聚乳酸/聚乙烯醇纳米纤维的制备及结构

以二甲基亚砜为溶剂,制备不同配比的聚乳酸(PLLA)和聚乙烯醇(PVA)的混合溶液,静电纺丝制得PLLA/PVA纳米纤维。采用红外光谱仪、原子力显微镜等对PLLA/PVA纳米纤维结构与性能进行了表征。结果表明:PLLA/PVA纳米纤维中PVA上的羟基与PLLA上的羰基形成了氢键,PLLA与PVA之间存在一定的相互作用,但PLLA/PVA纳米纤维存在相分离现象;混合溶液的PLLA质量分数为11%,PVA质量分数为8%时可以得到较好的PLLA/PVA纳米纤维,但PVA质量分数为6%时出现液滴及珠丝,PVA质量分数为4%时,不能制得纳米纤维。     

On the electrospinning of poly(vinyl alcohol) nanofiber mats: A revisit

Electrospinning was used to fabricate mats of poly(vinyl alcohol) (PVA; M_w = 72,000 Da, degree of hydrolysis ≈ 97.5–99.5) nanofibers from PVA solutions in reverse osmotic water. The effects of solution concentration, applied electrical potential, sonication, and collection distance on morphological appearance and diameters of the as‐spun fiber mats as well as those of the individual fibers were carefully investigated mainly by scanning electron microscopy. The effect of the distance from the center of the as‐spun fiber mat on morphological appearance and diameters of the as‐spun fibers was also investigated. The mechanical integrity of some as‐spun PVA fiber mats was also investigated. At all concentrations and applied electrical potentials investigated, the average diameters of the as‐spun PVA fibers ranged between 85 and 647 nm. The use of sonication to prepare a PVA solution caused the viscosity of the solution to decrease; hence, the observed decrease in the average diameters of the as‐spun fibers and the average diameters of the as‐spun fibers were practically the same throughout the as‐spun fiber mat. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

含氯化钠的聚乙烯醇静电纺丝研究

研究了不同聚合度聚乙烯醇与少量氯化钠盐混合物水溶液的静电纺丝,并与单纯聚乙烯醇水溶液的静电纺丝进行了对比。利用扫描电镜观察纤维的形态、直径变化。结果表明:聚乙烯醇水溶液中加入少量氯化钠,由于离子的作用可以使喷射流表面电荷密度增大,静电纺丝可得到比单纯聚乙烯醇更细的纳米纤维。     

Antibacterial electrospun chitosan/poly(vinyl alcohol) nanofibers containing silver nitrate and titanium dioxide

Chitosan/poly(vinyl alcohol) (PVA) nanofibers with antibacterial activity were prepared by the electrospinning of a chitosan/PVA solution with a small amount of silver nitrate (AgNO₃) and titanium dioxide (TiO₂). Nanofibers with diameters of 270–360 nm were obtained. The yield of low‐viscosity chitosan (LCS)/PVA nanofibers was higher than that of high‐viscosity chitosan (HCS)/PVA, and the water content of the HCS/PVA nanofibers and the LCS/PVA nanofibers were 430 and 390%, respectively. The nanofibers developed in this study exhibited antibacterial activities of 99 and 98% against Staphylococcus aureus and Escherichia coli, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Microstructure and characterization of electrospun poly(vinyl alcohol) nanofiber scaffolds filled with graphene nanosheets

Graphene nanosheets (GNSs) have attracted significant scientific attention because of their remarkable features, including exceptional electron transport, excellent mechanical properties, high surface area, and antibacterial functions. Poly(vinyl alcohol) (PVA) solutions filled with GNSs were prepared for electrospinning, and their spinnability was correlated with their solution properties. The effects of GNS addition on solution rheology and conductivity were investigated. The as‐spun fibers were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC). The results revealed the effects of GNS on the microstructure, morphology, and crystallization properties of PVA/GNS composite nanofibers. The addition of GNSs in PVA solution increased the viscosity and conductivity of the solution. The electrospun fiber diameter of the PVA/GNS composite nanofiber was smaller than that of neat PVA nanofiber. GNSs were not only embedded at the fibers but also formed protrusions on the fibers. In addition, the crystallinity of PVA/GNS fiber decreased with higher GNS content. The possible application of PVA/GNS fibers in tissue engineering was also evaluated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41891.     

Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite nanofiber mats

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT) nanofiber mats have been fabricated by the electrospinning technique. The PVA/MMT nanofiber mats were characterized by X‐ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and mechanical measurements. The study showed that the introduction of MMT results in improvement in tensile strength, and thermal stability of the PVA matrix. XRD patterns and SEM micrographs suggest the coexistence of exfoliated MMT layers over the studied MMT contents. FTIR revealed that there might be possible interaction occurred between the MMT clay and PVA matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of poly(vinyl alcohol) nanofiber mats crosslinked with blocked isocyanate prepolymer

Poly(vinyl alcohol) (PVA) nanofibers crosslinked with blocked isocyanate prepolymer (BIP) were successfully prepared using the electrospinning process and subsequent thermal treatment. Fourier transform infrared spectroscopy and solid‐state ¹³C NMR spectroscopy demonstrated that chemical crosslinks between the hydroxyl group of PVA and the isocyanate group of BIP were formed. Thermogravimetric analysis and differential scanning calorimetry results indicated that when the BIP content was increased, the thermal stability of PVA/BIP nanofibers increased, and the crystallinity of PVA decreased. Field emission scanning electron microscopy was used to measure the average diameter (200–300 nm) of the electrospun PVA/BIP nanofibers. The water contact angles were 10.2° and 113° for the pristine PVA nanofibers and PVA nanofibers crosslinked with 8 wt% BIP, respectively. The tensile strength of the crosslinked PVA nanofibers was 53.7 MPa, which was seven times higher than that of pristine PVA. The improved tensile strength and water resistance of the crosslinked PVA/BIP nanofibers were due to a combination of increased crosslinking density and decrease in the number of hydroxyl groups on the surface of the PVA/BIP nanofibers. Copyright © 2010 Society of Chemical Industry     

Reactive electrospinning of poly(vinyl alcohol) nanofibers

We aim to couple the electrospinning in‐line with solution chemistry to fabricate novel crosslinked polymer nanofibers. Poly(vinyl alcohol) (PVA) was used as a model polymer due to its high amount of hydroxyl groups. To obtain ideal parameters for electrospinning, pure PVA was explored primarily. To gain crosslinked fibers, PVA was first crosslinked partially with glutaraldehyde (GA) followed by transferring this precursor to a long hot tube which was used as reactor and then electrospun right before gelation. The preheating time and tube‐passing time were determined with viscometer and rheometer. The reactive as‐spun fibers could maintain their original morphology after water immersion due to their high crosslinking degree. The thermal stability and mechanical property of reactive as‐spun fibers were improved drastically compared with pure and GA vapor crosslinked PVA fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of the tacticities of poly(vinyl alcohol) on the structure and morphology of poly(vinyl alcohol) nanowebs prepared by electrospinning

The effects of tacticities on the characteristics of poly(vinyl alcohol) (PVA) nanowebs prepared by an electrospinning technique were investigated. PVA webs composed of uniform nanofibers with syndiotactic dyad (s‐dyad) contents of 53.5 and 57.3% were successfully obtained with electrospinning. By changing processing parameters such as the initial polymer concentration, applied voltage, and tip‐to‐collector distance, we found suitable conditions for forming PVA webs with uniform nanofibers. PVAs of higher s‐dyad contents were prepared at a lower solution concentration and at a higher applied voltage because of the easy formation of syndiotactic PVA chain entanglements at a very low polymer concentration. The average diameter of the nanofibers in a PVA web with the higher s‐dyad content of 57.3% (ca. 240 nm) was thinner than that of the nanofibers in a PVA web with the lowers‐dyad content of 53.5% (ca. 270 nm). In addition, the crystallinity and thermal stability were greatly increased with an increase in the s‐dyad content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electrospinning fabrication and characterization of poly(vinyl alcohol)/waterborne polyurethane nanofiber membranes in aqueous solution

Poly(vinyl alcohol) (PVA)/waterborne polyurethane (WBPU) nanofiber mats were prepared using electrospinning method with aqueous solutions. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermal gravimetric analyzer (TGA), and tensile strength testing machine (ZWICK) were used to characterize the morphology and properties of the PVA/WBPU nanofiber mats. The results showed that the morphologies of PVA/WBPU nanofiber mats changed with the total solid concentration and the mass ratio of PVA/WBPU in the spinning solution. The tensile strength and thermal stability of the fibers could be significantly affected by the WBPU contents. The electrospun PVA/WBPU membranes showed higher water uptake, which would have potential applications in wound dressings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of poly(vinyl alcohol)-clay nanocomposite materials

A series of polymer-clay nanocomposite (PCN) materials that consist of poly(vinyl alcohol) (PVA) and layered montmorillonite (MMT) clay are prepared by effectively dispersing the inorganic nanolayers of MMT clay in organic PVA matrix via an in situ free radical polymerization with AIBN as initiator. Organic vinyl acetate monomers are first intercalated into the interlayer regions of organophilic clay hosts and followed by a one-step free radical polymerization. The prepared poly(vinyl acetate)-clay (PVAc-clay) solution are then saponified via direct-hydrolysis with NaOH solution to form PVA-clay nanocomposite materials. The as-synthesized PCN materials are typically characterized by Fourier-Transformation infrared (FTIR) spectroscopy, wide-angle X-ray diffraction and transmission electron microscopy.The molecular weights of poly(vinyl alcohol) (PVA) extracted from polymer-clay nanocomposite (PCN) materials and bulk PVA are determined by gel permeation chromatography (GPC) analysis with THF as eluant. The viscosity property of PCN materials with different feeding amount of MMT clay is studied by an ubbelohode capillary viscometer. The morphological image of as-synthesized materials is studied by scanning electron microscopy (SEM) and optical polarizing microscope (OPM). Effects of the material composition on the thermal stability, mechanical strength, optical clarity of PVA along with a series of PCN materials, in the form of fine powder and free-standing film, are also studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and UV-visible transmission spectra, respectively.     

二氧化钛光触媒在金属镀膜与金属防护技术中的应用第一部分光触媒分散技术

介绍了二氧化钛的晶体类型和基本性质、典型的锐钛型二氧化钛的XRD图谱。对纳米粒子的团聚现象进行了解释。对纳米粒子的分散原理——高分子分散剂／界面活性剂分散和电解质分散进行了说明。分别介绍了水溶液中二氧化钛以及改性后的锐钛型纳米二氧化钛的Zeta电位与pH的关系。研究了锐钛型纳米二氧化钛在聚丙烯酸盐分散介质中的粒径分布。结果表明,在此分散介质中,纳米颗粒的分布比较集中,粒径小于50．7 nm的粒子占60％,其平均粒径远低于传统的涂料级和颜料级分散的粒子;该溶液呈现明显的丁达尔现象,光触媒活性高,在实验室存放24个月后质量稳定;将此溶胶涂至玻璃表面,所得涂膜透明度高。     

丝素-聚乙烯醇共混溶液静电纺丝及其含银纳米纤维形态研究

研究了不同丝素-聚乙烯醇（SF-PVA）配比的共混溶液和加入硝酸银的丝素-聚乙烯醇（SF-PVA）共混溶液的静电纺丝,利用扫描电镜观察纤维的形态变化。结果表明：在丝素（SF）或聚乙烯醇（PVA）占绝大部分时,整个体系溶解性保持相对稳定,容易形成比较均一的溶液,且纺丝后纤维形态比较均匀、规则;而在两组分含量接近时整个体系的溶解性能较差,不易形成比较均一的溶液,表现为溶液粘度的显著增大,纺丝后纤维不均匀、不规则。笔者选用SF/PVA=1：9（质量比）的共混纺丝液加入硝酸银,随着硝酸银在溶液中含量的增加,溶液电导率会明显增加,纤维的直径明显下降;但随着电导率的增大,纤维中珠状物会增多,纤维均一性也变差。     

熔盐法处理富钛渣制备金红石型TiO_2

工业生产钛白粉的方法主要有硫酸法和氯化法两种,但这两种方法都存在环境污染严重的问题。本文提出了一种常压、低温下钠碱熔盐分解富钛渣制备金红石型二氧化钛的新工艺,从生产源头消除了对环境的污染,实现钛资源的可持续发展。介绍了该反应的制备、水洗、固相离子交换-水解耦合和煅烧过程。实验结果表明,该工艺可以制得理想的金红石型二氧化钛,二氧化钛含量为96.66%。     

深还原钛渣硫酸法制取钛白实验研究

以含钛铁精矿直接还原冶炼的含钛物料（深还原钛渣）为原料,对硫酸法制取颜料级钛白粉的工艺进行了研究。实验结果表明,深还原钛渣具有良好的酸解性能,酸解率可达97%;酸解后得到的钛液过滤性能好;但酸解钛液中氧化镁和氧化铝浓度过高,所以直接以该钛液为原料制得的钛白颜料性能差。采用深还原钛渣和钛精矿按一定比例混合酸解,可以避免钛液杂质含量过高对最终钛白产品质量造成的影响。深还原钛渣较佳用量为不高于钛原料总质量的20%。     

Conjugate electrospinning of continuous nanofiber yarn of poly(L‐lactide)/nanotricalcium phosphate nanocomposite

The continuous nanofiber yarns of poly(L ‐lactide) (PLLA)/nano‐β‐tricalcium phosphate (n‐TCP) composite are prepared from oppositely charged electrospun nanofibers by conjugate electrospinning with coupled spinnerets. The morphology and mechanical properties of PLLA/n‐TCP nanofiber yarns are characterized by scanning electron microscope, transmission electron microscope, and electronic fiber strength tester. The results show that PLLA/n‐TCP nanofibers are aligned well along the longitudinal axis of the yarn, and the concentration of PLLA plays a significant role on the diameter of the nanofibers. The thicker yarn of PLLA/n‐TCP composite with the weight ratio of 10/1 has been produced by multiple conjugate electrospinning using three pairs of spinnerets, and the yarn has tensile strength of 0.31cN/dtex. A preliminary study of cell biocompatibility suggests that PLLA/n‐TCP nanofiber yarns may be useable scaffold materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthesis of poly(vinyl alcohol) derivatives containing amidoxime groups

The modification reaction of poly(vinyl alcohol) (PVAL) with acrylonitrile in alkaline medium was studied. The structure of the resulting polymers was determined by means of IR, ¹H and ¹³C NMR spectroscopy. The influence of solvent composition, catalyst and temperature was evaluated. ¹³C NMR spectroscopy was used for the determination of the sequence distribution of cyanoethylated PVAL (considered as a vinyl alcohol (VAL)-(2-cyanoethyl) vinyl ether (VCE) copolymer). The ¹³C NMR spectra of the methylene carbons in the main chain show three split peaks, the intensities of which change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that VCE units have an alternating tendency in the copolymer. Nitrile groups in cyanoethylated PVAL were converted to amidoxime groups by reaction with hydroxylamine. The reaction showed second order kinetics. The activation energy was found to be 51.6 kJ/mol. Soluble polymeric chelates between amidoximated PVAL and cupric ions have been prepared. It is noteworthy that not all the amidoxime groups participate in binding cupric ions.     

Electrospinning preparation,characterization, and enhanced photocatalytic activity of an Silicotungstic acid (H4SiW12O40)/poly(vinyl alcohol)/poly(methyl methacrylate) composite nanofiber membrane

Silicotungstic acid (H₄SiW₁₂O₄₀)/poly(vinyl alcohol) (PVA)/poly(methyl methacrylate) (PMMA) composite nanofiber membranes were prepared by an electrospinning technique. A PMMA emulsion was mixed with PVA and H₄SiW₁₂O₄₀ evenly in water (electrospinning solvent). The configuration and elemental composition of the membranes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy. The results indicate that H₄SiW₁₂O₄₀ with an intact Keggin structure existed in the composite membrane. The as‐prepared H₄SiW₁₂O₄₀/PVA/PMMA membranes exhibited enhanced photocatalytic efficiency (>84%) in the degradation of methyl orange (MO); it outperformed H₄SiW₁₂O₄₀ powder (4.6%) and the H₄SiW₁₂O₄₀/PVA nanofiber membrane (75.2%) under UV irradiation. More importantly, the H₄SiW₁₂O₄₀/PVA/PMMA membranes could be easily separated from the aqueous MO solution, and the photocatalytic efficiency of the membranes decreased inappreciably after three photocatalytic cycles. This may have been due to the enhanced water tolerance of the membranes and the stability of H₄SiW₁₂O₄₀ in the membranes. The photocatalytic process was driven by the reductive pathway with a much faster degradation rate because of the presence of PVA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43193.     

A study on UV-protection property of poly(vinyl alcohol)-montmorillonite composite nanofibers

The aim of this research is to investigate the possibility of barrier effect of poly(vinyl alcohol) (PVA)/montmorillonite (MMT) nanofiber, against the UV radiation in different electrospinning situations. For this purpose, nanofibers with different weight ratio of PVA and nanoclay (MMT) were electrospun under different circumstances, and the amount of protect that is created by the nanofiber web against UV radiation by examining the rate of degradation of methylene blue dye that was protected by the same web was estimated. The UV-vis spectrometry was used for the analysis of methylene blue color. In order to investigate the morphology and miscibility of PVA-MMT composite nanofiber, X-ray diffraction, scanning election microscope, and Fourier transform infrared spectrometer have been used. Thermal gravimetric analysis is used to investigate and explore how nanofibers behave against heat.