随接收距离增大而减小.透气率随热空气温度升高而增大,过滤效率随热空气压力增大而增大,吸液率随接收距离增大而增大.     

口罩用熔喷法非织造布生产质量控制之探讨

熔喷法非织造布有多种工业用途,其应用于口罩生产主要是基于其较好的过滤效率。在新冠疫情的影响下,口罩的高需求带动了熔喷布的高需求。本文就新冠疫情以来熔喷法非织造布的生产现状,从标准角度对生产质量控制进行了探讨。     

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。     

COMPARISONS OF MECHANICAL MELT-BLOWN FILTERS AND ELECTROSTATICALLY ENHANCED SPLIT-FIBER FILTERS FOR CABIN AIR FILTRATION APPLICATIONS

In this paper, compared are filtration characteristics of two different filters made from uncharged melt-blown media and electrostatically charged split-fiber media. The split-fiber filters have stronger electrostatic charges in the media than the melt-blown filter, which in turn enhances the initial fractional efficiency. The compared parameters are fractional efficiencies, dust holding capacities, incremental fractional efficiencies, and pressure drop. The advantages and disadvantages of these filters for cabin air filtration applications are discussed based on the experimental results obtained using SAE-fine dust and sodium chloride test aerosol. The optimization process of the filter selection is also discussed.     

AIR FILTRATION IMPROVED BY ELECTROSTATICALLY CHARGING FIBROUS MATERIALS

Particle filtration efficiency is governed by mechanical mechanisms, i.e. interception, impaction and diffusion, as well as by electrostatic mechanisms, i.e. electrostatic attraction force. The mechanical mechanisms are determined by the surface area of fibers on the web. Therefore, reducing fiber diameter improves filtration efficiency. However, filters have a low filtration efficiency for very small particles by mechanical mechanisms. The filtration efficiency is greatly improved by electrostatic charging of fibrous materials. Charging theory and charging techniques will be described. The improvement of filtration efficiency by electrostatically charging the meltblown polypropylene (PP) webs using the techniques developed at the University of Tennessee as compared with other techniques will be discussed.     

DETERMINATION OF FIBER CHARGE DENSITY OF ELECTRET FILTERS

Particle collection in electret filters is enhanced by electrostatic forces resulting from the embedded charge on the fibers of the filters. Currently, there is no simple method available for determining the charge density on the electret fibers. Since charge on the fibers can degrade with loading or during storage, a simple evaluation technique is desirable. Aerosol consisting of organic oil mist generally used for testing HEPA filters should not be used for evaluating electret filters since organic aerosol droplets rapidly degrade the electrostatic charge effect. In this study experimental measurements of penetration were made on electret filters challenged with monodisperse, polystyrene latex spheres, PLS, of known size and charge. The experimental data on penetration were used to separate the contributions of the individual collection parameters and to determine the effective density of charge on the fibers. Collection efficiency due to mechanical filtration mechanisms was measured using filters in which the electret charge had been effectively neutralized by loading the filters with an oil aerosol. Collection due to dielectrophoretic force was obtained using aerosol with zero charge. The effective charge density on the fibers was determined by comparing measurements of penetration for particles having known size and charge with the predictions of available theoretical equations. Details of this method of determining the density of charge on the fibers are described here. Experimental determinations of charge density showed reasonable agreement with the charge densities given by the manufacturers of the tested filters.     

异丙醇处理对熔喷聚丙烯驻极体空气净化材料性能和结构的影响

本文通过测试过滤效率和阻力、热刺激放电谱、X射线衍射谱以及扫描电镜观测,研究了异丙醇浸泡和熏蒸对材料驻极体性能及微观结构的影响。结果表明,异丙醇浸泡与熏蒸都可以使材料中的电荷完全消失,但不会影响材料的晶相结构。浸泡后材料的剩余过滤效率比熏蒸后的高。浸泡与熏蒸对材料过滤阻力的影响不大。     

Design of filter bag media with high collection efficiency

The various filter bag media were prepared by a nonwoven pilot plant coupled with the needle punching and thermal bonding combination processes. The prepared filter media were evaluated by the reliability assessment standard for the filter bag media of the environmental cleaning dust collector (RS K 0001). A new filter bag medium was thermal bonded with polyester felt and polyamide nano-sized web. The air permeability of the filter bag media with nano-sized web was largely reduced as compared with the control media. In the evaluation of filtration test, the filter medium with nano-sized web showed more stable filtration behavior and more higher collection efficiency than the others.     

EFFECT OF LOADING WITH AIM OIL AEROSOL ON THE COLLECTION EFFICIENCY OF AN ELECTRET FILTER

Loading of an electret filter changes the distribution of electrical field in the filter from its preloading condition, and, therefore, affects the filtration efficiency of the filter. Liquid droplets collected on electret filters cause degradation of the electrostatic enhancement of filtration efficiency because of charge neutralization and the formation of a dielectric coating over die charged fibers. In this study, calculations were made for the penetration of aerosol particles through a spun-type electret filter as a function of the particulate loading. An assumption was made that each charge collected neutralized one charge of opposite polarity on the fibers of the filter. It was also assumed that the electrostatic charges present on the particles followed the Boltzmann equilibrium charge distribution. The decrease in fiber charge and resulting increase in penetration were calculated as a function of time and of total particulate loading on the filter. The calculated penetrations were compared with experimental measurements of loading on a spun fiber electret filter challenged with monodisperse liquid droplets of bis-Ethylhexyl Sebacate with equilibrium charge distribution and with zero charge. The rate at which the penetration increased was found to be the same for particles with zero charge as for particles with equilibrium charge distribution. For 1 um diameter droplets with equilibrium charge the theory predicted complete discharge of the filter at a loading of around 200 g/m². Experimentally, only about 0.3 g/m² was required. This difference indicates the presence of additional mechanisms for the discharge of the fibers.     

EFFECT OF LOADING WITH AIM OIL AEROSOL ON THE COLLECTION EFFICIENCY OF AN ELECTRET FILTER

ABSTRACT

Loading of an electret filter changes the distribution of electrical field in the filter from its preloading condition, and, therefore, affects the filtration efficiency of the filter. Liquid droplets collected on electret filters cause degradation of the electrostatic enhancement of filtration efficiency because of charge neutralization and the formation of a dielectric coating over die charged fibers. In this study, calculations were made for the penetration of aerosol particles through a spun-type electret filter as a function of the particulate loading. An assumption was made that each charge collected neutralized one charge of opposite polarity on the fibers of the filter. It was also assumed that the electrostatic charges present on the particles followed the Boltzmann equilibrium charge distribution. The decrease in fiber charge and resulting increase in penetration were calculated as a function of time and of total particulate loading on the filter. The calculated penetrations were compared with experimental measurements of loading on a spun fiber electret filter challenged with monodisperse liquid droplets of bis-Ethylhexyl Sebacate with equilibrium charge distribution and with zero charge. The rate at which the penetration increased was found to be the same for particles with zero charge as for particles with equilibrium charge distribution. For 1 um diameter droplets with equilibrium charge the theory predicted complete discharge of the filter at a loading of around 200 g/m². Experimentally, only about 0.3 g/m² was required. This difference indicates the presence of additional mechanisms for the discharge of the fibers.