首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 468 毫秒
1.
As nonwoven mats are randomly oriented fiber assemblies, the tensile strength of nonwoven mats is determined by their microstructural factors, such as fiber orientation, fiber volume fraction, and fiber-fiber contact level. The complex microstructure of nonwoven mats must be reasonably simplified to properly predict their mechanical properties within affordable efforts. In this study, a new parameter, so called contact efficiency, is defined to describe the fiber-fiber contact level of nonwoven mats. Micro X-ray computer tomography (CT) is employed to characterize the microstructure of needlepunched nonwoven mats made of polypropylene short fibers. The fiber orientation and volume fraction are obtained by analyzing 2D sectional CT image of the nonwoven mat, while the contact efficiency is determined from 3D CT image. A statistical model, developed originally for staple yarns, is modified to predict the tensile strength of the nonwoven mat using the microstructural factors obtained from CT analysis. The prediction is then compared with experiments to validate that the current model incorporating the contact efficiency is highly suitable for predicting the tensile strength of nonwoven mats.  相似文献   

2.
In this study, electrospun wool keratose (WK)/silk fibroin (SF) blend nanofiber was prepared and evaluated as a heavy metal ion adsorbent which can be used in water purification field. The WK, which was a soluble fraction of oxidized wool keratin fiber, was blended with SF in formic acid. The electrospinnability was greatly improved with an increase of SF content. The structure and properties of WK/SF blend nanofibers were investigated by SEM, FTIR, DMTA and tensile test. Among various WK/SF blend ratios, 50/50 blend nanofiber showed an excellent mechanical property. It might be due to some physical interaction between SF and WK molecules although FTIR result did not show any evidence of molecular miscibility. As a result of metal ion adsorption test, WK/SF blend nanofiber mats exhibited high Cu2+ adsorption capacity compared with ordinary wool sliver at pH 8.5. It might be due to large specific surface area of nanofiber mat as well as numerous functional groups of WK. Consequently, the WK/SF blend nanofiber mats can be a promising candidate as metal ion adsorption filter.  相似文献   

3.
Electrically conductive nanofibers were fabricated from elastic polyurethane (PU) and PU/multiwalled carbon nanotubes (MWCNTs) nanocomposite by electrospinning method. The nanocomposites were electrospun at various MWCNTs loading. Electron microscopy was used to investigate nanofibers morphology and dispersion of MWCNTs in the electrospun nanofibers. The results showed that the presence of the MWCNTs promoted the creation of fibrous structures in comparison with the PU without MWCNTs. On the other hand, increasing the MWCNTs content resulted in a slight increase in the average fiber diameter. TEM micrographs and mechanical properties of the electrospun mats indicated that the homogeneous dispersion of MWCNTs throughout PU matrix is responsible for the considerable enhancement of mechanical properties of the nanofiber mats. Electrical behavior of the conductive mats was also studied, in view of possible sensor applications. Cyclic experiments were conducted to establish whether the electrical properties were reversible, which is an important requirement for sensor materials.  相似文献   

4.
In order to realize flexible organic light emitting diode (OLED), it is critically important to protect moisture and oxygen penetration into the flexible device through the polymer substrates because of intrinsically poor stability of organic materials of OLED to moisture. Since complete protection of the moisture penetration is almost impossible, moisture absorbents are used inside OLED. In this study, metal oxide/polymer hybrid nanofiber with mechanical flexibility and efficient moisture absorption capability was fabricated by electrospinning. Hydrophilic poly(vinyl pyrrolidone) (PVP) or hydrophobic poly(vinylidenefluoride) (PVDF) and calcium oxide (CaO) were used as the fiber forming polymers and as the moisture absorbing particle, respectively. Polymers were first dissolved in appropriate solvents and CaO was then dispersed in the prepared polymer solutions. The hybrid solution was then electrospun, producing the hybrid nanofiber web looking like paper with thickness of about 100 µm. It was observed that all CaO particles were uniformly held by the nanofiber. It was also observed that only a small portion of the surface of CaO particles was covered by fiber since the fiber diameter was much smaller than the CaO particle size. This implied effective moisture absorption through the free surface of CaO. The hybrid nanofiber absorbed moisture very efficiently upto about 70 % of the nanofiber mass. Once moisture was absorbed by the nanofiber, it was never released even at 150 °C in vacuum for 2 hours. It is, therefore, expected that the nanofiber may be applied as the flexible thin moisture absorbent to improve stability of the flexible OLED.  相似文献   

5.
This paper reports on the preparation and characterization of nanofibers and nanofiber/film composites fabricated by electrospinning and dip-coating. The polymers in this study consist of polyurethane, nylon-6, and silicone. Scanning electron microscopy (SEM), fiber distribution, X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and tensile tests were conducted. The electrospun nylon-6 nanofiber/dip-coated silicone film (dried for 5 min) showed the optimum tensile strength and strain results, showing an increase in tensile strength of 63 % compared to pure nylon-6 nanofiber alone. XRD and FTIR verified the presence of individual polymers in the composite matrix. The electrospun PU nanofiber produced the biggest fiber diameter, while electrospun nylon-6, and PU/nylon-6 produced uniform fiber diameters, with PU/nylon-6 obtaining very random and curved fiber morphology.  相似文献   

6.
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   

7.
Silk fibroin (SF) nanofibers were prepared by electrospinning and their application as an enzyme immobilization support was attempted. By varying the concentration of SF dope solution the diameter of SF nanofiber was controlled. The SF nanofiber web had high capacity of enzyme loading, which reached to 5.6 wt%. The activity of immobilizedα-chymotrypsin (CT) on SF nanofiber was 8 times higher than that on silk fiber and it increased as the fiber diameter decreased. Sample SF8 (ca. 205 nm fiber diameter) has excellent stability at 25°C by retaining more than 90 % of initial activity after 24 hours, while sample SF11 (ca. 320 nm fiber diameter) shows higher stability in ethanol, retaining more than 45% of initial activity. The formation of multipoint attachment between enzyme and support might increase the stability of enzyme. From these results, it is expected that the electrospun SF nanofibers can be used as an excellent support for enzyme immobilization.  相似文献   

8.
Functionalization of cellulosic nanofibers was established to develop antibacterial bandages. The functionalization was conducted through preparation of carboxymethyl cellulose (CMC) containing different metal nanoparticles (MNPs) such as copper nanoparticles (CuNPs), iron nanoparticles (FeNPs) and zinc nanoparticles (ZnNPs). Fourier Transform Infrared spectroscopy was used to characterize CMC containing MNPs and scanning electron microscopy coupled with high energy dispersive X-ray (SEM-EDX) to study the surface morphology of CMC with and without MNPs. Furthermore, back scattering electron detector was used to show the position of metal nanoparticles on the microcrystalline CMC. In addition, UV-visible spectroscopy was used to confirm MNPs formation. Nanofiber mats of CMC containing MNPs were synthesized using electrospinning technique. Surface morphology of electrospun CMC containing MNPs was characterized using SEM. The obtained data revealed that elctrospun CMC nanofibers containing MNPs were smooth and uniformly distributed without bead formation. The average fiber diameters were in the range of 150 to 200 nm and the presence of MNPs in the nanofiber did not affect the size of the electrospun nanofiber diameter. Transmission electron microscopy (TEM) images displayed that MNPs were existed inside and over the surface of the electrospun nanofibers without any agglomeration. The average particle diameters of MNPs were 29-39 nm for ZnNPs, 23-27 nm for CuNPs and 22-26 nm for FeNPs. Moreover, Water uptake of electrospun nanofiber mats and the release of MNPs from nanofibers were evaluated. Nevertheless, electrospun CMC nanofibers containing MNPs had an excellent antibacterial activity against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus.  相似文献   

9.
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   

10.
In this study, two kinds of polyacrylonitrile (PAN) (carbon fiber grade PAN and oxidized fiber grade PAN) are used as the raw materials for a PAN-based nanofiber nonwoven that is prepared using electrospinning. A high-temperature erect furnace is then used, which uses oxidization processes to prepare oxidized nanofiber nonwovens in a continuous manufacturing process. The parameters used for the oxidation process are oxidation temperatures of 150, 200, 250, 275, 300 and 300 °C, which correspond to a production rate of 3, 5 and 10 cm/min at 5-cN tension. The variation in the yield rate, the breaking strength and the shrinkage of the oxidized PAN based electrospun nonwovens are examined in this study. The results demonstrate that the limit oxygen index (LOI) and aromatization index (AI) increase as the production rate decreases. Under the optimum oxidation conditions, higher quality oxidized electrospun nonwovens are produced using carbon fiber grade PAN with AI of 61 % and LOI of 42 %.  相似文献   

11.
A series of blend nanofiber mats comprising poly(vinyl alcohol) (PVA) and polyurethane (PU) were prepared by dual-jet electrospinning in various parameters. Orthogonal experimental design was used to investigate how those parameters affected on fiber diameters and fiber diameter distribution. Altogether three parameters having three levels each were chosen for this study. The chosen parameters were tip-to-collector distance (TCD), voltage and tip-to-tip distance (TTD). Fiber diameters, thermal properties, mechanical properties and hydrophilicity of the blend nanofiber mats were examined by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), tensile test, contact angle and water absorption test, respectively. The results showed that the optimum conditions for PVA/PU blend nanofiber mats fabricated by dual-jet electrospinning were TCD of 20 cm, voltage of 18 kV and TTD of 4 cm. Besides, the thermal stability of PVA/PU blend nanofiber mats had been improved compared with pure nanofibers. Furthermore, the elongation and tensile strength of the blend nanofiber mats were significantly increased compared with pure PVA and pure PU, respectively. And the blend nanofiber mats exhibited well hydrophilicity.  相似文献   

12.
Fiber mats were obtained by using a modified rotary-jet spinning system, which allows a forced air flow produced by an air compressor to interfere with the polymer jets. The main focus of current studies rely on the range of morphological and dimensional characteristics of fibers that may be expected when using this new technical setup of a rotary-jet based spinning system. In fact, this work represents a proof of concept study regarding the potential of an air flow modified rotary-jet spinning for obtaining continuous fibers and nonwoven mats. The morphological examinations by scanning electron microscopy were proved the efficiency of this technique on obtaining relative homogeneous fiber mats from different raw compositions of pure and admixed, natural and synthetic polymers with different molecular masses and polydispersity degrees, like gelatin, polyurethane, and poly (vinyl chloride). The feasibility of air flow rotary-jet spinning was also tested for simultaneous independent deposition of mixed fiber mats from solutions of two polymers made in different solvents, and it was found that by carefully selecting the ratio of polymers through spinnerets number, this technique could be successfully used even in difficult solvent conditions otherwise incompatible with traditional spinning techniques. The distribution of fiber diameters was varying between nanometer scales (100–700 nm) in the case of pure polyurethane and micrometer ranges (2–12 µm) for gelatin-polyurethane mixed mats, which are convenient for various applications, from dressings and scaffolding to different filter systems. Besides the already known advantages of rotary-jet versus electrospinning, the air flow allows the control of solvent evaporation, extending the applicative range of this technique.  相似文献   

13.
Layered fabric systems with electrospun polyurethane fiber web layered on spunbonded nonwoven were developed to examine the feasibility of developing protective textile materials as barriers to liquid penetration using electrospinning. Barrier performance was evaluated for layered fabric systems, using pesticide mixtures that represent a range of surface tension and viscosity. Air permeability and water vapor transmission were assessed as indications of thermal comfort performance. Protection performance and air/moisture vapor transport properties were compared for layered fabric systems and existing materials for personal protective equipment (PPE). Layered fabric systems with electrospun nanofiber web showed barrier performance in the range between microporous materials and nonwovens used for protective clothing. Layered fabric structures with the web area density of 1.0 and 2.0 g/m2 exhibited air permeability higher than most PPE materials currently in use; moisture vapor transport was in a range comparable to nonwovens and typical woven work clothing fabrics. Comparisons of layered fabric systems and currently available PPE materials indicate that barrier/transport properties that may not be attainable with existing PPE materials could be achieved from layered fabric systems with electrospun nanofibrous web.  相似文献   

14.
Easy fabrication, porosity, good mechanical properties, and composition controllable of the electrospun nanofiber mat make this material a promising candidate for wound dressing applications. In the present study, nylon6/gelatin electrospun nanofiber mats are introduced as novel wound dressing materials. The introduced mats were synthesized by electrospinning of nylon6 and gelatin mixtures, three mats containing different gelatin content were prepared; 10, 20 and 30 wt%. Interestingly, addition of the gelatin did not affect the mechanical properties of the nylon 6, moreover the mat containing 10 wt% gelatin revealed higher mechanical properties due to formation of spider-net like structure from very thin nanofibers (～10 nm diameter) bonding the main nanofibers. Biologically study indicates that gelatin incorporation strongly enhances the bioactivity performance as increasing the gelatin content linearly increases the MC3T3-E1 cell attachment. Overall, the obtained results recommend exploiting the introduced mats as wound dressing material.  相似文献   

15.
Natural fiber reinforced polypropylene (PP) biocomposites were fabricated by blending long-and-discontinuous (LD) natural fibers (NF) with LD PP fibers. Firstly, random fiber mats were prepared by mixing NFs and PP fibers using a carding process. Then, heat and pressure were applied to the mats, such that the PP fibers dispersed in the mats melted and flowed out, resulting in the formation of consolidated sheets upon subsequent cooling. The effect of the fiber volume fraction on the mechanical properties of the bio-composites was scrutinized by carrying out tensile and flexural tests and observing the interface between the fiber and matrix. It was observed that the natural LD fiber content needs to be maintained at less than the nominal fiber fraction of 40 % by weight for the composites fabricated using the current method, which is quite low compared to that of continuous or short fiber reinforced composites. The limited fiber fraction can be explained by the void content in the biocomposites, which may be caused by the non-uniform packing or the deficiency of the matrix PP fibers.  相似文献   

16.
Cellulose nanowhisker (CNW) reinforced electrospun Bombyx mori silk fibroin (SF) nanofibers were fabricated. The morphology, structure, and mechanical properties of nanofibers were investigated by FE-SEM, TEM, FTIR, and tensile testing. It was found that the nanofiber size decreased obviously from 250 nm in the unreinforced mat to 77–160 nm in the CNW reinforced mats depending on the CNW content due to the increased conductivity of spinning dope. In the reinforced mats, the CNWs were embedded in the SF matrix separated from each other, and aligned along the fiber axis. There was a positive correlation between the CNW content and the tensile strength and Young’s modulus of reinforced mats. However the strain at break dropped gradually with the increase of CNW. When the CNW content was 2 w/w%, the tensile strength and Young’s modulus of reinforced SF nanofiber mats were about 2 times higher than those of unreinforced mat.  相似文献   

17.
Well-aligned PMIA nanofiber mats were fabricated by electrospinning and then hot-stretching along the fiber axis was used to improve the mechanical properties of nanofibers in this paper. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Differential scanning calorimetry (DSC) were used to characterize the morphology and properties of nanofibers. The results showed that the nanofibers became thinner and better alignment than the as-spun nanofibers after hotstretching, and the average diameter of the nanofibers decreased with the increasing of the tensile force. In the same time, hotstretching improved the crystallinity and T g of the as-spun PMIA nanofibers. The tensile strength and modulus of the hotstretched nanofiber mats peaked at ca.50 % and ca.196 % respectively at the tensile force of 12 N compared with the as-spun nanofiber mats.  相似文献   

18.
In this study, electrospinning of poly(ε-caprolactone) (PCL) and its optimum preparation conditions were examined in detail using various solvent systems, such as formic acid, dichloromethane/dimethyl formamide (DMF), chloroform/DMF, and dichloroethane. The average fiber diameter of the electrospun PCL mat was controlled by the solvent used with a proper concentration of PCL dope solution. Different fiber sizes (0.1, 0.8, 1.9, and 3.4 μm) of uniform PCL mats were fabricated and the effects of fiber size on surface morphology, tensile properties and cell behavior were investigated. Here, we manipulated much broader range of average fiber diameter of the mats, from nano to several micron size of fiber. It was found that the fiber diameter greatly affected topology (surface roughness) and mechanical properties of the electrospun PCL mat and consequently, they influenced the cell behavior (adhesion and proliferation) significantly. We expect that these results will provide more feasible application of electrospun PCL scaffold in tissue engineering through the co-relations in structure and property of PCL fiber mat on cell behavior.  相似文献   

19.
Electrospinning is a simple and cost-effective method to prepare fiber with nanometer scale. More importantly, 3D flexible nanofiber yarns that fabricated by electrospinning have shown excellent application prospects in smart textiles, wearable sensors, energy storage devices, tissue engineering, and so on. However, current methods for preparing electrospinning nanofiber yarns had some limitations, including low yarn yield and poor yarn structure. In this paper, a stepped airflow-assisted electrospinning method was designed to prepare continuously twisted nanofiber yarn through introducing stepped airflow into traditional electrospinning system. The stepped airflow could not only help to improve nanofiber yield, but also good for controlling the formed nanofibers to be deposited in a small area. In addition, the experimental methods of single factor variables were used to study the effects of stepped airflow pressure, applied voltage, spinning distance, solution flow rate, air pumping volume and friction roller speed on nanofiber yarn yield, nanofiber diameter, yarn twist and mechanical property. The results showed that prepared nanofiber yarns exhibited perfect morphologies and the yield of nanofiber yarn could reach to a maximum of 4.207 g/h. The breaking strength and elongation at break of the prepared yarn could reach to 23.52 MPa and 30.61 %, respectively.  相似文献   

20.
An allometrical scaling relationship between the diameter of electrospun nanofiber and solution concentration is established, the scaling exponent differs greatly between different polymers and the same polymer with different molecules or the same molecules with different properties. The diameter of electrospun polyacrylonitrile (PAN) nanofibers increases approximately linearly with solution concentration.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号