动态线性电极静电纺PVA纳米纤维的可纺性

为了解决传统针式静电纺针头易堵塞不易产业化的问题,采用铜丝动态线性电极静电纺丝技术对PVA纳米纤维的可纺性进行研究。利用扫描电子显微镜研究了PVA溶液浓度、电压和纺丝距离对PVA纤维形貌及直径分布的影响。结果表明:随PVA溶液浓度降低,溶液粘度和电导率减小,纤维直径及其分布变小。且随纺丝距离增大,纤维直径变细,纤维形貌变好。当PVA浓度为10%(质量分数),电压80 kV,距离30 cm时,可制备出形貌良好的纳米纤维,其直径为433 nm,产量高达 6.8 g/h ;当PVA浓度为5%(质量分数),电压80 kV,距离30 cm, 可纺最细纤维直径为96 nm。本研究可为未来PVA静电纺纳米纤维膜的规模化制备提供参考。     

工艺参数对喷气式静电纺的产量和纳米纤维形貌的影响

以提高PAN纳米纤维的产量为目的,根据喷气静电纺丝的原理,设计了一种新型静电纺丝装置。研究了不同通气速度、溶液输入速度、电压等工艺参数对纳米纤维毡的产量和面积的影响。研究发现,该静电纺丝装置极大地提高了纳米纤维的产量,使产量达到普通针头产量的二十倍以上。通过研究电压对纳米纤维毡的产量和面积以及纳米纤维的微观形貌的影响,发现纳米纤维的产量随电压的增加而增加,在电压为33kv时达到最大值;纳米纤维的形貌随着电压增加,直径从528.42nm减小到243.25nm,标准偏差从43.25%减小到28.02%。当通气速度为800ml/min,溶液输入速度为8ml/h,纺丝电压为33kv时,纳米纤维毡的产量达到最大值2.8g/h。     

聚乳酸的静电纺丝行为及其纤维结构研究

用静电纺丝法制备了纤维平均直径为350～1900nm的聚乳酸纤维,用扫描电镜研究了纤维的形貌,并用实验设计方法研究了纺丝工艺参数(溶液浓度、电场电压)对纤维平均直径的影响,同时用差示扫描量热分析和X射线衍射研究了静电纺丝所得纤维的结构.研究结果表明:溶液浓度对纤维的平均直径有较大的影响,溶液浓度较低时易形成珠状结构的纤维,纤维的平均直径随着聚合物浓度的增大而增大,并随电场电压的增大而减小.与浇铸膜相比,静电纺丝所制得的纤维有较低的结晶度,并且结晶结构不够完善.由静电纺丝制备的聚乳酸纳米纤维膜在组织工程和药物缓释等领域有潜在的应用前景.     

静电纺再生丝素纳米纤维:纤维直径分布与力学性能

采用静电纺丝的方法研制了再生丝素纳米纤维(ERSF)膜,纤维直径为50～1000nm.将脱胶后的桑蚕丝溶解在摩尔比为1:2:8 的60℃CaCl2/CH3CH2OH/H2O三元体系中,将该溶液冷冻干燥后溶解在98%的甲酸中得到再生丝素溶液,对其进行静电纺丝.研究了不同纺丝条件下,静电纺再生丝素纤维的直径分布.研究发现:在一定的电压和喷丝头与接收屏的距离(C-D)下,7wt%是具有良好可纺性的临界浓度.纤维的直径随着溶液浓度的增加而增大,随着C-D的增加而减小,并且在C-D较大时可以获得较均匀的纤维.电压是另一个影响纤维直径的重要因素,当电压高于某一数值时,可以纺得细而均匀的纳米级再生丝素纤维.在9wt%,12cm C-D and 15KV 的纺丝条件下,80%的纤维直径在50～150nm之间.由于所纺得的再生丝素纤维膜在水中会产生收缩,因此用甲醇和丙酮对其进行处理.力学性能是影响纤维膜实际使用的重要性能,我们测定和分析了静电纺再生丝素纤维膜处理前后的力学性能.     

基于针尖诱导的静电纺丝实验分析

针尖诱导电纺技术（TIE）利用针尖阵列插入聚合物溶液表面后快速抽离,由于高压强电场和黏性力作用在液面抽离处诱导形成泰勒锥,进而在收集板上得到大量纳米纤维,实现纳米纤维的批量制造．实验结果表明在不同电极间距下,电纺阈值电压随着溶液浓度的增加而增大．当工作电压为63kV,溶液槽尺寸为142mm×50mm时,电纺聚氧化乙烯（PEO）溶液的纤维产量达1．9612g／h．当工作电压从45kV增加到63kV时,纤维沉积均匀性变化范围为31．08％～43．23％．     

溶液喷射法制备间位芳纶纳米纤维的研究

采用溶液喷射纺丝技术制备了间位芳纶(PMIA)纳米纤维,探讨了溶液浓度、气压、挤出速率和接收距离等参数对纤维形貌和直径的影响,结果表明,在溶液浓度为12%(质量分数)、牵伸风压为0.12 MPa、挤出速率为0.8mL/h、接收距离为40cm条件下,所得PMIA纳米纤维形貌较好,纤维平均直径可达276.7nm;采用高速旋转滚筒,制备了PMIA取向纳米纤维,讨论了滚筒转速对PMIA纤维膜性能的影响。结果表明,随着滚筒转速提高,纤维膜取向度及其力学性能均提高,1 300r/min时达到最大值,而膜的孔隙率则随着转速的提高逐渐减小,但仍可达79.7%以上。     

聚芳硫醚砜纳米纤维直径的影响因素及其控制

针对制备条件对聚芳硫醚砜纳米纤维直径大小的影响,文中设计了正交实验,集中考察了溶液浓度、环境温度、应用电压、喷嘴到收集屏的距离和流量五种因素对静电纺丝制备聚芳硫醚砜纳米纤维的影响,结果表明,溶液浓度对纳米纤维直径的影响最大,可通过调整溶液的浓度及黏度来控制所制备的纳米纤维直径。     

动态线纺聚乙烯醇/海藻酸钠纳米纤维膜的制备

为了实现静电纺纳米纤维产量化的制备,使用自主设计的无针式动态线性电极静电纺丝机制备聚乙烯醇(PVA)/海藻酸钠(SA)(AP)纳米纤维膜。采用扫描电子显微镜(SEM)研究PVA/SA配比、收集距离和纺丝电压对纤维形貌及直径分布的影响。结果表明,PVA/SA配比对纤维形貌影响最大,随着SA含量降低,溶液牵伸顺利;在此基础上随着距离增加,纤维形貌逐渐改善但不匀率有所增加。当7.5%PVA与2%SA按体积比9∶1共混时,所得纤维形貌及直径分布最佳,最佳纺丝电压和距离分别为75 kV和25 cm,纤维平均直径为(187±44) nm,产量可达2.5 g/h。为AP纳米纤维膜的规模化制备提供了参考。     

聚-DL/L-丙交酯(30DL/70L)纳米纤维的电纺研究

对生物可吸收聚-DL/L-丙交酯(30DL/70L)体系进行了静电纺丝.研究了聚-DL/L-丙交酯(30DL/70L)的浓度,加料速度,电压,喷头与接收体之间的距离等因素对纤维形态的影响,制备出纳米纤维膜,并用扫描电镜(SEM)等对纤维膜进行表征.结果表明,电纺溶液浓度和溶剂对纤维直径影响比较明显,减小电纺溶液浓度和采用复合溶剂CHCl3/DMF可得到更细的纳米纤维;一定范围内适当的增加电压、减小距离和减小加料速度有利于减小纤维直径.在聚-DL/L-丙交酯(30DL/70L)浓度为5g/100mL溶剂、加料速度1mL/h、喷头与接收体之间的距离6cm、电压15kV电纺条件下,可制备直径50nm左右的聚-DL/L-丙交酯(30DL/70L)纳米纤维膜.     

磁场辅助静电纺有序PAN/PVP复合纳米纤维的制备及工艺优化

磁场辅助静电纺丝(MFAES)技术能够制备有序纳米纤维,但其参数间的匹配关系很少被系统研究。通过MFAES方法制备了有序聚丙烯腈(PAN)/聚乙烯吡咯烷酮(PVP)复合纤维,应用正交实验分析了纺丝中主要的过程参数对复合纤维直径和有序度的影响。实验表明:随着浓度增大,复合纤维的直径增大,得到复合纤维的最小直径为496nm;溶液浓度和纺丝电压是复合纤维有序度的显著影响因素,在溶液浓度为14wt%、PAN/PVP配比为80∶20、纺丝电压为12kV、磁铁间距为2cm时,复合纤维的有序度最高达95%。     

基于近场静电纺丝的微／纳米结构直写技术

基于近场静电纺丝（舾）,研究了可用于柔性电子制造的微／纳米结构直写技术．构建了电极、收集板可协调运动的直写实验平台,分析了电纺丝参数对微／纳米结构直写过程的影响和直写参数间的匹配．通过缩短电纺丝距离实现对直写过程的控制,分别采用直径为25μm的实心探针针尖和内径为232μm的空心注射针尖作为电纺丝喷头,可有序地直写出直径为50—500nm的纳米纤维和线宽为1—8μm的微米结构．实验结果表明：微米结构线宽随收集板速度和PEO溶液浓度的变大而变大;直写工作电压随收集板运动速度的变大而减小,随电极至收集板距离的增加而变大．协调电极与收集板运动速度,平行直写微米结构间距可控制在100-180μm之间．     

Near-field electrospinning

A near-field electrospinning (NFES) process has been developed to deposit solid nanofibers in a direct, continuous, and controllable manner. A tungsten electrode with tip diameter of 25 microm is used to construct nanofibers of 50-500 nm line width on silicon-based collectors while the liquid polymer solution is supplied in a manner analogous to that of a dip pen. The minimum applied bias voltage is 600 V, and minimum electrode-to-collector distance is 500 microm to achieve position controllable deposition. Charged nanofibers can be orderly collected, making NFES a potential tool in direct write nanofabrication for a variety of materials.     

Preparation and luminescent properties of YVO4:Eu3+ nanofibers by electrospinning

This paper describes a procedure based on electrospinning for generating europium-doped yttrium vanadate (YVO4:Eu3+) nanofibers with diameters ranging from 30 to 50 nm. The YVO4:Eu3+ nanofibers were obtained through calcining precursory nanofibers, which were prepared through the electrospinning method. Suitable electrospinning parameters, such as concentration of PVP in solution, spinneret tip-to-collector plate distance (TCD), and applied voltage between spinneret and collector plate, are used to obtain thinner and more uniform precursory nanofibers of YVO4:Eu3+, which is important for preparing smaller diameter pure YVO4:Eu3+ nanofibers. The luminescent properties of the YVO4:Eu3+ nanofibers including excitation and emission spectra and fluorescence lifetime were studied. The excitation spectrum shows a broad band extending from 200 to 350 nm, which corresponds to the strong vanadate absorption in YVO4:Eu3+. The emission spectrum is dominated by the red 5D0 --> 7F2 hypersensitive transition of Eu3+. The fluorescence lifetime of Eu3+ 5D0 --> 7F2 (619 nm) is determined to be 493 micros at room temperature, which is basically in accordance with that in the bulk (521 micros).     

Three-jet electrospinning using a flat spinneret

Electrospinning is a simple but highly versatile technology to produce nanofibers from solutions or melts mostly of polymers using electrostatic forces. A primary challenge facing electrospinning is its low productivity mainly limited by flow rate. In this work, a custom-made three-hole spinneret instead of conventional needles was adopted to enhance the flow rate of electrospinning. Three-jet formation, nanofiber deposition, nanofiber morphology and size were characterized by digital camera and scanning electron microscopy (SEM) as the effects of several governing parameters in electrospinning, including applied voltage from 19.8 to 21.0 kV, working distance from 15.2 to 16.8 cm and flow rate from 6.0 to 9.0 mL/h. It was found that three simultaneous stable jets were ejected from the three-hole spinneret under suitable operating conditions. Moreover, it was found that the fibers collected from the jets from each hole deposited separately in circular spots on a stationary collector. The resultant fibers mostly have an average diameter of less than 300 nm. It has been proved that simple holes on a flat surface can be used to electrospin nanofibers. The three-hole spinneret produces nanofibers at flow rates greater than that in single needle electrospinning. Flow rate has the potential to be easily scaled up by increasing the spinneret diameter and the number of holes.     

High throughput tip-less electrospinning via a circular cylindrical electrode

High throughput production of nanofibers by means of "Tip-less Electrospinning" (TLES) has been demonstrated using a circular cylinder as the emitting electrode. Electrohydrodynamics instabilities on a thin liquid film under high electrical field can generate artificial liquid jets for the TLES process. Experimental results have shown that the yield of poly(ethylene oxide) nanofibers can be more than 260 times in weight as compared with a single-jet electrospinning process. Parameters affecting the TLES process including applied voltage, polymer solution concentration, electrode-to-substrate distance and the thickness of liquid films have been characterized. As such, TLES has potential for high-throughput, massive production of electrospun nanofibers.     

Electric field analysis of spinneret design for multihole electrospinning system

Electric field plays a key role in producing required nanofibers in electrospinning. This study aims to improve the electric field distribution of the multijet spinning system by designing the spinneret configuration. A novel 19-hole multistep electrospinning configuration is presented. The simulation results show that the electric field strength at the central position is intensified due to the protuberant step on the spinneret, and therefore more uniform electric field is obtained compared with the 19-hole flat spinneret. We demonstrate that the multistep spinneret configuration produces finer fibers and more continuous fiber mats compared with the flat spinneret configuration because of the improved electric field distribution. Jet repulsion in the multijet electrospinning process is studied. It is found that the electric field line distribution, which is determined by the spinneret configuration, plays a dominant role in influencing jet repulsion. Applied voltage is the main factor responsible for jet repulsion for a given spinneret configuration.     

Needle-disk electrospinning inspired by natural point discharge

Point discharge is a natural phenomenon which principle and application are both under active investigation. In this work, a needle-disk electrode spinneret was designed through the combination of the point discharge concept and the merits of typical needleless electrospinning (disk as spinneret). The desired outcome for point electrode system is to produce a controllable process of jet formation, with respect to the control of jet site and amount of jets under a lower applied voltage value. Two comparisons were used: (i) in comparison to the typical needleless electrospinning method (disk electrospinning), the needle-disk electrospinning produce finer and more uniform nanofibers. Further numerical simulation results confirmed that the needle-disk electrode induced electric field intensity which is 5.33 times higher than that of disk electrode under the same parameters; (ii) both the numerical simulation and experimental results showed that needle-disk electrospinning can produce competitive quality of nanofibers accompanied by enhanced throughput, compared with the traditional single-needle electrospinning method. Finally, we demonstrate that needle-disk electrospinning produces nanofiber with super-high throughput of 13.5 g/h, which is 183 times higher than traditional electrospinning under similar spinning conditions.     

静电纺羧甲基壳聚糖纳米纤维直径的预测模型

目的研究羧甲基壳聚糖溶液浓度和静电纺丝工艺参数对纳米纤维直径的影响。方法按照静电纺丝的原理,选取溶液浓度、电压、流量和喷头直径等4个影响因素,使用响应面法中的Box-Behnken设计对羧甲基壳聚糖静电纺丝纤维直径进行预测,得到二次多元回归模型。结果羧甲基壳聚糖溶液浓度、流量、浓度的二次项和喷头直径的二次项对纤维直径影响显著,该模型实验值与预测值高度拟合。结论通过响应面得到的模型能预测羧甲基壳聚糖纤维的直径,同时明确了羧甲基壳聚糖纤维的最佳电纺参数。