Liquid permeation of organic mixture by surface-modified polyethylene membrane

Linear low-density polyethylene membranes were prepared by a casting method. IN order to modify the surface, the membrane was irradiated with UV light. In an atmosphere of carbon disulfide vapor, multiple internal reflection spectra observations showed that the surface of membrane had a carbonyl group. The casted membrane is an asymmetric membrane. When the flat surfce of membrane faces the upstream side, the flux of the membrane is twice as that of the other surface of membrane. From the comparision of the pervaporation characteristics of casted membrane and blown film, the crystallinity of membrane affects the separation factor and flux of the membrane. The higher the crystallinity of the membrane, the better the selectivity, and the poorer the flux.     

Chemiluminescence of polyethylene induced by UV irradiation

Summary The chemiluminescence (CL) of polyethylene (PE) film induced by UV irradiation was investigated. CL parameter, I₀, which indicates the oxidation rate under UV irradiation was obtained from a kinetic analysis. The I₀ was found to be valuable to evaluate the durability of PE films.     

聚二甲基硅氧烷膜中乙醇-水的吸附和渗透蒸发行为

以乙醇/水体系为研究对象,结合F lory-Huggins理论,讨论溶胀过程的热力学行为,用以分析和考察聚二甲基硅氧烷(PDMS)膜在乙醇/水中的溶胀特性及组分间的耦合效应。结果表明,在乙醇质量分数20%—40%,膜的溶胀程度最大。渗透蒸发实验表明,水的渗透速率在乙醇质量分数不大于30%范围内变化很小,而乙醇的渗透速率基本随溶液中乙醇质量分数增加而增大。     

Preparation of low-density polyethylene composites by UV irradiation

Summary Composites of low-density polyethylene were prepared by the sorption of vinylic monomers and a photoinitiator into a polymer matrix, followed by UV irradiation. Gravimetric determinations showed that 2–4% incorporation of the polymer in the host matrix is possible by this method. Transmission and reflectance infrared spectra measurements showed that the vinylic polymer is lodged in the bulk of the polymer film with no surfacial deposition.     

Hydraulic permeation of liquids through swollen polymeric networks. II. Liquid mixtures

The hydraulic permeation of toluene–cyclohexanone and isooctane–CCl₄ mixtures through a membrane, a rubber network, was studied. No separation of components occurred in this mode. The mixture flux data were successfully analyzed using a solution–diffusion theory by treating the mixture as if it were a single component with properties of the mixture. Diffusion coefficients determined in this way appear to be governed by frictional forces having a hydrodynamic origin. Slight separation of the components did occur when the pervaporation mode of operation was used. The significance of this is discussed.     

PET溶胀聚合反应研究进展

溶胀聚合是制备高分子质量聚酯的有效手段.文章综述了溶胀剂、溶胀温度、催化剂浓度、氮气流量、颗粒大小及结晶对溶胀聚合反应的影响,介绍了从低粘度聚酯预聚体通过溶胀聚合制备高分子质量聚酯的工艺新思路.溶胀聚合动力学机理研究表明,溶胀促进了端基扩散,促进了溶胀反应,但溶胀对内扩散的影响尚有待进一步研究.     

Hydraulic permeation of liquids through swollen polymeric networks. III. A generalized correlation

An approximate equation was developed that permits calculation of the solvent tracer diffusion coefficient in a homogeneous swollen membrane from the measured hydraulic permeability coefficient. This relation was applied to data for 28 polymer–solvent systems that included 15 different organic solvents and 5 hydrocarbon polymer networks whose equilibrium swellings ranged from 16.1 to 91.5% polymer on a volume basis. The calculated tracer diffusion coefficient divided by the pure solvent self-diffusion coefficient for these systems formed a unique correlation when plotted versus the polymer volume fraction in the membrane. This relation agreed well with tracer diffusion coefficient data in the literature for the benzene–natural rubber system measured by radioactive tagging. Discussion centers on the evidence for the validity of the equation developed and the role of hydrodynamics on diffusion in swollen membranes.     

A structural study of polyelectrolyte gels in a unidirectionally swollen state

We investigated the structures of polyelectrolyte gels, poly(N-isopropylacrylamide-co-2-acrylamido-2-methylpropane sulfonic acid) (NIPA/AMPS) hydrogels in a unidirectionally swollen state by using small-angle X-ray scattering (SAXS). The SAXS results show that the structure of the NIPA/AMPS gels strongly depends upon the composition of NIPA/AMPS. Increase in composition of AMPS causes suppression of concentration fluctuations in the long wavelength. As a consequence, a NIPA/AMPS hydrogel with a low composition of AMPS macroscopically phase-separated at high temperatures, while microphase separation occurred for a NIPA/AMPS gel with a higher composition of AMPS. The instability in the microphase separation initially occurred in the direction perpendicular to the swelling for the latter gel. In the disordered state near the microphase separation region, an elliptic scattering pattern was observed, and the scattering intensity around the peak position in the direction perpendicular to the unidirectionally swelling was larger than that in the direction parallel to it. The behavior became more remarkable, as the interaction parameter χ became larger. These behaviors are consistent with the prediction from the Rabin-Panukov theory. The scattering vector at the scattering maximum in the perpendicular direction q_m,⊥ significantly shifted to smaller q, where q represents the magnitude of the scattering vector, when the microphase separation occurred. It is shown that the periodicity of the microphase-separated structure ranged from 300 to 400 Å.     

Structural characteristics and state of water in an acetate cellulose membrane

Experimental data have been obtained and an analysis has been performed of the degree of crystallinity and amorphism and the state of water for cellulose acetate membranes using the methods of X-ray diffraction (XRD), infrared spectroscopy and thermogravimetry. The degree of crystallinity, as well as the crystallite size, have been determined in the membrane samples before and after water absorption. It has been found that OH groups of cellulose acetate form a nonequilibrium network of hydrogen bonds between molecules and fragments in the amorphous phase of an air-dry semipermeable membrane. It has been shown that water that acts as a plasticizer causes the ordering of the macromolecular amorphous phase, which leads to a transition into the liquid crystal phase with the formation of additional capillary spaces.     

Thermoelastic and thermomechanical studies on natural rubber vulcanized in the swollen state

Three samples of natural rubber were crosslinked in n-decane solution. After the solvent had been removed, a thermodynamic investigation was made of the elastic behaviour of the samples in simple extension. Thermoelastic measurements at constant pressure and length were carried out on the first two samples. The third sample was subjected to a thermomechanical heat of extension study using a Calvet microcalorimeter. The experiments enabled the temperature coefficient of the mean-square unperturbed dimensions, 〈r²₀〉, to be derived. From the thermoelastic measurements average values for dln $\text{〈r}{}^2{}_0\text{d}\text{T}$ of (0.44 ± 0.08) × 10^?3deg^?1 and (0.38 ± 0.07) × 10^?3deg^?1 were obtained, whilst the thermomechanical measurements gave a value of (0.54 ± 0.04) × 10^?3deg^?1.     

The state of water in swollen ionomers containing sulfonic acid salts

The proton magnetic resonance relaxation times and heat capacity of water in perfluoroethylene sulfonic acid (Nafion), chlorosulfonated polyethylene (SPE), and sulfonated polysulfone (SPS) were measured as a function of temperature. Only the relaxation data for water present in Nafion conformed to the BPP model. The data indicate that the presence of fine pores, ～12 Å in diameter, causes water–surface interactions to play a significant role. For materials with the same pore size, a difference in spin-lattice relaxation time T₁ may be correlated to the Flory–Huggins parameter χ calculated for the interaction of water with the neutral portion of the polymer backbone. Only a part of the water present in Nafion and SPE undergoes freezing, while no transition was observed for water in SPS for temperatures down to ?60°C. For Nafion and SPE, the heat of fusion ΔH_f calculated from combined FID data and the DSC study was ?20 cal/g.     

Fractionation of linear polyethylene with gel permeation chromatography. IV

Reproducibility was examined on the GPC fractionation of linear polyethylenes. The experiences over the period of two and a half years were used. Calibration was done with the same batches of narrow distribution polystyrene standards. A control sample of broad-distribution polyethylene was run at each calibration. The reproducibility over ten calibrations with this control was in terms of standard deviation of ca. ±10% for the number-average and ca. ±15% for the weight-average chain length. The fractionation data of 36 commercial resins were corrected by using the control samples as an additional standard. The correction was very effective in decreasing the scattering of the data in the intrinsic viscosity–molecular weight plot, especially when the viscosity average was used for the molecular weight expression.     

Charged ultrafiltration membrane for permeation of proteins

Polyacrylonitrile-g-poly(N,N-dimethylaminoethyl methacrylate) was synthesized photochemically and quaternized. The positively charged membranes made from the quaternized graftcopolymer showed high ultrafiltration rate for water by adding poly(vinyl alcohol) to casting solution and washing it out after the casting. In buffered saline solution, the permeability of the membranes was very small at pH below isoelectric point of albumin but increased markedly at higher pH. On the other hand, the permeability for γ-globulin was very small and did not show any pH dependence.     

Preparation of anti-oil stained membrane by grafting polyethylene glycol macromer onto polysulfone membrane

In this study, anti-oil stained ultrafiltration membrane was prepared by grafting a polyethylene glycol diacrylate macromer onto a plasma-activated polysulfone membrane. The macromer formed a hydrate layer which prevented oil in emulsion from directly contacting the membrane surface, thus preventing the oil from staining the membrane. © 1994 John Wiley & Sons, Inc.     

Liquid membrane permeation of aromatic hydrocarbons in LPG condensate

Experimental data on batch permeation of aromatic hydrocarbons from liquefied petroleum gas (LPG) condensate and model benzene/3,3-dimethyl pentane and benzene/2,2-dimethylhexane mixtures in emulsion liquid membranes have been presented. Use of lipophilic surfactant in the solvent phase was found to enhance both yield and selectivity, the effect being more pronounced in the case of surfactant with moderate HLB value. Solvent with high boiling point and density was also found to be suitable, but the aromatic yield and selectivity were relatively low. Yield of, and separation factor for, total aromatics in LPG condensate were found to be lower than those observed for model hydrocarbon mixtures. However, the yield and separation factors for benzene alone are the highest and comparable to those for the model mixture. Up to 75% of benzene present in feed LPG condensate could be separated via liquid membrane permeation under suitable conditions.     

Oxygen permeation properties of BSCF5582 tubular membrane fabricated by the slip casting method

BSCF5582 tubular oxygen separation membranes were prepared using the most cost effective slip casting techniques. The optimum slurry composition was identified and a dense, and crack free 60 mm long BSCF5582 tubular membrane being successfully prepared after the programmed sintering process. The effects of the feed flow rate and the sweeping flow rate on the oxygen permeation flux of the tubular BSCF5582 membrane were investigated. The oxygen permeation flux increased with an increase of the oxygen chemical potential gradient to a maximum of 42.5 cm³/min in an O₂/N₂ condition at 1223 K for the 1.5 mm thick, 60 mm long BSCF tube, a value which corresponds to 1.42 cm³/min cm². The ionic conductivity of the oxygen was successfully calculated in the dominant electron conducting regime. The ionic conductivity was found to increase with an increase of the temperature to 900 °C, indicating that it is a thermally activated process with an activation energy of 0.70 ± 0.1 eV in an air environment.     

Physical state of radiation-polymerized polyethylene blends

The physical state of the blends of radiation-polymerized polyethylene with high-density polyethylene was studied. Only one peak was observed in DSC heating curves of the blends quenched from the melt regardless of the each polymer content. In addition, transparency of the high-density polyethylene was improved by melt blending with radiation-polymerized polyethylene. This is a characteristic of high-density polyethylene and radiation-polymerized polyethylene blends different from high-density and low-density polyethylene blends. A new peak and/or a new shoulder, however, appeared in DSC heating curves of the blends with heat treatment at 110°, 120°, and 125°C. These results suggest that the physical state of the blends quenched from the melt is one where the crystallization of the radiation-polymerized polyethylene is high hindered by the presence of high-density polyethylene. The radiation-polymerized polyethylene may remain mainly in a physical state similar to the melt. The haze value of the blends increased with heat treatment. The increase in the haze is caused by change in physical states, such as growth of spherulites and formation of microcrystals and microvoids, by the heat treatment.