Nanoporous Membranes Prepared from Homogeneous Lamellar Structure Developed via Biaxial Melt-Drawing of Ultra-High Molecular Weight Polyethylene/Normal Molecular Weight Polyethylene Blend Films

Biaxial melt-drawing of blend films composed of ultra-high molecular weight polyethylene and normal molecular weight polyethylene produced a unique network structure consisting of 30-nm thick homogeneous folded chain crystals. Subsequent biaxial solid-drawing produced a nanoporous structure covering a large area of the membrane surface (120 mm × 120 mm). Effects of preparation parameters, including annealing and subsequent solid-drawing, on resultant nanoporous morphology are also testified to achieve the desirable membrane. The higher gas permeability coefficients of the nanoporous membranes indicate that these nanopores are interconnected along the thickness direction. Despite such excellent porosity, the tensile strength reached 30 MPa, which is similar to that for the initial non-porous film. Consistence of membrane porousness and robustness is highly desirable for various separation applications, including filtration, water purification, dialysis, and lithium-ion batteries.     

聚乙二醇共混体系的研究进展

综述了近年来聚乙二醇（PEG）共混改性体系的研究进展以及应用情况,对其发展前景进行了展望。PEG与高分子材料混容性好,是应用很广的共混改性材料。PEG共混材料大多采用溶液共混法、熔融共混法和化学交联法制备。采用PEG共混改性其他材料一方面可改善脆性,提高抗冲击性能,另一方面也可提高材料的亲水性和水溶性。     

Preparation of Carbon Membranes Derived from Polymer Blends in the Presence of a Thermally Labile Polymer

Abstract

Carbon membranes for gas separation were prepared from the polymer blend consisting of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and polyvinylpyrrolidone (PVP) as the thermally stable and labile polymer, respectively. The PPO/PVP derived carbon membranes with lower PVP concentrations than 0.6 wt% showed decreased gas permeances and increased permselectivity due to decrease in the pore properties (pore volume and surface area). Meanwhile, gas permeance increased for the carbon membranes prepared with higher PVP concentrations than 0.6 wt% due to the enhanced diffusional pathways for the gas transport through carbon membranes especially in the domain of the thermally labile polymer. It is considered that the introduction of the thermally labile polymer leads to control the pore structure through the permeation results for the carbon membrane derived from the polymer blend.     

Mechanical Properties of Porous Polylactide/Chitosan Blend Membranes

Porous membranes were fabricated using chitosan and poly(DL ‐lactide) or poly(L ‐lactide) blends through a combinatorial technique. Well‐controlled porous structures could be achieved by optimizing processing conditions. The ductility and toughness of dry porous membranes were improved by incorporating an increased amount of chitosan, and the physical strength and dimensional stability of hydrated porous membranes were preserved if the components were used in a suitable ratio. Although there were measurable differences in the pore‐size distributions of membranes with the same composition prepared under identical conditions, this showed no effect in their dry states.

     

反应性聚乙二醇与环氧丙烯酸树脂共混改性及其涂膜性能的研究

用马来酸酐和聚乙二醇合成具有反应活性端基的聚乙二醇（PEG-MAH）,并用其对环氧丙烯酸酯（EA）进行物理共混改性,测定了改性环氧丙烯酸酯固化膜的性能.试验结果表明,反应性聚乙二醇参与了环氧丙烯酸树脂的固化反应,提高了环氧丙烯酸树脂的冲击强度和附着力,但耐热性、耐酸碱性和耐水性降低.讨论了不同用量的反应性聚乙二醇（PEG-MAH）对涂膜性能的影响,结果表明加入20％用量的PEG-MAH涂层具有较好的综合性能.     

Application Studies of Cellulose Acetate and Polymethylmethacrylate Blend Ultrafiltration Membranes

The preparation of novel membranes based on cellulose acetate and polymethylmethacrylate blends in the absence and presence of the pore former by solution blending and ultrafiltration set up was carried out. The effect of compaction time on pure water flux at higher transmembrane pressure for various polymer compositions of the above blends both in the presence and absence of the pore former PEG 600 at different concentrations were reported for individual polymer blends. The pure water flux at 345 kPa, Molecular weight cut-off (MWCO). The application of the characterized CA/PMMA blend membranes for the separation of proteins such as Bovine Serum albumin, Egg Albumin, Pepsin, and Trypsin, and toxic heavy metals such as Cu(II), Ni(II), and Zn(II) using polyethyleneimine as complexing agent have been attempted and the results indicate the efficiency of the ultrafiltration blend membranes.     

Novel Composite Membranes for Gas Separation: Preparation and Performance

High performance composite membranes based on molecular sieving silica (MSS) were synthesized using sols containing silicon co-polymers (methyltriethoxysilane and tetraethylorthosilicate). Alpha alumina supports were treated with hydrochloric acid prior to sol deposition. Permselectivity of CO2 over CH4 as high as 16.68 was achieved whilst permeability of CO2 up to 36.7 GPU (10–6 cm3 (STP) cm–2 · s–1 · cm Hg–1) was measured. The best membrane's permeability was finger printed during various stages of the synthesis process showing an increase in CO2/CH4 permselectivity by over 25 times from initial support condition (no membrane film) to the completion of pore structure tailoring. Transport measurement results indicate that the membrane pretreated with HCl has highest permselectivity and permeation rate. In particular, there is a definite cut-off pore size between 3.3 and 3.4 angstroms which is just below the kinetic diameters of Ar and CH4. This demonstrates that the mechanism for the separation in the prepared composite membrane is molecular sieving (activated diffusion), rather than Knudsen diffusion.     

耐溶剂高分子纳滤膜研究进展

介绍了耐溶剂高分子纳滤膜的应用现状及存在的问题,重点讨论了聚乙烯醇、壳聚糖、聚酰亚胺及聚二甲基硅氧烷纳滤膜的制备及改性方法,并指出了耐溶剂高分子纳滤膜的发展方向。     

Recent Applications of Polymer Blends in Gas Separation Membranes

Polymeric membranes are extensively used for gas separations but their performance is limited by the upper bound trade‐off discovered by Robeson in 1991. Among the attractive modifications available to increase the performance of polymeric membranes, polymer blending is a unique technique because it offers a time‐ and cost‐effective method of tuning the properties of membranes. A variety of polymer blends has been explored in recent years. The application of polymer blends in gas separation membranes is described by critically analyzing the performance of polymer blend membranes. Polymer blend membranes of different polymer pairs are reviewed and evaluated in terms of phase behavior, permeability, and selectivity.     

PEGDME强化PVDF/PP复合膜的CO2分离性能

膜分离技术具有投资小、设备简单等优点,目前广泛应用于CO2分离等方面,膜材料是膜分离技术的核心。研究表明,聚合物中醚氧基团的存在可有效提高膜对CO2的渗透速率和选择系数。聚乙二醇二甲醚(PEGDME)结构中含有丰富的醚氧基团,同时端基空间位阻提供了较高的CO2扩散系数。本文以液态PEGDME为添加剂,聚偏氟乙烯(PVDF)为共混膜材料,利用聚丙烯(PP)多孔膜为支撑,通过溶剂蒸发法制备出具有良好分离性能的PEGDME-PVDF/PP共混复合膜。结果显示,随着PEGDME含量的升高,复合膜对CO2的渗透速率和CO2/N2选择系数均呈上升趋势,当PEGDME共混含量达到50%时,CO2的渗透速率为42.9GPU,CO2/N2选择性为47.5;随着PVDF浓度的增加,CO2的渗透速率呈下降趋势,CO2/N2的选择系数则缓慢上升;适当降低溶剂蒸发温度,PVDF结晶度降低,有助于提高膜性能;当溶剂蒸发温度为30℃时,PEGDME-PVDF膜对CO2的渗透速率达到84.7GPU,CO2/N2的选择系数达到47.2。     

Separation of CO2/N2 Gas Mixture through Carbon Membranes: Monte Carlo Simulation

Abstract

Monte Carlo simulation method is employed to investigate separation behavior of gas mixture composed of carbon dioxide and nitrogen through a model carbon membrane under the different conditions. The simulation gives insight into the separation mechanism to a certain extent, which is based on the loading and diffusion of carbon dioxide and nitrogen in the carbon membrane with different pore size. The simulation results indicate that the carbon dioxide can be adsorbed on the surface of membrane wall more strongly, whereas the diffusion rate of nitrogen is more prominent. When the separation condition alters, the influence of the two main factors mentioned above on transport of gas molecules in membranes becomes different. Therefore, the equilibrium selectivity of nitrogen and carbon dioxide changes correspondingly.     

纳米碳管/聚合物复合材料的研究进展

综述了纳米碳管 /聚合物复合材料的概况及制备方法以及制备中存在的问题。     

分析测试分光光度法测定不同分子量聚乙二醇浓度

用分光光度法研究了不同分子量聚乙二醇的最大吸收波长,考察了显色剂用量、显色时间等因素对聚乙二醇溶液吸光度的影响,得到的优化测试条件为:碘用量1.0mL,BaCl2用量1.2mL,显色时间控制在1200～1400s之间。该方法操作简单、稳定性好、准确度高,便于推广应用。     

膜法分离二氧化碳研究现状及发展趋势

从膜法气体分离的优点出发,阐述了膜法分离CO2的原理、工艺流程,并将其应用于分离烟道气中的CO2.介绍了几种常见的分离CO2的膜材料,针对现有膜材料的缺点,提出了改进方法,展望了膜法分离CO2的发展方向.     

分光光度法测定不同分子量聚乙二醇浓度

用分光光度法研究了不同分子量聚乙二醇的最大吸收波长，考察了显色剂用量、显色时间等因素对聚乙二醇溶液吸光度的影响，得到的优化测试条件为：碘用量1．0mL，BaCl2用量1．2mL，显色时间控制在1200～1400s之间。该方法操作简单、稳定性好、准确度高，便于推广应用。     

Whey Protein-Pullulan (WP/Pullulan) Polymer Blend for Preservation of Viability of Lactobacillus acidophilus

In this study, whey protein isolate-pullulan (WP/pullulan) microspheres were developed to entrap the probiotic Lactobacillus acidophilus NRRL-B 4495 by spray-drying technique. Microcapsules were analyzed for physicochemical characteristics including morphology, particle size, moisture content, water activity, dissolution time, and color properties. Results revealed that microcapsules were spherical in shape and obtained particle sizes between 5 and 160 µm, with an average size of around 50 µm. Blending pullulan with WP provided enhanced survival of probiotic bacteria during spray drying with a final viable cell number of 8.81 log CFU/g of microcapsule. Encapsulated probiotics were also found to have significantly (p ≤ 0.05) higher survived cell numbers compared to free probiotics under detrimental gastrointestinal conditions. Moreover, dissolution analysis suggested that protein-polysaccharide powdered microcapsules showed pH-sensitive dissolution properties in simulated gastric juice and simulated intestinal juice.     

Ceramic Supported PDMS and PEGDA Composite Membranes for CO2 Separation

Composite membranes have attracted increasing attentions owing to their potential applications for CO2 separation. In this work, ceramic supported polydimethylsiloxane （PDMS） and poly （ethylene glycol） diacrylate （PEGDA） composite membranes were prepared. The microstructure and physicochemical properties of the compos- ite membranes were characterized. Preparation conditions were systematically optimized. The gas separation performance of the as-prepared membranes was studied by pure gas and binary gas permeation measurement of CO〉 N2 and H〉 Experiments showed that PDMS, as silicone rubber, exhibited larger permeance and lower separation factors. Conversely, PEGDA composite membrane presented smaller gas permeance but higher ideal selectivity for CO2/N2. Compared to the performance of those membranes using polymeric supports or freestanding membranes, the two kinds of ceramic supported composite membranes exhibited higher gas permeance and acceptable selectivity. Therefore, the ceramic supported composite membrane can be expected as a candidate for CO2 separation from light gases.     

智能型高分子分离膜

本文把智能型高分子分离膜分为荷电型，接枝型，互穿网络型，聚电解质配合物型和导电聚合物型等五种类型，并介绍这一新领域已取得的一些进展和应用前景。     

用于CO2捕集的新型酒石酸钠交联海藻酸钠膜的制备（英文）

The membrane-based CO2 separation process has an advantage compared to traditional CO2 separation technologies. The membrane is the key of the membrane separation process. In this paper, preparation, characteriza-tion and laboratory testing of the membrane, which was prepared from sodium alginate, hydrogen bond cross-linked with sodium tartrate and used for CO2/N2 separation, were reported. The resistance to SO2 of the membrane was also investigated. The experimental results demonstrate that the membrane possesses a high resistance to SO2. Finally, based on experimental results, the economic feasibility of the membrane used for CO2/N2 separation was evaluated, indicating the two-stage membrane process can compete with the traditional chemical absorption method.