PEG含量对PVDF/PEG共混膜性能的影响

以聚乙二醇(PEG)为添加剂,利用非溶剂致相分离法制备了聚偏氟乙烯(PVDF)/PEG共混膜,使用傅里叶变换红外光谱、X射线衍射、扫描电子显微镜、接触角测量等表征测试方法,研究了PEG含量对PVDF/PEG共混膜性能的影响。结果发现,PEG的加入使PVDF的结晶性能下降,同时也使其结构发生了变化。但是由于PEG的亲水性,当PEG的质量分数小于5%时,PVDF/PEG共混膜的亲水性随着PEG含量的增大而逐渐得到改善。     

PEG/GO/TiO2纳米复合材料改性PVDF膜的制备及其抗污性能

为改善聚偏氟乙烯(PVDF)膜的抗污性能,以聚乙二醇2000接枝的GO/TiO₂(PEG/GO/TiO₂)纳米复合材料为添加剂,通过非溶剂诱导沉淀相分离法制备了一系列PEG/GO/TiO₂/PVDF复合超滤膜。采用FTIR、SEM和接触角测试仪对其结构和形貌进行了表征,采用超滤法评价其纯水通量和抗污性能。结果表明,当PEG/GO/TiO₂纳米复合材料质量分数为0.60%时,制备的PEG/GO/TiO₂/PVDF复合超滤膜(记为0.60%PEG/GO/TiO₂/PVDF)表现出最佳的亲水性和抗污性能,其接触角比PVDF膜下降8.2°,总孔隙率增加13.40%,PEG/GO/TiO₂纳米复合材料在PVDF膜中分散较均匀。在0.08 MPa的工作压力下,0.60%PEG/GO/TiO₂/PVDF的纯水通量高达282.44 L/(m²·h),对腐植酸溶液的过滤通量为131.96 L/(m^2...     

纳米TiO2复配添加剂对PVDF中空纤维膜结构和性能的影响

该文将纳米二氧化钛（TiO2）粒子与高分子致孔剂、非溶剂、表面活性剂和无机盐4类制膜添加剂复配处理,采用浸没沉淀相转化法制备聚偏氟乙烯（PVDF）-TiO2复合中空纤维膜。通过扫描电子显微镜、X射线衍射、能谱、拉伸试验、接触角测定和截留试验分别对复合膜的微观孔结构、晶相结构、Ti元素分布、机械性能、亲水性、过滤性能和抗污染性能进行了表征,讨论了纳米TiO2粒子对PVDF膜结构和性能的影响。结果表明通过改变复配添加剂中TiO2粒子的含量,可以有效调控复合膜的结构和性能。当复配添加剂中w（TiO2）为2％（占PVDF固含量的质量分数埘％）时,纯水通量由216L／m^2·h提高至402L／m^2·h,牛血清蛋白截留率由95％降低至90％,复合膜整体性能较为优异。     

大孔径PVDF平板微孔膜的制备与性能研究

对大孔径聚偏氟乙烯(PVDF)均质膜的制备及其结构性能进行了研究.结果发现,聚合物浓度、凝固浴组成、添加剂种类是影响膜结构与性能的主要因素.通过对这三个制膜条件的控制及优化,制备出多孔的上下表面、全海绵状孔结构的断面、性能良好、结构可控的PVDF微孔膜.上下表面孔径范围为0.2～3μm,水通量在200～600L/m2·h(0.1MPa)的范围.尤其是纳米TiO2粒子添加剂的加入,使得膜的强度大大提高.     

混合溶剂对TiO2/PVDF平板超滤膜性能和结构的影响

采用N,N-二甲基乙酰胺(DMAC)和N-甲基吡咯烷酮(NMP)为混合溶剂制备PVDF超滤膜。考察了不同混合比例的DMAC和NMP对膜性能及膜结构的影响,同时利用扫描电子显微镜(SEM)对膜表面及断面结构进行分析,原子力学显微镜(AFM)对膜表面粗糙度进行了分析,利用接触角测量仪对膜表面接触角进行了测量。结果表明,使用混合溶剂对膜孔径和膜亚层结构影响较大,但混合溶剂对膜孔隙率和接触角基本没有影响。当混合溶剂DMAC/NMP为1:2时,膜性能达到最优,孔隙率为70%,平均孔径为0.24μm,水通量为373 L.m-2.h-1,截留率为88%。     

用于处理染料废水的PVDF/TPU共混中空纤维膜的制备

采用相转化法制备PVDF／TPU共混中空纤维膜，以PVP为添加剂可以改善成膜性能。通过水通量超滤实验、牛血清白蛋白截留实验、扫描电子显微镜表征膜的表面与截面结构分析得出铸膜液中纤维膜的质量分数为16％，m（PVDF）：m（11Pu）为80：20，添加5％PVP时制备的膜的综合性能最佳。对不同的溶液包括BSA、PVPK30、PEG10000、染料活性艳蓝KN-R进行截留实验分析膜过滤性能。在pH范围为1—14时，膜的水通量及截留率均无明显变化，说明PVDF／TPU共混中空纤维膜具有良好的抗酸、碱性。用清水冲洗10min后，膜污染的恢复率即可达到86．5％，膜的抗污染性能良好。     

TiO2纳米粒子对PVDF超滤膜的结构与性能影响研究

采用溶胶-凝胶法制备了不同纳米TiO2溶胶含量的TiO2/PVDF超滤膜,探讨TiO2溶胶及其含量对膜性能及结构的影响,并利用X射线衍射、扫描电子显微镜、红外光谱和接触角测量仪表征了复合膜的结构.结果表明,经纳米TiO2溶胶改性后,TiO2/PVDF复合膜的孔隙率、接触角和结构等都发生了显著的变化,在TiO2溶胶添加质量分数为4％时条件下,膜的孔隙率为74.5％,水通量为430.6L·m-2·h-1,截留率为82.5％.     

聚偏氟乙烯-溶剂-非溶剂-添加剂体系膜制备及其性能

以聚偏氟乙烯(PVDF)为膜材料,测定了不同温度下PVDF/DMAc、PVDF/DMF和PVDF/NMP溶液的混合参数,得出非溶剂沉淀能力大小为:甘油>DEG>PEG200>PEG400,并与Hansen溶解度的理论计算值进行了比较。此外,讨论了不同PEG400在混合溶剂中的比例以及不同添加剂对膜性能的影响;PEG400的加入,使膜的纯水通量、机械性能均有所提高,截留率保持不变;VAH、Tween80、PEG20000和成核剂使膜的纯水通量提高到100 L/(m2.h)以上,LiCl的加入对通量影响不大。     

PA/ZIF-8/PVDF复合纳滤膜的制备及其性能

采用反向扩散法在聚偏氟乙烯(PVDF)基膜表面原位生长一层均匀、致密的金属有机骨架材料ZIF-8纳米晶体层,并进一步优化界面聚合反应,制备高性能聚酰胺(PA)/ZIF-8/PVDF复合纳滤膜.采用SEM、XRD、FTIR、AFM、XPS、水接触角测定仪以及固体表面Zeta电位仪对ZIF-8/PVDF复合膜及PA/ZIF-8/PVDF复合纳滤膜的组成、结构和形貌进行了表征,考察了ZIF-8亚层的生长对界面聚合反应、复合纳滤膜结构及性能的影响.结果表明,ZIF-8晶体亚层在PVDF膜表面的均匀连续生长改善了PA分离层与PVDF基膜的界面相容性,提高复合纳滤膜PA分离层的交联度.在0.6 MPa下,复合纳滤膜纯水通量可达24.05 L/(m2·h),对MgSO4、Na2SO4、NaCl和MgCl24种盐的截留率分别达到97.34％、93.57％、89.31％和85.16％,具有优异的抗污染性能.     

没食子酸诱导构筑MXene层状孔道的PVDF抗污膜

膜污染是目前影响膜技术发展的制约因素之一.为提高聚偏氟乙烯(PVDF)超滤膜的亲水性和抗污染性,以PVDF为膜材料,聚乙二醇(PEG 6000)为添加剂,采用相转化法制备PVDF平板膜;以没食子酸(GA)和聚乙烯亚胺(PEI)的交联网状结构为功能化平台,利用真空辅助抽滤法将Ti3C2Tx MXene沉积到膜上,进而达到对PVDF膜改性的目的.接触角测试结果表明,GA涂层与Ti3C2Tx MXene沉积层的加入使PVDF膜的水接触角从92.减小为30°,膜的亲水性明显提高;膜与牛血清蛋白(BSA)间的黏附力从267.5 pN降低至23.5 pN,通量恢复率高达98.78％,表明改性后,膜的抗污染能力明显增强.     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.     

环氧树脂羟基值测定方法的研究

利用乙酸酐、吡啶和浓硫酸混合的乙酰化试剂测定环氧树脂中羟基值含量的方法具有操作简便、滴定终点明显和分析结果误差小等优点。     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

几种针状焦性能对比

针状焦分石油系和煤系两大类,这主要取决于针状焦的原料来源。在同一系列中由于原料不同和工艺条件不同 ,针状焦的各自性能也不相同。针状焦是生产超高功率石墨电极和高功率石墨电极的主要原料 ,针状焦的性能对石墨电极的质量有至关重要的影响。所以对针状焦性能以及其对石墨电极质量影响的研究十分必要的。以下是常用的几种进口针状焦和国产针状焦的性能对比。１原料性能分析对比原料试样包括４种针状焦 ,其中两种为进口针状焦：三菱针状焦和新日化针状焦;另两种为国产针状焦：鞍山针状焦和锦州针状焦。其中除锦州针状焦是石油系针状焦外…     

用两个形状指数表征粉煤灰颗粒形貌的研究

引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。