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1.
In this work, a series of needle-punched nonwoven filter media was prepared by using polyester fibres of three different cross-sections (circular, trilobal, and deep-groove) in accordance with a three-component augmented simplex lattice design. The experimental data of filtration efficiency and pressure drop were analyzed by means of response surface methodology. Statistical model equations were developed for filtration efficiency and pressure drop by using Design-Expert® software. The filtration efficiency and pressure drop were expressed as linear functions of proportion of fibres of different shapes. Statistical checks (ANOVA, R 2 and p-value) indicated that these models were adequate for representing the experimental data. By means of contour plots, the effect of filter constituents on filtration performance was analysed. The filter media consisting of deep-grooved fibres exhibited highest filtration efficiency but at the cost of highest pressure drop. On the other hand, the filter media consisting of circular fibres displayed lowest pressure drop but at the cost of lowest filtration efficiency. As a compromise for simultaneously achieving maximum filtration efficiency of 61.52 % and minimum pressure drop of 13.6 Pa, the optimum mixture was predicted to consist of 53.7 % deep grooved fibres and 46.3 % circular fibres. The predicted response was found in close agreement with the experimental data. This demonstrates the effectiveness of the approach reported here for achieving good predictions, while minimizing number of experiments.  相似文献   

2.
Two kinds of composite filter materials were prepared by regulating the structure of melt-electrospinning polypropylene (PP) webs. The self-designed multi-nozzle melt-electrospinning device was used to produce PP webs which deposited on PP spunbonded nonwoven. Firstly, the composite filter materials with different thickness and ratios of coarse/fine fibers were prepared, and the effect of the thickness and the ratio of coarse/fine fibers on filtration properties were studied. The results showed that the filtration efficiency and pressure drop increased as thickness increased. In addition, compared with the general filters which were composed of coarse or fine fibers, the filters with coarse/fine fibers had “low pressure drop” under the similar filtration efficiency. In the case of the ratio of coarse/fine fiber about 2:2, this filter achieved optimal performance. When the thickness was 0.42 mm, its filtration efficiency for particles more than or equal to 2.0 μm could reach more than 95 %. Its pressure drop and air permeability were 18.13 Pa and 54.69 mm/s, respectively, while those of general filter were 38.67 Pa and 10.02 mm/s, respectively. After that, the composite filter materials composed of various angles of oriented webs were produced. The results showed that the filtration efficiency for particles with the size of more than or equal to 2.0 μm was higher than that of filters composed of one angle of oriented webs. In addition, the lower the orientation was, the lower the pressure drop was.  相似文献   

3.
Nanofibers definitely hold great advantage and promise in filtration as they have very high specific surface area, which ensures greater probability of capturing the particles and hence, the filtration efficiency of the nanofiber filter media is high. Electrospun nanofibers are prohibitively expensive due to extremely low production rate. With recent advances in melt blowing technology, nanofibers could be produced at production rate few orders of magnitude higher than that of conventional single syringe electrospinning and hence, quite cost effective. Influence of air pressure and die to collector distance (DCD) were studied on the number average fiber diameter for the nanofibers as well as the performance properties of the nonwoven webs, each factor at three discrete levels. The nanofibers were as fine as 260 nm. A very encouraging observation of the study is very high values of quality factor observed for nanofiber nonwoven filter media. In order to compare the filtration efficiency of different nanofiber nonwoven media samples with different basis weight, a novel term of specific filtration efficiency is proposed and was found that the specific filtration efficiency with the increase in DCD or air pressure.  相似文献   

4.
Solution blowing process is a new nanofiber fabricating method with high productivity. In the present study, nylon 6 nanofiber mats were solution blown and the effects of spinning conditions on nanofibers morphology were investigated. The fiber diameter ranged from 150 to 750 nm which was affected by solution concentration, gas pressure and solution feeding rate. The solution blown fibers were three-dimensional curly which made loose construction in bulk. The filtration performance of solution blown mats was evaluated. The tested solution blown nanofiber mats showed high filtration efficiency of 83.10 % to 93.45 % for 0.3 µm particles filtration and extremely low pressure drop of 15.37 to 30.35 Pa. The results indicate the solution blown nanofiber mats will find potential application of high efficiency and low resistance filter.  相似文献   

5.
Polyimide (P84) nanofibers of 200-500 nm were deposited uniformly on needle punched aramid felt with basis weight of 260-350 g/m2 by optimized electrospinning. High temperature adhesive was then electro-sprayed on the nanofiber side deliberately to bind a thin protective layer made of temperature-resistant non-wovens. The three layer structure was afterwards enforced by hot pressing to form composite filter media. The application of the adhesive was tailored not to affect the permeability of the substrate felt while exerting adhesion strength of over 1000 kPa for the media to be suitable for flue gas dust treatment under 240 ºC. When 0.3-10 μm NaCl aerosols were used as the simulated dusts, it was found that even a small amount of P84 nanofibers could obviously elevate the filtration efficiency. The composite showed 100 % removal efficiency of particles equal and greater than 2.0 μm, and 99.5 % for particles 1.0-2.0 μm in diameter.  相似文献   

6.
In this paper, we discussed the relationship of filter efficiency and pressure drop with the porosity, fiber diameter and filter thickness by Geodict®. We found that filter efficiency has exponential relationship with filter porosity, fiber diameter and thickness. Furthermorethe pressure drop has a linear relationship with filter thickness and exponential relationship with filter porosity and fiber diameter, respectively. The influence of electrostatic charge on the particle deposition has been investigated. Simulation results were compared with the actual test results by TSI 3160.  相似文献   

7.
In order to obtain paper respirator with dust resistance performance and antibacterial property, silk photo-catalytic respirator paper was made by loading nano-TiO2 photo-catalyst on silk based respirator paper. The pore structure, surface topography and TiO2 distribution, and the filtration performance of silk respirator paper were studied by using a pore size meter (PSM), a field emission scanning electron microscope (FESEM), and a filter tester, respectively. In addition, the antibacterial property of silk respirator paper was also investigated. The results showed that the pore structure and filtration performance of silk respirator paper could be controlled by changing the degree of beating of silk pulp and the basis weight of silk paper. Silk respirator paper of 45 g/m2 made from silk pulp having beating degree of 85 oSR had high filtration efficiency and appropriate filtration resistance. Nano-TiO2 particles were mainly attached to the surface of silk paper, and the loading of nano-TiO2 photo-catalyst resulted in a slight decrease in filtration resistance and filtration efficiency of silk respirator paper. It, however, improved the antibacterial property of silk respirator paper effectively.  相似文献   

8.
Accurate modeling of fibrous filter pressure drop and particle capture/loading behavior includes many phenomena, including partial-to-full slip flow at fiber boundaries, random fiber location and orientation, particle/fiber and particle/particle adhesion and bouncing. Filter media fibers are usually joined together by binders which form significant percentages of the solid material in the media. Complete simulation of media geometry would be three-dimensional (3-D). However, complex 3-D geometries in computational fluid dynamics (CFD) demand powerful computing resources, and hence have been limited to a few fibers. Studies using 2-Dimensional (2D) models were effective in predicting media airflow resistance and particle capture for simple geometries. More realistic 2-D simulations reflecting the random diameter distribution and positioning of fibers with appropriate local boundary conditions should allow still better predictions. To this end we measured the geometric properties of three glass fiber media. 2-D models of fibers with binder links were developed. Statistical fiber diameter distributions were evaluated to determine which provided closer agreement with the measured fiber diameter distributions under the geometric constraints present. For the high standard deviations of fiber diameters present in these media, the number of fibers needed for valid statistics is rather large, which means that complete 3-D simulations are probably not practical.  相似文献   

9.
In this study, two composite nanofibrous membranes of Polyvinylidenefluoride (PVDF) and [poly(vinylidenefluorideco-hexafluoropropylene)] (PVDF-co-HFP) prepared by the electrospinning process were employed in a direct contact membrane distillation (DCMD) system. We changed the pump flow rate and temperature difference to examine their effects on permeate flux and salt rejection. The SEM observations, porosity analyzer technique, and contact angle measurement indicated the nanobrous membrane with an average fiber diameter of 170 nm and maximum pore diameter distribution of 0.3 ??m is the best membrane for the DCMD system. However, the ability of the hydrophobic membrane affects the filtration efficiency of the DCMD system. The contact angle of the PVDF-HFP electrospun membrane (128°) shows better hydrophobic than the PVDF electrospun membrane (125 °). From the experiment of 12 hours, the salt rejection of PVDFHFP (99.9901 %) was better than that of PVDF composite membrane (99.9888 %) and was almost the same as that of the PTFE commercial membrane (99.9951 %). In addition, the permeate flux of the PVDF-HFP composite membrane is 4.28 kg/ m2hr higher than the PTFE commercial membrane.  相似文献   

10.
Compression athletic wear (CAW) is used in number of active sports like jumping, running and power lifting etc. to enhance the performance of an athlete. Compression efficiency is mainly determined by interface pressure exerted by it but pressure reduces with time due to prolonged stretching and deformation of fabric. In this study, compression behaviour was evaluated by measuring the interface pressure drop and recovery characteristics of CAW. Interface pressure over a long duration of time was measured using a dynamic leg segment prototype. Recovery characteristic was evaluated by measuring the residual shrinkage at different time interval using cyclic fatigue test. The effect of filament cross sectional shape, Lycra® linear density and fabric tightness on compression properties was found to be statistically significant by ANOVA. Fabric with high tightness factor, coarse Lycra® and profiled polyester was observed to have better recovery and compression efficiency as compared to other fabrics under study.  相似文献   

11.
We report the microstructures and electrical properties of poly(2-cyano-1,4-phenylene terephthalamide) (cyPPTA)-based composite films including pristine multi-walled carbon nanotube (MWCNT) of 0.3-10.0 wt%, which were manufactured by ultrasonication-based solution mixing and casting techniques. FT-IR spectra of the composite films revealed the existence of specific interaction between cyPPTA and MWCNT. Accordingly, the pristine MWCNTs were found to be dispersed uniformly in the cyPPTA matrix, as confirmed by TEM images. The electrical resistivity of the composite films decreased considerably from ~1010 Ω cm to ~100 Ω cm with the increase of the MWCNT content by forming a conductive percolation threshold at ~0.525 wt%. The composite films with 3.0-10.0 wt% MWCNT contents, which have sufficiently low electrical resistivity of ~102-100 Ω cm, exhibited excellent electric heating performance by attaining high maximum temperatures and electric power efficiency under given applied voltages of 10-100 V. Since the thermal decomposition of the composite films took place at 520-600 °C under air atmosphere, cyPPTA/MWCNT composite films could be used for high performance electric heating, antistatic, and EMI shielding materials.  相似文献   

12.
As a kind of high-performance fibers, PTFE fiber has been widely used in many fields because of its unique characteristics. In this study, the poly(tetrafloroethylene) (PTFE) nanofibers manufactured by electrospinning method was reported. The gel-spinning solution of poly(tetrafluoroethylene)/poly(vinyl alcohol)/boric acid (PTFE/PVA/BA), which was prepared by the gel process of the mixture of PTFE, PVA, BA and redistilled water, was electrospun to form PTFE/PVA/BA composite nanofibers. After calcinating, the PTFE nanofibers with diameters of 200 nm to 1000 nm were obtained. The fibers before and after calcinating were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), FT-IR spectrum analysis and X-ray photoelectron spectroscopy (XPS), respectively, and the mechanical and hydrophobic properties of the fibers were also investigated. The results showed that the PTFE nanofiber membranes could be electrospun effectively used the gel-spinning solution of PTFE/PVA/BA, and may realize the applications in the fields of high-temperature filtration, catalyst supports, battery separator and so on.  相似文献   

13.
The objective of this study was to examine the filtration characteristics of ground kenaf core, a waste material generated during the production of kenaf bast fibers for paper. The constant-pressure precoat filtration characteristics of ground kenaf core were compared to commercial diatomaceous earth (DE). Three challenge solutions were studied: a yeast solution, a bacterial solution, and a standard silica-particle solution. The kenaf and DE both satisfactorily permitted removal of all silica particles from solution without noticable flux degradation over the course of the filtration. The kenaf and DE also removed yeast particles. In this case, the flux loss with time was lower with the DE precoated filter than in the kenaf precoated filter. The DE precoat excluded less than 10% of the bacterial particles from solution, whereas the kenaf removed about 40% of these small particles.  相似文献   

14.
A novel thin film nanofibrous composite (TFNC) polyphenylsulfone (PPSU) membrane was fabricated by casting a thin PPSU barrier layer on the surface of the electrospun nanofibrous PPSU support. Polyethylene glycol (PEG) 400 was applied in the electrospinning solution to prevent the penetration of coating solution into the support. The membrane morphology and filtration performance were investigated via scanning electron microscopy (SEM), and filtration of canned beans production wastewater, respectively. Atomic force microscopy (AFM) was utilized to evaluate the surface roughness of the membranes. Furthermore, the mechanical strength and thermal stability of the membranes were determined via tensile test and thermogravimetric analysis (TGA). Comparison of the TFNC membrane and the unsupported membrane prepared through the wet phase inversion method with almost equal rejection values indicated a 2.3 fold higher PWF using the former.  相似文献   

15.
A fibrous composite membrane consisting of a chitosan (CS) barrier layer and a poly(hydroxybutyrate-cohydroxyvalerate) (PHBV) fibrous substrate was manufactured as a filter for water purification. The PHBV fibrous supporting layer was fabricated via electrospinning technique, and then the CS solution cast on the PHBV fibers to form the top barrier layer. The structural morphology, mechanical property and adsorption capability of the PHBV/CS membranes were thoroughly investigated. Three heavy metal ions were used to evaluate the equilibrium absorption capacities of the chosen membranes. The equilibrium absorption capacities for Cu(II), Pb(II) and Cd(II) were 64.08 mg/g, 90.32 mg/g and 148.96 mg/ g, respectively. Meanwhile, the rejection ratio of PHBV/CS composite membrane for two disperse dyes could reach to 99 %. The results indicated that PHBV fibrous substrate could not only enhance the mechanical strength of the top barrier layer, but also improve the water permeation of the membrane. This study extended the application of an environmentally friendly material in the water purification without causing much trouble about scrap film.  相似文献   

16.
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17.
The use of nonwoven textile substrates for filtration and absorption purposes is generalized due to the high surface area they can provide. Many of these applications require good wetting properties to increase efficiency. In this work, low pressure plasma treatment with a CH4-O2 mixture gas has been used to increase surface wettability and subsequent absorption properties on nonwoven polypropylene substrates. CH4 plasma treatment leads to a plasma polymerization process which results in hydrophobic surface finishing, but in combination with O2, it is possible to form a functionalized plasmapolymerized layer thus improving wetting properties. Changes in wetting properties have been studied by contact angle measurements showing that optimum wetting properties are obtained with exposure times to plasma treatment of about 10 min, and no significant changes are obtained for longer exposure times. Absorption efficiency has been followed by determining three different parameters by the guidelines of the UNE-EN-ISO 9073-6 standard: wetting time, liquid absorption capacity (LAC) and liquid propagation rate or absorption speed. All these properties are remarkably improved as the exposure time to CH4-O2 plasma increases; this improvement is remarkably high for relatively short exposure times (5?C10 min) and no significant changes are obtained for long exposure times so that, it is possible to conclude that previous plasma treatment with exposure times in the 5?C10 min range is an efficient method to improve overall absorption properties of nonwoven polypropylene substrates.  相似文献   

18.
The inner-skinned hollow fiber composite (HFC) nanofiltration (NF) membranes were modified through the incorporation of zinc oxide nanospheres in the poly(piperazine amide) layer during the interfacial polymerization (IP) process. The active layer was coated on the inner surface of polysulfone (PSF) support membrane via Two-way coating technique. The chemical composition and morphology of HFC membrane surface were evaluated through the Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) and Scanning Electronic Microscopy (SEM). The effects of zinc oxide (ZnO) nanospheres on membrane performance including the hydrophilicity, separation performance and chlorine resistance were investigated. The results showed that the modified HFC membranes with low concentration ZnO nanospheres (1.5 wt%) had an improved flux (33.8 L·m-2·h-1) meanwhile the salt rejection of MgSO4 was well maintained (92.2 %) at 0.7 MPa. The introduction of ZnO also dramatically enhanced the chloride resistance of composite NF membranes in comparison with the control membranes prepared without ZnO. Therefore, nano metallic oxide like ZnO could be considered as a potential modifier to improve the performance of HFC nanofiltration membranes.  相似文献   

19.
大豆适应低磷胁迫的机理初探   总被引：20，自引：8，他引：20  
王应祥  廖红  严小龙 《大豆科学》2003,22(3):208-212
通过营养液栽培试验研究大豆适应低磷胁迫的机理，试图找出供试大豆在水培条件下对低磷胁迫下的适应性与田间表现的关系，为快速选育磷高效品种提供具有参考价值的实验数据。结果表明：在水培条件下，大豆在磷效率方面存在着显著的基因型差异。在总体磷效率(以生物量为标准)方面和磷吸收效率(整株含磷量)方面，结果与田间试验表现基本一致。BX10和GD1属于磷高效对磷不敏感基因型，BD2属于磷低效对磷不敏感基因型，BX11和GD2属于磷低效对磷敏感基因型，BD1属于磷高效对磷敏感基因型，GD3和GD4表现不稳定。从磷的利用效率(单位磷所产生的生物量)来看，基因型间没有显著差异。说明即使在水培条件下，磷利用效率对大豆总体磷效率贡献也不大，大豆总体磷效率主要是由吸收效率决定的。与田间反应不同的是，水培条件下磷吸收效率高的基因型，具有较长的根长与较大的根表面积。说明在介质有效磷分布均匀的条件下，根形态性状对磷吸收效率起一定的作用。  相似文献   

20.
The synthesis of titanium dioxide nanofibers with 200–300 nm diameter was presented. The new inorganic-organic hybrid nanofibers were prepared by sol-gel processing and electrospinning technique using a viscous solution of titanium isopropoxide (TiP)/poly(vinyl acetate) (PVAc). Pure titanium dioxide nanofibers were obtained by high temperature calcination of the inorganic-organic composite fibers. SEM, FT-IR, and WAXD techniques were employed to characterize these nanofibers. The titanium dioxide nanostructured fibers have rougher surface and smaller diameter compare with PVAc/TiP composite nanofibers. The anatase to rutile phase transformation occurred when the calcination temperature was increased from 600 °C to 1000 °C.  相似文献   

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