bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of liquid mixtures by using polymer membranes. III. Grafted poly(vinyl alcohol) membranes in vacuum permeation and dialysis
Authors: Shantora V. , Huang R. Y. M. 
Published: April 2003

AbstractA series of poly(vinyl alcohol) membranes were modifed by radiation‐induced graft copolymerization with acrylic acid and methacrylic acid monomers. These grafted poly(vinyl alcohol) membranes were then tested for their separation and permeability characteristics in vacuum permeation and dialysis experiments. The permselectivity of the membranes toward methanol and water was studied on a vacuum permeation apparatus at 30, 40, and 50°C. The permeation process was found to be a temperature‐activated process. The logarithm of the permeation rate varied linearly with the reciprocal of the absolute temperature. The permeability of the grafted membranes was found to increase with the degree of grafting, with no appreciable selectivity toward water in binary mixtures. The acrylic acid‐grafted membranes generally showed greater improvement in permeability than the methacylic‐grafted membranes. The permeability of the grafted membranes toward methanol, sodium chloride, urea, creatinine, and uric acid was studied in a dialyzer. In all cases, the grafted membranes showed an improved permeability toward these solutes over the commercial poly(vinyl alcohol) membranes. The dialysis results were then compared with those obtained for dialysis‐grade cellophane membranes. For the case of sodium chloride, urea, and methanol, the permeability of the grafted membranes was comparable to that of cellophane. A comparison of commercial and grafted poly(vinyl alcohol) membranes in their permeability toward ionic solutes exhibited somewhat anomalous behavior in that the permeability of the commercial membranes was higher than that of the grafted membranes. This related to the ionic nature of the modified membrane. The permeability coefficients determined in the dialysis experiments were found to be directly related to the degree of hydration of the grafted membrane. This behavior was attributed to changes in the size and shape of voids within the membrane structure.
Analysis of the impurities in industrial ε‐caprolactam. Hypothesis of formation
Authors: Jodra L. G. , Romero A. , García‐Ochoa F. , Aracil J. 
Published: April 2003

AbstractAnalysis of an industrial ε‐caprolactam by gas–liquid chromatography has been carried out using different stationary phases and operating conditions. The impurities in the ε‐caprolactam are identified and hypotheses about their formation are presented. In some cases the presence either in cyclohexane or cyclohexanone of the possible impurity‐producing compounds is shown.
Solution spinning of a semirigid chain polymer forming ultrahigh modulus fibers
Authors: Valenti B. , Alfonso G. C. , Ciferri A. , Giordani P. , Marrucci G. 
Published: April 2003

AbstractSingle filaments of the polyterephthalamide of p‐aminobenzylhydrazide (X‐500) were prepared by spinning X‐500 solutions in dimethyl sulfoxide (DMSO) using water as a coagulating agent. The polymer is known for its ability to develop ultrahigh modulus fibers and for having a semirigid chain conformation with a persistence length of ∼50 Å in DMSO. In the latter solvent, molecular rigidity appears to be just below that required for spontaneous formation of a nematic phase. The orientation of the fibers was performed in three different stages: during coagulation (I), in the washing bath following coagulation (II), and during postspinning treatments (III). Corresponding mechanical properties were determined. The results indicate that high elastic modulus (15 GPa) already appears during step I at very moderate pulloff ratios. Therefore, considerable orientation had already occurred in the flowing solution. Further increase of fiber orientation yields a large increase of modulus (from 22 to 67 GPa) during solid‐state deformation (step III). The orientation of the flowing solution was monitored by viscosity and birefringence measurements. The results are discussed in terms of orientation due to elongational and shear flow and, possibly, a flow‐induced transition to a nematic phase in the concentrated solution in which chain entanglement is shown to occur.
The formation and structure of suspension‐polymerized styrene–divinylbenzene copolymers
Authors: Howard G. J. , Midgley C. A. 
Published: April 2003

AbstractPorous polymers were prepared by suspension copolymerization of styrene/divinylbenzene in various ratios together with various quantities of diluents, both solvating and nonsolvating. Parallel bulk polymerizations were made to detect the onset of gelation and phase separation. The dry polymeric beads were examined by a range of techniques: apparent densities; mercury porosimetry; nitrogen sorption/desorption isotherms, vapor sorption, equilibrium swelling, and electron microscopy. The properties of the porous polymers are discussed in terms of phase separation during polymerization consequent on either an unfavorable polymer–solvent interaction or a microsyneresis.
Mechanical properties of borate crosslinked poly(vinyl alcohol) gels
Authors: Cheng A. T. Y. , Rodriguez F. 
Published: April 2003

AbstractBoric acid does not introduce crosslinks in poly(vinyl alcohol) solutions, but gelation does occur in the presence of cations. In this experimental study, the dynamic mechanical properties of these gels were determined using test‐tube torsion pendulums and an air‐bearing torsion pendulum. The modulus at a fixed concentration of polymer and boric acid increases with increasing sodium ion concentration up to the point where the atom ratio of sodium to boron reaches 1. Higher sodium concentrations do not increase the modulus. The log decrement, on the other hand, decreases with increasing sodium concentration continuously without reaching a plateau at the equal atom ratio. Log decrements as low as 0.02 can be measured. The storage modulus depends on the logarithm of borate concentration and on the 4.7 power of poly(vinyl alcohol) concentration. Only a very small portion of the borates in solution take part in effective crosslinks. The activation energy for breaking individual bonds in a function of temperature and the cation to boron ratios. At a fixed cation concentration, this activation energy is more negative with increasing amount of boron ions due to a transformation of monomeric crosslinks into polymeric crosslinks, so that the storage modulus which measures crosslink density decreases as a temperature rises.
Graft copolymerization of vinyl monomers on modified cottons. XVIII. Grafting of methyl methacrylate and acrylonitrile on cotton treated with N‐methylol crosslinking agents using tetravalent cerium as initiator
Authors: Hebeish A. , El‐Rafie M. M. , El‐Kashouti M. A. , El‐Sisi F. 
Published: April 2003

AbstractCeIV‐induced grafting of methyl methacrylate and acrylonitrile on cotton fibers crosslinked with dimethylol ethylene urea, dimethylol dihydroxyethylene urea, and dimethylol carbamate was investigated. The graft yields obtained with crosslinked cotton were signifcantly lower than the untreated cotton, irrespective of the crosslinking agent and the monomer used. However, the extent and rate of grafting depended upon the degree of crosslinking and the nature of monomer. Based on the magnitude of grafting and CeIV consumption during grafting and oxidation of the untreated and crosslinked cottons, the different reactions occurring during grafting of vinyl monomers on these modified cottons were elucidated.
The accessibility of sulphonic acid groups in basic dyeable polyester fibers. I. The prevention of fiber hydrolysis during dyeing
Authors: Ingamells W. , Lilou S. H. , Peters R. H. 
Published: April 2003

AbstractThe rate of acid hydrolysis of a basic dyeable polyester in water, before and after heat‐setting, has been investigated. Intrinsic viscosity measurements and chemical analysis have been used to establish experimental conditions under which the hydrolysis is inhibited. It is suggested that the critical stage of the hydrolysis mechanism is the exchange of sodium ions from the sulphonate groups in the fiber for hydrogen ions.
Synthesis of phosphorus‐containing wofatit cation exchangers and their affinity toward selected cations
Authors: Bogoczek Romuald , Surowiec Joanna 
Published: April 2003

AbstractA number of solid Cationits have been prepared derived from WofatitTrademark, VEB Chemiekombinat Bitterfield.
gel and canal structures: styrene/DVB, chloromethylated ST/DVB, and acrylic acid/DVB copolymers. To functionalize the copolymers, PCl3/AlCl3 and dialkyl phosphites or trialkyl phosphites were used. The influence of the polymer matrix structure and the chemical structure of the functional groups of obtained Ionits on their affinity toward 23 metallic cations in acidic media has been investigated using the conductivity method. To obtain comparison data, commercial “Wofatit”–sulfonic and–carboxylic Cationits, have been tested under identical conditions.
Viscoelastic properties of the model system: Epoxy resin–glass beads–poly(buthylmethacrylate)
Authors: Lipatov Yu. S. , Rosovizky V. F. , Shifrin V. V. 
Published: April 2003

AbstractTemperature dependences of viscoelastic characteristics for a model system epoxy resin–glass beads covered with poly(buthylmethacrylate) were studied. The formation of interphase region was established with its own relaxation maximum. The structure of this region is supposed to be a kind of semi‐interpenetrating network formed by crosslinked and linear polymers. Using the Gordon–Taylor equation, the volume fractions of both polymeric components in the interphase region were calculated. An experimental evidence in favor of theoretical calculations has been obtained showing some increase in the glass transition temperature of a two‐phase polymeric system by introducing small amounts of the component with a lower glass temperature as compared with this temperature for the main component.
Relationship between viscoelastic properties and gelation in thermosetting systems
Authors: Tung Chiang‐Ying M. , Dynes Paul J. 
Published: April 2003

AbstractA method is described for determining from dynamic viscoelastic data the gel time of thermosetting resins. Gelation of nine systems including epoxies, acetylene‐terminated sulfone, and silicones was correlated with the crossover of the dynamic storage G′ and loss G″ moduli measured during isothermal curing. The effect of measurement frequency on gel time is discussed and related to the standard gel test. A lower temperature limit for the valid aplication of this technique was found to be at T > Tgg + 30°C, where Tgg is the glass transition of the system at the gel point.
Interdependence of structure and properties in segmented polyurethanes
Authors: Foks J. , Janik H. , Winiecki S. 
Published: April 2003

AbstractOn the basis of Clough and Schneider's studies, who investigated segmented polyurethanes with the use of DSC, we assumed that warming may lead to morphological changes in these compounds. We warmed polymers for 10 h in argon atmosphere at 130°. Morphological changes occurring in polyurethanes at a modified temperature were confirmed with an electron microscope and were found to affect to a high degree the mechanical properties of the polymer investigated.
Effect of hygrothermal fatigue on dynamic mechanical properties of glass‐reinforced polyesters
Authors: Mijović Jovan 
Published: April 2003

AbstractSeveral nonreinforced and reinforced crosslinked polyester formulations were prepared and investigated. Solid glass microspheres, with and without coupling agent, were used as reinforcement. All samples were exposed to various cyclic hygrothermal fatigue patterns, differing from one another by the temperature and duration of a cycle. Dynamic mechanical measurements were used to evaluate the effect of hygrothermal fatigue on the mechanical properties of all formulations. Fatigue induced changes in the glass–matrix interphase led to the appearance of relaxation peaks (β′ and β″) in the temperature range between −50°C and −10°C. Electron microscopic evidence was obtained for the existence of nodular morphology on all fracture surfaces. The character of nodular morphology was described in terms of an inhomogeneous thermoset network.
Characterization of penetrant interactions in Kapton polyimide using a gravimetric sorption technique
Authors: Iler L. R. , Laundon R. C. , Koros W. J. 
Published: April 2003

AbstractSorption of pure anhydrous ammonia and pure sulfur dioxide in Kapton polymide has been measured at 30 and 35°C at subatmospheric pressures using a McBain quartz spring balance. The sulfur dioxide sorption and desorption was well described by the Fickian transport model; however, the ammonia sorption exhibited significant deviations from Fickian behavior. A substantial fraction of the initially sorbed ammonia remained in the film after extended periods under vacuum at 35°C. Infrared analysis of the treated film revealed the presence of new carbonyl and nitrogen–hydrogen stretching peaks characteristic of primary and secondary amides. These observations suggest that the ammonia reacts chemically with some of the imide linkages. Based on infrared analysis of the ammonia‐exposed Kapton, heating the sample under vacuum at 120°C caused re‐formation of most of the orginally disturbed imide structures, with attendant evolution of ammonia as a condensation product.
Polyurethane synthesis reactions in asphalts
Authors: Bukowski Andrzej , Grętkiewicz Jacek 
Published: April 2003

AbstractA series of asphalt–polyurethane composites was prepared by means of polyurethane synthesis in asphalt and carried out in melt. The applied materials were asphalts of differentiated group components content, polyester polyols of chain structure from linear to strongly branched, 2,4‐tolylene diisocyanate, 4,4‐methylenebis(phenyl isocyanate), and tinorganic catalyst. The asphalt components react with isocyanates to a minimal degree. The influence of the applied substrates, temperature, and polyurethane content in the system on the basic kinetic relations characterizing the process is presented. Polyurethane synthesis in asphalts does not differ in a fundamental way from the obtaining of polyurethanes, especially when their content in the composition is significant, 20 wt % and more.
On the factors governing the pressure dependence of the viscosity of moderately concentrated polymer solutions
Authors: Geerissen H. , Schmidt J. R. , Wolf B. A. 
Published: April 2003

AbstractViscosity measurements were carried out as a function of pressure and temperature with solutions of polystyrene in eight (endothermal) θ‐solvents at the respective critical composition by means of a Searle‐type apparatus. A rolling‐ball viscometer was used for the investigation of the pure solvents. In all cases the viscosity coefficient increases in a more or less exponential manner when the pressure is raised. For θ‐conditions, the volumes of activation of the solutions exceed that of the pure solvent by typically 10–15%. The exact amount of this extra efffect stemming from the presence of the polymer and its variation with temperature can be qualitatively correlated with the heats of mixing. The ratio of the viscosity of the solution at 1000 and 1 bar, respectively, can be varied for a given solvent power (θ‐temperature) by the choice of the solvent from ca. 2 (cyclopentane) to 4 (trans‐decalin). Within a given system, the maximum effects that can be realized by a change of the solvent power via the variation of temperature ranges from ca. 3 to 6 (tert‐butylacetate).
Gas permeabilities of cellulose nitrate/poly(ethylene glycol) blend membranes
Authors: Kawakami M. , Iwanaga H. , Hara Y. , Iwamoto M. , Kagawa S. 
Published: April 2003

AbstractThe permeability (P) of cellulose nitrate (CN)/poly(ethylene glycol) (PEG) blend membranes for N2, O2, and CO2 has been measured as a function of film composition. The system CN/PEG‐300 showed excellent miscibility, and films of the composition from 100/0 to 50/50 could be used for permeability measurements. P for each gas has been found to be almost constant or rather slightly lowered up to ca. 20 wt % PEG‐300 content and then increased appreciably with increasing fraction of PEG. The increment of permeability was most remarkable for CO2, and hence the permselectivity for CO2 was considerably enhanced. Such a behavior of P has been found to be attributable to the plasticizing effect of PEG molecule lowering the glass transition temperature of the blend polymers. The effect of the molecular weight of PEG and that of closed voids generated in glassy blend membranes fabricated from acetone cast on gas permeabilities have been also discussed.
Modification of the fine structure of cellulose by halogen and heat treatments
Authors: Lewin Menachem , Guttmann Hilda , Derfler David 
Published: April 2003

AbstractTreatment of various celluloses such as cotton, sulphite, and sulphate pulp with bromine water brings about profound changes in the fine structure of the fiber. Depending on the conditions of the treatment and on the nature of the cellulose, increases or decreases in the accessibility of the cellulose are observed, indicating crystallization and decrystallization processes. In the case of bleached sulphate pulp, similarly to rayon previously studied, an initial decrystallization proceeds the crystallization step. These changes were determined by the IR method, which was correlated previously to the bromine accessibility method. They are accompanied by highly significant changes in moisture absorption. The crystallization proceeds according to first‐order kinetics with respect to the concentration of the less‐ordered regions (LOR) of the cellulose. The rates of crystallization for the various celluloses varied in a range of 4 orders of magnitude. The activation energies of the bromide induced crystallization were found for all celluloses to be in the range of 10–15 kcal/mol, as compared to 30–40 kcal/mol obtained upon crystallizing the same celluloses by heating in the temperature range of 180–200°C. These values correspond to those of solvent and thermal crystallizations of poly(ethylene terephthalate), indicating the similarity between the crystallization mechanisms of the two polymers.
Thermal characteristics of poly(ethylene terephthalate) fiber grafted with poly(vinyl acetate) and poly(vinyl alcohol)
Authors: Faterpeker S. A. , Potnis S. P. 
Published: April 2003

AbstractPoly(ethylene terephthalate) (PET) fibers were grafted with poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVA). The effects of graft copolymers PVAc and PVA on morphological properties of PET were evaluated by differential thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. Melting temperature, heat of fusion, and mass fractional crystallinity of PET was not affected by graft PVAc and PVA. No individual glass transition and melting points corresponding to the graft PVAc and PVA were observed, indicating thereby that graft copolymer mainly exists in the form of free chains inside the PET matrix. Poly(vinyl alcohol) graft copolymer degraded at much lower temperatures than poly(vinyl alcohol) in powder form. Thermal stability of PET fiber was not affected by graft PVAc, where as PET–g–PVA showed an additional degradation point at 360°C.
Temperature dependence of surface crystallization in bimorphic PET fibers
Authors: Durning C. J. , Scott M. G. , Weigmann H.‐D. 
Published: April 2003

AbstractOpen‐bath, organic liquid treatments may be used to produce high surface area PET fibers through the action of liquid solvent‐induced crystallization (SINC). It has been found that as the treatment bath temperature is increased, surface modification suddenly disappears. For a particular treatment method this occurs at a reproducible temperature, well below the liquid boiling point. A qualitative understanding of the mechanism of surface cavitation during liquid SINC is developed based on current descriptions of the component processes involved. These processes are: the glass–rubber transition, diffusion through rubbery and glassy polymer, and polymer–diluent crystallization. Although calculations of the threshold concentration for swelling support this conceptual framework, the absence of surface cavitation at higher treatment bath temperatures is not explained by it and is therefore attributed to an intervening phenomenon. Analysis of penetration depth data together with surface microscopy suggest the formation of a smooth surface layer interfering with normally observed cavitation at elevated temperatures. Manipulation of the extent of vapor precontact shows that vapor SINC prior to liquid exposure is most likely responsible for the smooth layer.
Photo‐induced graft copolymerization. III. Graft copolymerization of methyl methacrylate onto cellulose using peroxydiphosphate as photoinitiator
Authors: Lenka Subasini , Nayak Padma L. 
Published: April 2003

AbstractPhoto‐induced graft copolymerization of methyl methacrylate onto cellulose was investigated using peroxydiphosphate ion as the photoinitiator. The percentage graft yield increases with increasing both the monomer and initiator concentration. The reaction was carried out at three different temperatures, and the overall activation energy was computed. The kinetic data and other evidence indicate that the overall polymerization takes place by a radical mechanism. A suitable kinetic scheme has been suggested.
Studies on dyeing and mechanical properties of nylon 6 filaments subjected to swelling treatments
Authors: Subramanian D. R. , Venkataraman A. , Bhat N. V. 
Published: April 2003

AbstractDrawn nylon 6 filaments were subjected to swelling treatment with benzyl alcohol and aqueous solution of phenol and formic acid under slack condition and under tension. The pretreated samples were dyed with a disperse dye Foron Yellow SE‐FL (C.I. Disperse Yellow 42). A considerable increase in the equilibrium dye uptake was observed as a result of swelling treatment. Studies on lateral order by X‐ray methods showed that lateral order has increased considerably as a result of preswelling treatment. This apparent contradiction, viz., increase in lateral order and at the same time increase in dye upstake, is explained as due to increased void volume. Studies on mechanical properties showed that the percentage elongation is increased as a result of swelling treatment under slack condition in spite of increased lateral order. This is explained as due to the slippage of chain‐folded crystallites.
Investigation of cure in epoxy resins: Ultrasonic and thermally stimulated current measurements
Authors: Bunton Lesley G. , Daly John H. , Maxwell Ian D. , Pethrick Richard A. 
Published: April 2003

AbstractAcoustic and thermally stimulated current measurements are reported as a function of cure for dicyanodiamide cured epoxy resins. It is found that the acoustic propagation is dominated by the generation of voids and does not directly reflect the extent of cure. In contrast, the thermally stimulated data correlate well with conductivity data, the amplitude of the space charge peak decreasing with increasing degree of cure and the dipole peak shifting to high temperatures as predicted from DSC data. Both methods exhibit potential as NDT methods for cure in resins.
Spontaneous adhesion of silicone rubber
Authors: Gent A. N. , Vondráček P. 
Published: April 2003

AbstractLightly crosslinked silicone rubber has been found to bond spontaneouly to polar substrates and to itself. The strength of adhesion increases linearly with time, eventually reaching the fracture strength of the rubber. The process is accelerated by raising the temperature (activation energy ⋍ 60 kJ/g. mol), by the presence of moisture, and by ammonia vapor. It is tentatively attributed to hydrolytic decomposition of the polymer leading to the formation of reactive groups which interlink with surface groups, probably hydroxyls, on polar substrates, or with each other in the case of selfadhesion.