Influence of Relative Humidity on Polyvinyl Alcohol (PVA) Nanofibers for High-Efficiency Air Filter

The influence of relative humidity( RH) on the properties of electrospun polyvinyl alcohol( PVA) nanofibers that might determine the application of nanofibers in high-efficiency air filters is not clear. PVA nanofiber mat was prepared between two hot airthrough ES( polyethyene( PE) and polypropylene( PP) composite fiber) non-woven substrates as a sandwich structure nanofiber composite filter using an electrospinning technique combining with an ultrasonic sewing process. The filtering mechanism of the composite was discussed in detail. The effects of nanofiber diameters,nanofiber layer thickness and RH in environment on the properties of PVA nanofibers were investigated by scanning electron microscopy( SEM), X-ray diffraction( XRD), automatic filter tester and universal strength tester. The results showed that the PVA nanofiber composite fabrics had high filtration efficiency with lowpressure drop and there was a negative correlation between filtration efficiency and nanofiber diameter. After keeping in a high RH environment for several hours, the mechanical property of PVA nanofiber composites was deteriorated but the high filtration efficiency was increased.     

PVA/NiO复合纳米纤维的制备及光催化性能

采用静电纺丝法,以聚乙烯醇(PVA)和硝酸镍(Ni(NO3)2)为前驱物,制得PVA/Ni(NO3)2纤维;再以尿素(CO(NH)2)为碱源,通过水热合成法制备了PVA/NiO复合纳米纤维.利用X射线衍射(XRD)、红外光谱(FT-IR)、扫描电镜(SEM)和透射电子显微镜(TEM)等分析测试手段对样品的形貌和结构进行了表征,以罗丹明B为目标降解物,考察了PVA/NiO复合纳米纤维的光催化活性.结果表明:NiO纳米粒子均匀地负载于PVA纳米纤维上,形成了具有良好光催化活性的PVA/NiO复合纳米纤维光催化材料.     

LiFePO4/CNT复合材料的制备及电化学性能

采用溶胶凝胶-微波法制备LiFePO4/碳纳米管(CNT)复合正极材料.考察不同微波时间和CNT含量对其电化学性能的影响,并通过X射线衍射(XRD)和扫描电子显微镜(SEM)对样品的晶型结构和表面形貌进行表征.结果表明:掺CNT量为2%(质量分数)和微波18 min所得样品有较好的电化学性能;0.1C充放电的首次放电比容量为142 mAh.g-1,第10次循环的比容量为136 mAh.g-1.     

Wet spinning of PVA composite fibers with a large fraction of multi-walled carbon nanotubes

PVA composites fibers with a large fraction of multi-walled carbon nanotubes modified by both covalent and non-covalent functionalization were produced by a wet-spinning process.Model XQ-1 tensile tester,thermogravimetric analysis,scanning electron microscopy,differential scanning calorimetry,and wide-angle X-ray diffraction were used to characterize the properties of PVA/MWNT composite fibers.The TGA results suggested that MWNTs content in composite fibers were ranged from 5.3 wt%to 27.6 wt%.The mechanical properties of PVA/MWNT composite fibers were obviously superior to pure PVA fiber.The Young's modulus of composite fibers enhanced with increasing the content of MWNTs,and it rised gradually from 6.7 GPa for the pure PVA fiber to 12.8 GPa for the composite fibers with 27.6 wt%MWNTs.Meanwhile,the tensile strength increased gradually from 0.39 GPa for the pure PVA fiber to 0.74 GPa for the composite fibers with 14.4 wt%MWNTs.Nevertheless,the tensile strength of the composite fibers decreased as the MWNTs content up to 27.6 wt%.SEM results indicated that the MWNTs homogeneously dispersed in the composite fibers,however some agglomerates also existed when the content of MWNTs reached27.6 wt%.DSC results proved strong interfacial interaction between MWNTs and PVA chain,which benefited composite fibers in the efficient stress-transfer.WXAD characterization showed that the orientation of PVA molecules declined from 94.1%to 90.9%with the increasing of MWNTs content.The good dispersibility of MWNTs throughout PVA matrix and efficient stress-transfer between MWNTs and PVA matrix may contributed to significant enhancement in the mechanical properties.     

聚乙烯醇纤维强化水泥基复合材料的抗盐冻性能

通过氯盐环境中的快速冻融试验研究了纤维体积率、冻融循环次数、粉煤灰、硅粉对聚乙烯醇(PVA)纤维水泥基复合材料抗盐冻性能的影响。通过扫描电镜观察内部微观结构随盐冻作用的变化规律、PVA纤维在水泥基体中分布情况和界面结合状况。试验结果表明:PVA纤维的掺入可明显改善水泥基复合材料的抗盐冻性能;PVA纤维在基体中分散性较好,且与水泥基体界面结合状况较好;而粉煤灰、硅粉的掺入未明显改善PVA纤维水泥基复合材料的抗盐冻性能。     

Study on the Mechanical Properties of Carbon Nanotube/Polyacrylonitrile Composite Fibers

The method of preparing the multi-walled carbon nanotubes (MWNTs)-polyacrylonitriIe (PAN) composite fibers is described and the effects of draw ratio on the mechanical properties of CNT/PAN fibers have also been discussed. The results show that the degrees of MWNTs dispersion in the polymer matrix have much effect on the mechanical properties.     

静电纺丝法制备YAG-ZrO2复合纳米纤维

运用静电纺丝技术结合热处理工艺成功制备了形貌光滑、尺寸均匀的YAG-ZrO₂复合纳米纤维.采用XRD、FT-IR和SEM探索了电压与浓度对复合纤维物相及形貌的影响.结果表明:电压为25 kV、PVA质量分数为11%时得到表面光滑、尺寸均一的复合纤维前躯体.前驱体纤维经过1 200 ℃煅烧5 h后,具有较高的结晶度,直径约为500 nm且比较均匀.为了使YAG-ZrO₂纤维增强的复合材料具有自检性,研究了YAG-ZrO₂纤维的发光性能,发现用290 nm紫外光激发YAG-ZrO₂:Tb³⁺复合纳米纤维,在581 nm处出现明显的发射峰,并发出绿光,这一现象属于Tb³⁺的⁴D₄→⁷F₄跃迁.应力-发光实验结果表明,YAG-ZrO₂:Tb³⁺纤维可以实现对铝基复合材料应力-应变的检测.     

聚乙烯醇纤维钢筋复合梁抗弯性能试验研究

掺入聚乙烯醇纤维(简称“PVA纤维”)的钢筋混凝土梁具有优良的抵抗变形能力和抗裂性能,在工程结构中具有良好的应用前景。为研究PVA纤维的掺入对PVA纤维钢筋复合梁(简称“PRC梁”)抗弯性能的影响,进行了4根PVA纤维体积掺量不同的PRC梁的静态三点弯曲加载试验。结果表明：PVA纤维的掺入并没有改变PRC梁的破坏形态,且破坏过程相似;但是掺入PVA纤维极大增强了PRC梁的抗裂性,延缓了裂缝的出现。相比于普通RC梁,0.75%(体积分数)掺量下的PRC梁开裂荷载提高了2.1倍;同时,掺入PVA纤维能够小幅增加PRC梁的抗弯承载力,在加载过程中,PVA纤维混凝土与钢筋能够更好地协同工作,从而增强了PRC梁的持荷变形能力;荷载位移曲线的积分面积表明(利用Origin曲线积分发现)PRC梁在加载过程中吸收的能量更多,因此,掺入PVA纤维能够有效增强PRC梁的延性。     

Magnetic Cotton Fabric Coated with Poly( vinyl alcohol )( PVA )/Magnetic Attapulgite( MAT ) Composite Solution

Magnetic fiber or fabric incorporating magnetic particles was widely used in the field of magnetic health-care.The cotton fabric was modified with poly(vinyl alcohol)(PVA)/magnetic attapulgite(MAT)composite solution by coating,which was the PVA solution blended with MAT.The mechanical and magnetic properties were characterized by scanning electronic microscopy(SEM),vibrating sample magnetometer(VSM)and tensile strength test.The results of SEM show that MAT can scatter uniformly in the PVA film and the PVA/MAT polymer film has good combination with cotton fabric.The results of other tests show that the addition of PVA/MAT polymer film not only brings uniform magnetism to cotton fabric,but also increases the mechanical strength of the material.Besides,the proportion of PVA/MAT and dipping time are studied in order to determine the best parameters for further study on magnetic cotton fabric.     

大豆蛋白复合纤维热学性能研究

对比聚乙烯醇（PVA）膜,采取热重分析和差示扫描量热法研究了大豆蛋白/聚乙烯醇复合纤维（以下简称sp/PVA）的热学性能,并分析了聚乙烯醇及sp/PVA热性能的差异.不同sp/PVA测试结果表明大豆蛋白含量及线密度影响纤维的热性能.热重分析中,大豆蛋白含量多少影响失重过程长短,纤维线密度越低,热性能越好.差示扫描量热结果显示,sp/PVA的第一个峰为玻璃化转化区,第二个峰主要是由于聚乙烯醇的熔融引起.     

ZnO/Zn/CNT三维多孔复合结构的制备及对甲基橙的无光催化降解

以碳纳米管(CNTs)、纳米ZnO/Zn复合粉体和造孔剂聚甲基丙烯酸甲酯(PMMA)微球为原料,通过超声分散、真空抽滤、焙烧的方法制备ZnO/Zn/CNT三维多孔复合结构.利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、能谱仪(EDS)和拉曼光谱仪对样品的微观结构及成分进行表征.结果显示,样品内部存在大量的连通孔,ZnO/Zn复合粉体均匀分散于CNTs所构筑多孔结构的孔隙中.在多孔复合结构的制备过程中,ZnO晶体结构未发生变化也无杂质生成.多孔复合结构对模拟污染物甲基橙的暗室催化降解结果证明,由于独特的孔结构存在和ZnO与CNTs的协同作用,使得样品在80min时对甲基橙的降解率达99.9%.     

基于分散技术的聚乙烯醇纤维沥青胶浆疲劳性能分析

为探究聚乙烯醇纤维（Polyvinyl alcohol fiber）分散后沥青胶浆的疲劳变化规律,探索性地采用旋转活塞式拌和法对PVA纤维沥青进行拌和分散,从PVA纤维的微观形貌出发,探究其纤维提高疲劳性能的原因。另外利用动态剪切仪（DSR）PVA纤维沥青进行时间疲劳扫描,通过复数模量衰减Nf50和累积耗散能比Nder对PVA纤维沥青胶浆疲劳性能进行评价。试验结果表明,PVA纤维表面有随机分布的凸起颗粒以及非完整光滑的表面,这种结构与沥青形成了很好的适配性,PVA纤维在沥青中起到了稳定、增粘、复合加筋作用,从而综合提高了沥青疲劳性能。同时,Nf50和Nder都能很好地评价沥青的疲劳性能,从物理表达清晰、易于确定、结构设计安全角度出发,更推荐采用累积耗散能比Nder指标用于评价沥青疲劳性能。     

PVA／MMT纳米复合材料的制备及性能表征

采用溶液插层-流延成膜法,以聚乙烯醇和钠质蒙脱土为原料,制备出不同蒙脱土含量的PVA／MMT纳米复合材料薄膜,采用XRD,FTIR,SEM对纳米复合材料的结构进行了表征,并用TGA测试了纳米复合材料的热性能,同时,测试了纳米复合材料的力学性能和耐水性能。XRD测试结果表明,复合材料中的蒙脱土的片层间距显著增大,表明PVA分子进入了蒙脱土片层之间。FT—IR分析可以看出,蒙脱土的加入使PVA中C—O的伸缩振动峰变弱。SEM观察到纳米复合材料断裂时裂纹的微观结构。TGA测试表明,纳米复合材料的热分解温度比纯PVA有较大提高。该纳米复合材料具有良好的力学性能和耐水性,可作为一种新型的包装材料。     

Dynamics Model and Simulation of Polyethylene Terephthalate （PET） Hollow Fiber

On the basis of melt-spinning, the dynamics model of polyethylene terephthalate (PET) hollow fiber is established.The effects of spinning conditions on hollow ratio are discussed and verified. Because of the different quenching conditions, there exist differences of the hollow ratio and the vitrification distances between different cycles. The important role of the quenching conditions on the melt-spinning of PET hollow fiber is also mentioned.     

多金属氧酸盐对聚乙烯醇在水中溶胀性能的影响

制备了含不同结构多金属氧酸盐(HPA)和含量不同多金属氧酸盐的聚乙烯醇(PVA)纤维材料,并用IR、XRD光谱和扫描电镜(SEM)对其进行了表征.针对PVA在水中的溶胀性能,系统地研究了多金属氧酸盐的种类、含量、交联温度和时间对PVA纤维材料的水溶性的影响.     

纳米羟基磷灰石/聚乙烯醇/海藻酸钠复合水凝胶的结构与性质研究

采用溶液共混法制备了纳米羟基磷灰石/聚乙烯醇/海藻酸钠三元复合水凝胶材料,测定了复合材料的含水率,采用燃烧实验、扫描电子显微镜、傅里叶红外光谱及X射线衍射对复合材料的结构进行了表征和分析,并研究了复合材料的吸水性.结果表明,制备的复合水凝胶材料组成均匀,各组分间存在相互作用,并且具有好的吸水和保水性能,该复合水凝胶材料可作为一种人工软骨生物材料.     

聚苯乙炔/碳纳米管复合材料的制备及导电性

以无水A lC l3为催化剂合成了聚苯乙炔(PPA)、用浓H2SO4进行磺化改性,并通过共混制得了PPA/碳纳米管(CNT)及磺化PPA/CNT复合材料;研究了复合材料的导电性及电导率与CNT含量的关系。结果表明:磺化PPA/CNT导电阈值比PPA/CNT的降低了1%,前者达到极限电导率所需CNT的量是后者的10%;X-射线衍射(XRD)测试表明,在CNT界面上的磺化PPA有新的晶型产生。     

Preparation of alumina supported on carbon nanotubes and its application in fluoride adsorption from an aqueous solution

A novel material, alumina supported on carbon nanotubes (Al₂O₃/CNT), was prepared from carbon nanotubes and Al(NO₃)₃.X-ray diffraction (XRD) spectra demonstrate that alumina is amorphous, and scanning electron microscope (SEM) images show that CNT and alumina are homogeneously mixed. Furthermore, the fluoride adsorption behavior on the surface of Al₂O₃ /CNT has been investigated and compared with other adsorbents. The results indicate that Al₂O₃/CNT has a high adsorption capacity, with a saturation adsorption capacity of 39.4 mg/g. It is also found that the adsorption capacity of Al₂O₃/CNT is 3.0—4.5 times that of g-Al₂O₃ while almost equal to that of IRA-410 polymeric resin at 25℃. The adsorption isotherms of fluoride on Al₂O₃/CNT fit the Freundlich equation well, and optimal pH ranging from 5.0 to 9.0.     

花岗岩石粉-高韧性水泥基复合材料的制备与性能

研究了掺花岗岩石粉的高韧性水泥基复合材料的基本力学性能。采用废弃花岗岩石粉部分取代磨细砂,制备具有不同石粉质量取代率的水泥砂浆;并对其进行抗压、抗折试验分析,得到最优的石粉取代率约为25%;在此最优石粉取代率的基础上配制出掺花岗岩石粉的高韧性水泥基复合材料;并研究聚乙烯醇(PVA)纤维体积掺量(0~1.5%)及其长径比(158~316)对混凝土复合材料基本力学性能的影响。研究结果表明,试验中,当花岗岩石粉掺量一定时(25%),纤维体积掺量1.5%且长径比237时电镜扫描显示纤维与基体界面结合最紧密,力学性能最佳,此时的极限拉应变高达3.03%,约为普通水泥基材料的300倍。     

PVA覆膜对Kevlar纤维表面化学镀Cu层性能的影响

通过聚乙烯醇 (PVA) 覆膜处理的方法提高了Kevlar纤维表面金属镀层稳定性和完整性,从而提升了镀层的抗剥落能力.采用弯折剥离实验考察了镀层的抗剥落破坏情况、采用电阻仪和电子万能试验机测试了试样的导电性和力学性能,利用扫描电子显微镜(SEM)和X射线光电子能谱(XPS)研究了试样的表面形貌和表面化学价态. 结果表明:PVA覆膜能够有效提升金属镀层的抗剥落破坏能力;随着PVA水解浓度的增加,PVA覆膜Cu/Kevlar纤维的表面电阻增加而柔韧性降低;当PVA溶液的水解质量浓度为5 g/L时,PVA覆膜Cu/Kevlar纤维的柔韧性、导电性和抗剥落能力能够维持在最佳状态;在此浓度下,PVA覆膜Cu/Kevlar纤维的表面电阻为0.41 Ω/cm,单丝拉伸强度为2.396 GPa,Weibull分布拟合度为0.988 1.