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1.
Using poly(vinyl alcohol) (PVA) and perfluorslulfonic acid (PFSA) as coating materials, poly(acrylonitrile) (PAN) hollow fiber ultrafiltration membrane as substrate, PVA-PFSA/PAN composite membranes were fabricated by dip-coating method. The fabricated composite membranes were used to the separation of dimethyl carbonate (DMC)/methanol (MeOH) binary mixtures by pervaporation process. SEM images verify that the coated layer is well combined with substrate and the thickness nearly linearly increases with the coating solution concentration. The separation factor increases but at cost of the decline of permeation flux when the concentration of the coating solution or its PVA mass fraction increase. The permeation flux increases and separation factor slightly increases with the feed temperature increasing at 30–60 °C. The increase of feed MeOH concentration leads to an improvement of permeation flux and a decline of separation factor.  相似文献   

2.
The influences of the insecticides quinalphos, chlorpyriphos, methyl parathion, endosulfan, imidacloprid and deltamethrin applied three times at 10 days intervals at half of their recommended field concentrations to potted plants of a planthopper-susceptible and a planthopper-resistant rice variety, on reproduction and survival of whitebacked planthopper, Sogatella furcifera (Horvath), and on the chemistry of its host plant, were investigated. Methyl parathion, deltamethrin and quinalphos enhanced the fecundity of the hopper (164-211 vs. 131 for the control) and consequently the resurgence ratio (increased up to 1.75 fold). Methyl parathion and deltamethrin significantly increased nymphal survival (59.3 vs. 52.2% for the control) and the growth index (4.8 vs. 4.2 for the control) of the hopper. The sex ratios of adults emerging on methyl parathion- and deltamethrin-treated rice plants increased in favour of females (1.51 vs. 1.15 for the control) on the susceptible variety but was not altered on the resistant variety. Biochemical analyses of the rice leaves revealed significantly higher quantities of reducing sugars, proteins and amino acids, but lower amounts of total phenols in leaf sheaths and blades of methyl parathion-, deltamethrin- and quinalphos-treated plants of the two varieties. The leaf sheaths and blades of the resistant variety contained more than twice the total phenols present in those of the susceptible variety. The results showed a positive correlation between increased levels of reducing sugars, amino acids and proteins in the rice plants and the fecundity of S. furcifera and a negative correlation between phenol contents of the rice plants and fecundity.  相似文献   

3.
Porous polyacrylonitrile (PAN) fiber mat was prepared by electrospinning PAN in N,N-dimethylformide solution with poly(methyl methacrylate) (PMMA) as pore-forming agent. Then, the porous PAN fiber mat was chemical modified by the tetraethylenepentamine to acquire aminated porous polyacrylonitrile (APPAN) fiber mat. Common aminated PAN fiber mat was also prepared for comparison. The surface morphologies of the APPAN and PAN fiber mat were characterized by scanning electron microscopy (SEM) and the corresponding specific surface areas were also measured. FT-IR/ATR spectra of the APPAN and PAN fiber mat were recorded for analysis of the surface chemical structures. The Cr(VI) absorption results demonstrated that the porous structure in the fiber could obviously increase the absorption capacity of the fiber mat.  相似文献   

4.
Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20–30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 cm−1 shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.  相似文献   

5.
Electrical conductive nanocomposite fibers were prepared with polyaniline (PANI), polyacrylonitrile (PAN) and multi-walled carbon nanotubes (MWCNTs) via electrospinning. The morphology and electrical conductivity of the PANI/PAN/MWCNTs nanocomposite fibers were characterized by scanning electron microscope (SEM) and Van De Pauw method. Electrical conductivity of nanocomposite fibers increased from 1.79 S·m?1 to 7.97 S·m?1 with increasing the MWCNTs content from 3.0 wt% to 7.0 wt%. Compared with PANI/PAN membranes, the mechanical property of PANI/PAN/MWCNTs nanocomposites fiber membranes decreased. The microwave absorption performance of composite films was analyzed using waveguide tube, which indicated that with the thickness increasing the value of RL reduced from ?4.6 to ?5.9 dB.  相似文献   

6.
Acrylonitrile-methyl itaconate (AN-MIA) copolymers were successfully prepared by free-radical solution copolymerization, and then were spun into precursors of carbon fibers by one-step wet-spun method in this study. Effect of methyl itaconate(MIA), itaconic acid (IA) and methyl acrylate (MA) on the characteristics of the copolymers and precursors were studied in contrast. The monomer reactivity ratios for AN/MIA system were determined by Kelen-Tudos (K-T) method with r 1=0.65, r 2=1.80. The viscosity test shows that using MIA as a co-monomer is an effective way to decrease the viscosity of PAN solution. During the spinning and stretching processes, polyacrylonitrile (PAN) copolymer with MIA as co-monomer can reach the higher total draw-ratio of 12.0 folds, while PAN copolymer with IA as co-monomer can reach only 8.5 folds. The fineness and elongation at-break of the PAN precursors with MIA as co-monomer improve, but the tenacity decreases. DSC test shows MIA is less effective in improving the thermal property than IA.  相似文献   

7.
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   

8.
Polymer organic-inorganic hybrid nanofibers constitute a new class of materials in which the polymeric nanofibers are reinforced by uniformly dispersed inorganic particles having at least one dimension in nanometer-scale. In the present study, polyacrylonitrile (PAN) and PAN/Na-montmorillonite (PAN/Na-MMT) nanofibers were conducted via electrospinning process. Electrospun PAN and PAN/Na-MMT fibers with the respective mean fiber diameter of about 220 and 160 nm were prepared. The influence of the clay-montmorillonite on the morphology and diameter of nanofibers was investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. The microscopic techniques propose that the PAN/Na-MMT composite nanofibers show lower mean fiber diameter than the neat PAN nanofibers. Besides, the difference in nanoclay-content has a slight effect on the distribution of fibers diameter. Thermogravimetric analysis (TGA) results suggest that introduction of clay-nanomaterials improves the thermal characteristics of fibers.  相似文献   

9.
Porous PLA fibrous membranes with different morphologies were successfully fabricated by varying the relative humidity. When the relative humidity was higher than 45 %, nanopores morphology appeared on the surface of PLA fibers. The micro-structures of PLA fibers and the packing densities and through-pore sizes of the PLA fibrous membranes were measured and found to greatly influence the smoke adsorption properties. The smoke adsorption was recorded in photos, and the process of how smoke adsorbed on the membranes was observed by SEM. The max removal efficiencies of nicotine, tar, water vapor, and carbon monoxide were 40.0 %, 36.9 %, 5.8 % and 13.6 % measured by a cigarette-smoking machine, and sensory evaluation was conducted to assess the practical application of fibrous membranes for smoke adsorption.  相似文献   

10.
Polyacrylonitrile (PAN) nanoparticles were successfully prepared by dispersion polymerization of acrylonitrile (AN) in water using 10 and 20 wt% of the poly(ethylene oxide)-b-PAN macromolecular RAFT (PEO-b-PAN macro-RAFT) agent (M n=5,600 g/mol, PDI=1.15). The degrees of polymerization of the PEO and PAN blocks were 113 and 16, respectively. The PAN nanoparticles had a crumpled spherical appearance and their sizes ranged from 50–80 nm. The degree of crystallinity of the PAN particles was 23 %. The M n values of the PAN nanoparticles prepared with 10 and 20 wt% of the PEO-b-PAN macro-RAFT agent were 33,900 and 25,800 g/mol, respectively. The existence of the PEO block on the surface of the PAN nanoparticles was confirmed by 1H NMR spectroscopy and XPS.  相似文献   

11.
本研究通过对木薯根系分泌物进行提取、分离与鉴定,探究不同木薯品种根系分泌物的差异,为筛选抗化感耐连作木薯新种质提供参考。以木薯组培苗琼脂培养基为试验材料,采用正交试验设计,结合GC-MS技术考察不同萃取材料和洗脱剂对木薯根系分泌物的提取和分离效果,选择最优方案测定‘新选048’‘南植199’和‘华南205’的根系分泌物。结果表明：（1）木薯根系分泌物水溶性物质提取的最优方案为：用去离子水超声提取捣碎的琼脂培养基30 min,固液分离后用XAD-2萃取、无水乙醇洗脱,浓缩后用GC-MS检测,成功鉴定出包括有机酸类、醇类、酯类、酮类、醛类等26种有机化合物。（2）醇溶性物质提取的最优方案为：用50%乙醇超声提取捣碎的琼脂培养基30 min,固液分离后用XAD-4萃取、无水乙醇洗脱,浓缩后用GC-MS检测,鉴定出包括有机酸类、醚类、酯类、酮类、醛类等15种有机化合物。（3）不同品种根系分泌物的水溶性和醇溶性成分均有差异。‘南植199’根系分泌物的主要水溶性物质有羟乙酸甲酯（相对含量为3.72%）、羟基丙酮（2.40%）、甲肼（1.79%）等,主要醇溶性物质有乙醇醛（18.89%）、羟基丙酮（2.47%）、甲酸（2.25%）等;‘新选048’的主要水溶性物质有甲酸（2.68%）、1,5-戊二醇（2.39%）、丙烯酸羟乙酯（2.01%）等,主要醇溶性物质有乙醇醛（17.00%）、甲酸（2.62%）、羟基丙酮（2.46%）等;‘华南205’的主要水溶性物质有甲酸（2.23%）、羟基丙酮（1.80%）、羟乙酸甲酯（1.43%）等,主要醇溶性物质有乙醇醛（16.58%）、甲酸（3.06%）、八氟戊醇（2.98%）等。不同木薯品种的根系分泌物种类和含量均有差异,从而导致其抗化感耐连作能力的差异,为筛选耐连作品种缓解木薯连作障碍成为可能。  相似文献   

12.
A series of PU fibrous membranes were fabricated by using electrospinning method. The microstructure of the membranes was characterized by field-emission scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectrum. Their mechanical properties were tested by dynamic mechanical thermal analysis and stress-strain behaviors. The solution concentration, the applied voltage and the tip-collector distance had an effect on the crystallinity degree and molecular orientation of PU, the size and distribution of the fiber diameter and the point-bonded structures between the fibers, leading to the change in the microstructure and the mechanical properties of the fibrous membrane. Fibers with a smaller diameter had higher strength but lower ductility. The fibrous membranes indicated the similar stress-strain behaviors, which slopes in the initial stage were low and that in the later stage were high. The initial elastic behavior with the low Young’s modulus were attributed to the network structure of the fibrous membranes and that with the high Young’s modulus was from the electrospun PU fibers.  相似文献   

13.
This paper presents new mixed-matrix membranes (MMMs) synthesized via incorporating hexamethylenetetramine dicyanamide cadmium nanoparticles, a metal organic framework (MOF), into the polysulfone (PSF) matrix. The MMMs are characterized using FTIR and SEM analyses, and their gas permeation properties are evaluated at different MOF loadings and various pressures. The results show that the nanoparticle is compatible with the polymer and distributes homogenously in the matrix. Compared to the pristine PSF membrane, the MMM with 2.5 wt. % of the MOF nanoparticles has lower CO2, CH4, N2 and O2 permeabilities but significantly higher CO2/CH4, CO2/N2 and O2/N2 gas pair selectivities (i.e., 41.66, 20.08 and 5.09, respectively, which are 42.6, 61.6 and 60.02 % higher). As the total pressure increases, the gas permeabilities of the pristine PSF membrane and the MMMs decrease, but their sieving abilities increase. These results suggest that gas selectivities of high free-volume polymers with poor sieving abilities can be improved by incorporating the MOF into the polymer.  相似文献   

14.
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   

15.
Ployacrylonitrile (PAN) nanofibers were formed by electrospinning. Amidoxime ployacrylonitrile (AOPAN) nanofibers were prepared by reaction with hydroxylamine hydrochloride, which were used as the matrix for metal ions chelation. FTIR spectra of the PAN nanofibers and AOPAN nanofibers were recorded for analysis of the surface chemical structures. The AOPAN conventional fibers were also prepared for comparison, and surface morphologies of the modified PAN conventional fibers and PAN nanofibers were observed by FESEM. Metal ions concentrations were calculated by AAS. The chelated isothermal process and kinetics parameters of the modified PAN nanofibers and PAN conventional fibers were studied in this work. Results indicated that the saturated coordinate capacity of AOPAN nanofibers to Cu2+, Cd2+ was 3.4482 and 4.5408 mmol/g (dry fiber) respectively, nearly two times higher than that of AOPAN conventional fibers. Besides, the desorption rate of Cu2+ and Cd2+ from metal chelated AOPAN nanofibers was 87 and 92 % respectively in 1 mol/l nitric acid solution for 60 min. The isothermal processes were found to be in conformity with Langmuir model.  相似文献   

16.
橡胶粒子膜蛋白双向电泳体系的建立和质谱初步分析   总被引：6，自引：0，他引：6  
橡胶粒子是橡胶树乳管细胞中进行橡胶生物合成的一种特殊细胞器。参与橡胶生物合成的橡胶转移酶、橡胶延长因子等重要酶类和相关的蛋白质调控因子均定位于橡胶粒子的表面或镶嵌于橡胶粒子膜中。本研究在SDS-PAGE分离橡胶粒子膜蛋白的基础上,使用pH3￣10非线性IPG胶条进行2-DE双向电泳,成功地分离了橡胶粒子膜蛋白,在2-DE银染胶上共得到约520个蛋白质点,并通过基质辅助激光解吸附飞行质谱(MALDI-TOF)对部分蛋白质点进行了初步分析鉴定。检索蛋白质数据库证明其中的蛋白质点包括橡胶延长因子(REF)和橡胶过敏蛋白Hev3等典型的橡胶粒子膜蛋白,另外还有一些功能未知的蛋白质。从银染2-DE胶上可以看出,REF在橡胶粒子膜蛋白中占有很大的比例,这表明REF在橡胶生物合成中可能具有非常重要的作用。通过比较蛋白质组学研究发现,橡胶粒子膜上存在乙烯和茉莉酸信号响应蛋白。乙烯和茉莉酸对橡胶生物合成的调控作用可能与橡胶粒子膜上存在它们的响应蛋白有关。橡胶粒子膜蛋白2-DE双向电泳体系的建立为全面研究橡胶粒子膜蛋白的组成及其变化奠定了基础。  相似文献   

17.
Carbon fibers and precursor polyacrylonitrile (PAN) fibres that contain either silica or hydroxyapatite particles, imbedded during the spinning process, were studied in this paper. The modified PAN fibers were thermally stabilized using a multi-stage process in the temperature range between 150 to 280 °C in an oxidative environment. Subsequent carbonization leading to obtain carbon fibers was carried on at 1000 °C in an argon atmosphere. The changes of properties of composite precursor fibers taking place during stabilization and carbonization processes were investigated by the combination of Differential Scanning Calorimetry, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy equipped with energy dispersive X-ray spectrometer and ultrasonic methods. Mechanical properties, such as tensile strength, static Young’s modulus, elongation at fracture were analyzed at each stage of thermal stabilization process. Additionally some traditional measurements like fiber diameter and mass were studied. Ceramic powders added to the spinning solution were present also in composites fibers after stabilization and carbonization process. Such modification allows to avoid the post-treatment operations, for example by coating or covering with films, which were usually necessary in order to obtain bioactive character of implants. Modification of carbon fibers using calcium phosphate or silica can lead to the development of a new materials for the manufacturing of implants which can establish direct chemical bonds with bone tissue after implantation.  相似文献   

18.
《Crop Protection》1988,7(3):168-176
Between 1982 and 1984, the Nicaraguan Ministry of Agricultural Development and Agrarian Reform (MIDINRA) used an area-wide network of trap crops of cotton from February to August to suppress boll weevils (Anthonomus grandis Boheman) on 17450 ha (1982–1983) and 35 200 ha (1983–1984) of cotton land in the Leon region of Nicaragua. In the 1982–1983 season the programme reduced boll weevil infestations (expressed as weevil-days) 89% in Zone II (normal rainfall area) when compared with untreated controls. This suppression of adult weevils resulted in a reduction from 18 to 10 seasonal applications of methyl parathion for weevil control. The programme reduced weevil insecticide costs per kg of raw cotton produced by an area-wide average of 43%. In the 1983–1984 season the programme reduced weevil-days by an area-wide 36% in commercial fields. In Zone II, trap cropping reduced by 40% the quantity of insecticides applied for weevil control. Weevil control costs per kg of raw cotton produced were reduced by 44%. Non-significant cost reductions for weevil control in Zone I may have been due to early drought, cattle grazing on trap crop areas, or inadequate management of trap crops. The 2-year programme was the largest mobilization of public and private resources for pest management ever undertaken in Nicaragua, and gives practical evidence that suppression of between-season boll weevil populations can form the basis for more profitable control of this key pest in the commercial cotton season.  相似文献   

19.
Polyacrylonitrile (PAN) oriented nanofibers were produced by homemade needleless electrospinning device. Spiral coils were adopted to replace the traditional spinning needles in this equipment. The tracks of multi-jets were controlled by adjusting the microcurrent during the eletrospinning process. The microcurrent value and the motion track of the spinning jet during the spinning process were observed, the fiber morphology and the mechanical properties of fiber membranes were measured. The results revealed that the average diameters of the electrospun fibers were increased from 490 nm to 740 nm. with the addition of organic salt. Meanwhile, the self-clustering phenomenon was obviously observed, and the mechanical properties of obtained fibers were also altered, the tensile strength was improved from 3.63 MPa to 23.90 MPa, while the strain decreased from 74.6 % to 27.1 %.  相似文献   

20.
The present study is focused on studying the swelling kinetics, thermal and aqueous stabilities, and determination of various forms of water in the chitosan (CS) and polyacrylonitrile (PAN) blend and semi-interpenetrating polymer network (sIPN). CS/PAN blend hydrogel films were prepared by solution casting technique. The blend film with optimum swelling properties was selected for the synthesis of sIPN. CS in the blend was crosslinked with the vapors of Glutaraldehyde (GTA) to prepare sIPN. The fabricated CS/PAN blend and sIPN hydrogels films were characterized with Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and field emission scanning electron microscope (FESEM). The kinetics of swelling, bound and unbound waters and aqueous stability were determined experimentally. FESEM showed good miscibility between CS and PAN, FTIR showed no chemical interaction between CS and PAN; however, it did show a doublet for the sIPN, TGA showed improved thermal stability and swelling kinetic followed second order kinetics. The degree of swelling of the sIPN hydrogels samples at room temperature varied from ~2200 % (with a fair degree of stability (~30 %)) to ~1000 % (with high degree of aqueous stability (43 %)) with increase in the crosslinking time. The calculated unbound water (WUB) max., for the blend was 52.3 % whereas for the bound (WB) the max., was 41.9 %. However, for sIPN hydrogel films, the WUB water decreased (max. 21.0 %) where as the WB increased (max. 52.0 %). The decrease in WUB and increase in the WB is attributed to the formation of a compact structure and increase in the contact area between the water and polymers in sIPN hydrogels due to the induction of new water contacting point in these hydrogel films, respectively.  相似文献   

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