摘要:

AbstractWater–ethanol permselectivity was investigated by pervaporation through composite membranes which were prepared by coating photocrosslinkable poly(vinyl alcohol) containing pendant styrylpyridinium group (0.86–3.93 mol %) on porous films. These membranes were water‐permselective, and the selectivity was dependent on the state of membranes; namely, incorporation ratio of styrylpyridinium group on poly(vinyl alcohol), molecular weight of the base polymer, coating thickness of a photopolymer, etc. Photocrosslinkable styrylpyridinium group showed, of course, the ionic character by a pyridinium moiety to work on permseparation of water effectively as well as preventing the dissolution of membranes by crosslinking. Membranes based on the higher molecular weight poly(vinyl alcohol) (P= 1700) gave the higher permselectivity of water in general than those of lower molecular weight (P= 500) one. Swelling of the polymers reached 160%, and permeation rate through the membranes increased with the increase of swelling. Selective diffusion of water was found to take place in swelling, and to play a part in the water‐permseparation through the me

ISSN:0021-8995    

DOI:10.1002/app.1988.070360801

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractSemicrystalline LaRC‐TPI is known to be capable of recrystallizing to higher melting crystalline forms upon initial melting. The behavior of these different crystalline forms has not been studied before. The present study uses techniques of differential scanning calorimetry and X‐ray diffractometry to investigate thes crystalline structural changes during recrystallization of this material. Semicrystalline LaRC‐TPIs synthesized from three different laboratories are included in this

ISSN:0021-8995    

DOI:10.1002/app.1988.070360802

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractAmidoxime polymers crosslinked with tetraethylene glycol dimethacrylate (40 wt%) and with differing water contents were prepared by poly(acrylonitrile) treatment in various quantities of toluene with hydroxylamine. Adsorption rates of uranium on the amidoxime polymers from seawater were examined in relation to their porosity. The amidoxime polymer prepared from poly(acrylonitrile) in an increasing quantity of toluene exhibits a significantly increasing water content. On the basis of mercury intrusion measurements, the increasing water content was revealed to be predominantly owing to the enhancement of porosity. The adsorption rate of uranium from seawater increased steadily with an increase of porosity, suggesting the dependence of the adsorption rate on a diffusion process of uranium into the pore domain.

ISSN:0021-8995    

DOI:10.1002/app.1988.070360803

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractControlled reactions on the inner side, outer side, and both sides of the surfaces of polysulfone ultrafiltration hollow fibers with propane sultone and Friedel‐Crafts catalysts were developed. EPMA measurements and MTR spectra for the chemically modified fibers suggested existence of CH2CH2CH2SO3−segments on the modified surfaces. The modified fibers were found to have smaller molecular weight cut‐off than nonmodified fibers, and the fibers modified on the internal surfaces gave better rejection of polyethylene glycol 6000 than those modified on the external surfaces, although the fibers that reacted with solution of the propane sultone and SnCl4at 70°C and 80°C showed negative rejection of the polyethylene gylcol. Absorption of polyethylene glycol on the modified fibers is estimated to be less than the nonmodified fibers from the flux ratios of aqueous polyethylene glycol solution to pure water. This effect is attributed to the heparinlike active group of modified

ISSN:0021-8995    

DOI:10.1002/app.1988.070360804

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractMixtures of novolac resin with pressed cottonseed in different proportions after their curing as small cylinders, and also pressed cottonseed as powder were pyrolyzed until 1000°C. Some samples follow, as well as an activation process by steam between 700 and 950°C. The weight losses of the samples are much higher, up to 500°C, while small weight losses are observed over 800°C. The weight losses for the 100% pressed cottonseed during the carbonization are essentially higher than those of the specimens also containing novolac; indeed, for the total weight losses up to 1000°C an increasing linear dependence was found with increasing proportion of the cottonseed in its mixture with novolac. The shrinkage of the specimens also containing novolac follows in general a curve similar to that of the weight losses for the corresponding case. The specific surface areas of the carbonaceous materials produced show higher values with measuring by CO2than by N2due to the larger dimensions of the N2molecule as compared to the CO2molecule, so that N2areas are more sensitive to slight changes in aperture sizes of the porous materials produced. The specific surface areas of the materials that have also been activated indicate higher values in comparison with those without activation and also higher than activated carbon commercially available. The more increased and fine porous structure of the activated carbons as compared to those only pyrolyzed become also obvious from the corresponding photos obtained by the scanning electron microscope. These results are also in agreement with the discoloring ability of the produced adsorptive media for the methylene blue from aqueous solution, following the Freundlich equation for the adsorp

ISSN:0021-8995    

DOI:10.1002/app.1988.070360805

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractGel permeation chromatography results obtained from the adsorption of alkyd from different solutions on anatase TiO2surfaces are reported, and the influences of the solvent–resin interactions in the adsorption process are discussed, covering the thickness of the adsorbed layer, the type of molecular weight species adsorbed, and its dependence on the concentration of the solution. Resin–pigment interaction was found to be influenced by the type of solvents u

ISSN:0021-8995    

DOI:10.1002/app.1988.070360806

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe glass transition temperatures (Tg) of blends of polyacrylic acid (PAA)–Nylon 6 in various proportions used as membrane material in pervaporation separation of acetic acid–water and ethanol–water mixtures were determined using differential scanning calorimetry (DSC). All the samples examined showed a singleTgwhich lay between theTgof Nylon 6 and PAA, indicating that complete miscibility was achieved in these polymer blends. Further evidence of complete miscibility was obtained by scanning electron microscopy (SEM) of cross sections of the blended films which showed a uniform structure. An interesting phenomenon was observed during the DSC measurements which showed a shift inTgof the blended samples with scanning time. Infrared and thermogravimetric measurements were conducted to further investigate this phenomenon and the results were explained as the change inTgbeing caused by the elimination of water molecules and the formation of anhydrides in the polyacrylic acid portion of the polymer b

ISSN:0021-8995    

DOI:10.1002/app.1988.070360807

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of the pore size on the surface of the water‐wet reverse osmosis membrane and the solvents used in the solvent exchange process on the pore size of the resulting dry cellulose acetate membrane was studied with respect to the separation of a CO2/CH4mixture. It has been found that there is a critical pore size on the surface of wet membrane that results in the smallest pore size on the dry membrane and, consequently, in the highest separation factor. Such critical pore sizes become greater when the boiling point of the second solvent is increase

ISSN:0021-8995    

DOI:10.1002/app.1988.070360808

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractOriginally incompatible blends of SAN 30% and PC 70% were extruded with extremely high shear rate up to 107s−1as a typical example of the blends. The materials were examined with a scanning electron microscope (SEM), a pulsed NMR, etc. The molecular weight of the blends was also measured with gel permeation chromatography. The blends are of binary systems microscopically in the first run of extruding, in which the minor constituent is present as small spherical particles in the major constituent. The apparent volume fraction of the spherical minor constituent estimated from the microscopic photographs decreases with the shear rate. The fraction is decreased also with the repeated runs. SEM observation reveals that dimple fracture of microsize takes place on SAN sphere dispersed in PC matrix. And at the bottom of the dimple, a small particle, which would be composed of PC, is present. From these, SAN in the blend is thought to be partly ductile even at the temperature of liquid nitrogen. At the fifth run, the blend appears uniform or structureless. Dynamic loss tangent gives two peaks corresponding to that of SAN and that possibly attributed to PC. The latter shifts to lower temperatures with the number of extruding run. These show that some of SAN is mixed with PC in a compatible form. The pulsed NMR analysis supports the conclusion. Furthermore, the analysis suggests that some of SAN is mixed in PC. This result shows the compatibility of SAN with PC is enhanced in extremely high shear rate processin

ISSN:0021-8995    

DOI:10.1002/app.1988.070360809

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effects of film formation procedures on transport properties are reported for a rigid‐chained, fluorinated, aromatic polyimide. Residual dimethylacetamide (DMAC) solvent present in films formed under certain casting protocols produces complexities in the permeation behavior of helium and carbon dioxide. Specifically, helium permeabilities are lower, while those of carbon dioxide are higher, in a film containing 8 wt% residual DMAC than in an annealed film containing<1 wt% DMAC. Significant differences in transport properties are also observed between films prepared using two different casting techniques. These differences appear to be due to differences in organization of chain segments within films. The results of this study emphasize the considerable care needed in formation and postformation processing of these materials to ensure optimum flux/selectivity properties in such application

ISSN:0021-8995    

DOI:10.1002/app.1988.070360810

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY