bluuebunny/crossref_metadata_2025_split huggingface dataset:
Graft copolymerization of acrylonitrile onto jute fibers (studies on Ce(IV)‐hippuric acid redox system)
Authors: Patnaik S. , Sarangi S. , Mohanty A. K. , Singh B. C. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile (AN) onto chemically modified bleached jute fibers was studied using Ce(IV)‐hippuric acid redox initiator system. The effects of time, temperature, concentration of monomer (AN), metal ion (Ce4+), hippuric acid, sulfuric acid, and amount of jute fiber on graft yield have been studied. The effects of some organic solvents and inorganic salts on graft yield have also been studied. Infrared spectra of chemically modified bleached jute and grafted jute have been taken and their characteristic bands have been identified. More than 90% graft yield could be achieved with the present system.
FTIR study on structural transformation of keratin films induced by stretching
Authors: Koga Joichi , Kawaguchi Kiyohiko , Nishio Etsuo , Joko Kyohei , Ikuta Nobuo , Abe Ikuo , Hirashima Tsuneaki 
Published: April 2003

AbstractFourier transform infrared spectroscopy (FTIR) was employed to explore the structural transformation by stretching of the film composed of a keratin derivative. The derivative was prepared by S‐carboxymethylation of the low‐sulfur keratin of wool. The cast film was stretched to different ratios in ethanol/water (7:3 v/v). The amide infrared absorption bands of the derivative were changed by stretching the film. Curve analysis was undertaken to estimate the contribution of each peptide conformation to the amide II band at each stretching. The analysis shows that the stretching mainly causes the structural transformation from random coil to β‐structure. Moreover, a transient state arises in the course of the transformation. In such a state, the part of random coil increases while that of β‐structure decreases. The infrared dichroism of the film also supports the existence of the transient state. On curve analysis, only the α‐structure was found to reverse the dichroism of the amide II band in the transient state. This result suggests that the crystalline phase of α‐structure is rearranged. Such rearrangement results in inhibition of the transformation from random coil to β‐structure.
Diffusion mechanism of direct dyes into a cellulose membrane: The structural effect of direct dyes on the adsorption rate
Authors: Maekawa Masako , Udaka Masako , Sasaki Mika , Tujii Yasuko , Yoshida Hiroyuki , Kataoka Takeshi , Nango Mamoru 
Published: April 2003

AbstractThe transport of three typical direct dyes, C.I. Direct Yellow 12, C.I. Direct Red 2, and C. I. Direct Blue 15, into a cellulose membrane has been studied at 55°C. Sodium chloride was used as a stimulator for dyeing. The effects of the concentration of the stimulator on the adsorption isotherms, the adsorption rate, and the concentration profiles in the membrane were tested. The experimental adsorption rates of three dyes were quite different. The diffusion mechanism of the dyes into a cellulose membrane was analyzed on the basis of the parallel transport equation of surface and pore diffusion as developed in our previous paper. The experimental uptake curves showed good agreement with the theoretical curves for surface diffusion control. Experimental concentration profiles also agreed reasonably well with the theoretical lines for surface diffusion control rather than pore diffusion control. The surface diffusivities of three dyes were quite different and nearly independent of the adsorbed phase concentration of the dye.
Multiphase materials with lignin. IV. Blends of hydroxypropyl cellulose with lignin
Authors: Rials Timothy G. , Glasser Wolfgang G. 
Published: April 2003

AbstractPolymer blends of hydroxypropyl cellulose (HPC) and organosolv lignin (OSL) were prepared by mixing in solutions of both pyridine and dioxane, and casting as films, and by mixing in the melt followed by extrusion. All preparations exhibited partial miscibility as evidenced by a single Tg up to a composition of 40 wt % lignin above which phase separation was detected. Dioxane‐cast and injection‐molded blends were distinguished from the pyridine‐cast materials by a positive Tg deviation from additivity, an approximation which adequately described the latter. This positive deviation in Tg is attributed to the formation of a liquid‐crystal mesophase with a resultant reduction of amorphous HPC available for interaction with the lignin component. This explanation is supported by a rapid rise in modulus (∼150%) and tensile strength with very low lignin content, and by an associated sharp decline in ultimate elongation. The development of morphological features, as observed by scanning electron microscopy provide further substantiation of this hypothesis.
Properties of networks obtained by internal plasticization of epoxy resin with aromatic and aliphatic glycidyl compounds
Authors: Misaki Toshikazu , Hirohata Takeshi , Yoshii Minoru , Hamasaki Takehiko 
Published: April 2003

AbstractIn order to improve the fracture properties of p, p′‐diaminodiphenylmethane‐cured epoxy resin, various kinds of aromatic and aliphatic glycidyl compounds were investigated as a modifier at an amount of 30 wt %. Several compounds promoted the fracture toughness. In any glycidyl compounds, however, heat resistance was decreased by the modification. The dynamic mechanical properties of the modified epoxy resins were measured. The crosslinking density ρ was calculated from the theory of rubber elasticity, and the mechanical properties of the resins were discussed in regard to the crosslinking density. Tensile strength was scarcely affected by the crosslinking density. Elongation at break and Izod impact strength increased remarkably with decrease in crosslinking density. The fracture toughness KIc‐ increased with decrease in crosslinking density except at small ρ.
Effect of K‐value on the tensile yield properties of poly(vinyl chloride)
Authors: Havriliak S. , Shortridge T. J. 
Published: April 2003

AbstractTensile measurements were made on milled compression molded test specimens of PVC of different K values from strain rates of 0.0001–0.1 s−1 and temperatures of −40 to 25°C. The dependence of yield stress on temperature and strain rate was treated in terms of the Ree–Eyring model as proposed by Roetling for poly(methyl methacrylate) and Bauwens‐Crowet et al. for poly(vinyl chloride). The data reduction was achieved using sophisticated and unbiased statistical techniques that not only provided parameter estimates but their confidence intervals. The yield stress parameters for the alpha and beta processes were found to be independent of K value and within experimental error the same as those reported by Bauwens‐Crowet et al. The activation energy for the beta process from these yield stress studies (15.1 ± 0.3 kcal) is within experimental error the same as that determined from viscoelastic measurements (14.1 ± 1.2 kcal) reported by the authors. This observation supports the contention that beta process in the viscoelastic and yield stress measurements are closely related mechanisms.
Engineering plastics from lignin. XVII. Effect of molecular weight on polyurethane film properties
Authors: Kelley Stephen S. , Ward Thomas C. , Rials Timothy G. , Glasser Wolfgang G. 
Published: April 2003

AbstractA series of five fractions with number average molecular weights (M̄n) between 1500 and 10,000 daltons were isolated from a Kraft hydroxypropyl lignin (HPL). From 1H‐NMR and UV analysis the chemical properties of the HPLs were found to vary slightly with molecular weight. The hydroxyl content decreased while the glass transition temperature (Tg) increased as the HPL molecular weight increased. The Fox‐Flory equation adequately described the M̄n vs. Tg relationship. The HPL fractions were used as polyols for the preparation of solvent‐cast polyurethane networks (PU) in film form. The Tg of the PUs increased from 40° to 120°C as the M̄n of the polyol rose from 1500 to 10,000 daltons. The molecular weight between crosslinks (M̄c) of the networks was determined by swelling. An observed decrease in M̄c with an increase in M̄n was related to the functionality of the system. The strength properties of films prepared from fractionated HPLs were superior to those prepared from nonfractionated HPLs.
Molecular weight distribution of cellulose as its tricarbanilate by high performance size exclusion chromatography
Authors: Evans Robert , Wearne Ross H. , Wallis Adrian F. A. 
Published: April 2003

AbstractCellulose tricarbanilates (CTCs) were prepared from a range of cellulose samples (cotton linters, wood pulps, Avicel, amorphous cellulose, and cellulose II) for molecular weight distribution (MWD) studies by high performance size exclusion chromatography (HPSEC). The HPSEC columns were calibrated using CTC standards with the aid of a microcomputer. CTCs were prepared by reaction of cellulose samples with phenylisocyanate in pyridine at 80°C. For some samples, e.g., cellulose II, activation with liquid ammonia and pyridine was necessary prior to reaction in pyridine. All samples tested were also derivatised in dimethylsulfoxide at 70°C, although for high molecular weight (MW) cellulose samples some MW reduction occurred in this solvent. Conditions were determined for optimum precipitation of CTCs in aqueous methanol without coprecipitation of low MW impurities.
Molecular weight distribution in continuous stirred tank vinyl acetate emulsion polymerization
Authors: Lee Chan H. , Mallinson Richard G. 
Published: April 2003

AbstractEmulsion polymerization typically produces polymers of high molecular weight with broad distributions of molecular size. Many models have been proposed that use either a Flory type distribution, resulting in a polydispersity of two, or a distribution function to represent the breadth of the distribution. In this work, a model for the distribution of molecular weights is derived as a approximation from a detailed molecular weight model that was previously developed. The model is found to approximate the distribution of molecular weights well for several emulsifier concentrations is continuous stirred tank emulsion polymerization of vinyl acetate. An analysis is also conducted of the transformation of gel permeation chromatography data to weight and number fractional distributions of the molecular sizes.
Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. II. The permselectivity of chitosan membrane
Authors: Mochizuki Akira , Sato Yoshio , Ogawara Hisashi , Yamashita Shuzo 
Published: April 2003

AbstractThe separation of water/alcohol mixtures through chitosan membrane was investigated. The degree of the deacetylation of chitosan did not affect the selectivity of the membrane in the separation of the water/ethanol mixture. The selectivity of the chitosan membrane was affected by the specific salts such as CoSO4, ZnSO4, and MnSO4 and it increased when the salts were present in the feed mixture or the membrane was pretreated with the salt solution. This behavior would be explained by the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of chitosan molecule due to the formation of complexes with metal ions.
The structure of organosilicon plasma‐polymerized coatings on metal substrates
Authors: Coopes I. H. , Griesser H. J. 
Published: April 2003

AbstractThe structure of coatings formed by the low pressure plasma‐polymerization of hexamethyldisiloxane has been studied by FTIR and XPS techniques. The coatings were performed in two pressure regions: 0.63–0.88 and 0.36–0.44 torr. At both pressures much of the structure of the monomer appeared to be maintained. Coatings deposited at the higher pressure showed the expected increase in abstraction of methyl groups and formation of Si  O  Si crosslinks with increasing discharge power. The lower pressure coatings showed a markedly more diverse pattern of peaks associated with Si  O bonds. The spectra of the moncmer, hexamethyldisiloxane, and of a highly crosslinked silicone resin were examined in order to clarify the way in which FTIR spectra varied during the polymerization and crosslinking processes. The different structures observed emphasize a considerable potential for tailoring structure by varying deposition conditions.
Water sorption in polyamide–imide films and its effect on dielectric loss
Authors: Tchangai T. , Segui Y. , Doukkali K. 
Published: April 2003

AbstractWater sorption and diffusion has been measured in polyamide–imide over a range of temperature and relative humidities. The results are compared to those obtained on Kapton and discussed in terms of chemical differences between these two materials. Changes in dielectric loss during hydrothermal aging under 85°C and 85% RH have been measured. These changes are correlated to the water sorption kinetics.
Preparation and properties of soluble and colorless fluorine‐containing photoreactive polyimide precursors
Authors: Omote Toshihiko , Yamaoka Tsuguo , Koseki Kenichi 
Published: April 2003

AbstractPhotoreactive polyimide precursors, which are readily soluble in common organic solvents and optically transparent at light of 365 nm wavelength (i‐line), similar to aliphatic polyimide precursors, were obtained by polycondensation of biphenyltetracarboxylic dianhydride (BPDA) and fluorine‐containing diamine compounds. In particular, the polyimide precursor prepared from 2,2 bis(3‐amino‐4‐methylphenyl) hexatluoropropane showed high solubility in common organic solvents and complete transparence at i‐line wavelength. A 3 μm thick film of the polyimide precursor on a silicon wafer was exposed and developed, and offered high resolution (0.5μm line) patterns with an aspect ratio of 6.0. This polymide precursor swells very little in the developing solvent, resulting in the high resolution. Conversion of polyamic acid to polyimide at several curing temperatures was observed by infrared spectrophotometer and thermogravimetry.
Branched and linear polyethyleneimine supports for resins with retention properties for copper and uranium. VII
Authors: Rivas B. L. , Maturana H. A. , Catalán R. E. , Perich I. M. 
Published: April 2003

AbstractWeak and strong basic resins were synthesized by crosslinking with 1,7‐dibromoheptane and 1,12‐dibromododecane and subsequent N‐methylation reaction of branched and linear polyethyleneimine. All the resins are insoluble in water. It was found that the N‐methylated resins showed the highest retention ability for uranium. The resins do not retain significatively iron (> 10%), and only two of them retain copper above 80% at optimum pH. Elution assays with sulphuric acid, sodium carbonate, and thermal stability were also carried out.
Plasma‐induced polymerization
Authors: Epaillard F. , Brosse J. C. , Legeay G. 
Published: April 2003

AbstractLow vapor tension polymerized acrylates as thin films when they are subjected to a cold plasma. The plasma‐induced polymerization is described in terms of direct or indirect energy transfer from the plasma to the monomer. The indirect transfer is related to the absorption of UV‐visible radiations by the monomer. The radiations are emitted from excited species of the plasma. Direct transfers correspond to the reactive species collision (radicals, ions metastable species) with a molecule of monomer. The polymerization is a result of these two kinds of transfers. Direct transfers lead to competitive reactions (addition, terminations and degradation, etc.) and acrylate polymerization is mostly induced by the UV‐visible radiations.
Influence of cations and borate on the alkaline extraction of xylan and glucomannan from pine pulps
Authors: Scott Ralph W. 
Published: April 2003

AbstractSouthern pine pulp fibers were extracted with Na, K, and Li hydroxides at several concentrations from 0.5 to 4.0 m (molal). The amounts of extracted xylan and glucomannan increased with the swelling of the cellulose structure up to 2.0–2.5 m. The addition of H3BO3 to alkaline solutions produced the B(OH) anion, which had less swelling power than OH−. It was not effective for removal of xylan except for some very accessible xylan of holocellulose. Removal of xylan from chemical pulps depended upon OH− in molar excess over H3BO3. In the same extractions, glucomannan removal was enhanced by B(OH) alone and further increased by additional OH−. The formation of anions (carboxylate in xylan and borate complex of glucomannan) appeared to be important for the release of polymer from within the cellulose structure. Some glucomannan was more accessible in oxygen pulp than in holocellulose. The resorbed xylan of kraft pulp was less accessible than the xylans of either holocellulose or oxygen pulp.
Bending‐beam study of water sorption by thin poly(methyl methacrylate) films
Authors: Tong H. M. , Saenger K. L. 
Published: April 2003

AbstractA bending‐beam technique has been employed to study the effects of film thickness (7–55 μm) and rate of cooling during film preparation (∼ 6°C/h to a dry ice quench) on sorption characteristics of water by poly(methyl methacrylate) films coated on thin fused quartz beams (˜ 84 μm thick). In each experiment, the curvature of a polymer coated beam exposed to liquid water was monitored as a function of time by a low power laser pointer. With the use of a transport model which considers the sorption process as the linear superposition of contributions from Fickian diffusion and a first‐order polymer molecular relaxation process, the beam curvature data were analyzed to determine the governing transport kinetics and associated transport parameters such as water diffusion coefficient and relaxation rate constant. From curvature analysis for thin films (7–13 μm in thickness), it was found that water diffusion proceeds at early times in a Fickian‐like manner with a diffusion constant of 2–4 × 10−9 cm2/s. At later times, significant relaxation contributions lead to non‐Fickian diffusion behavior, an effect that is more pronounced as the film thickness or sample cooling rate decreases. In addition, sorption of water was found to reduce the film stress (initially tensile at ˜ 108 dyn/cm2) at a rate that increases with sample cooling rate. The high initial film stress not present in free‐standing films may account for the relatively higher diffusion coefficient (∼ 2 × 10−8 cm2/s) found here for very thick (55 μm) PMMA coatings. Because the bending‐beam technique uses coated samples, it is especially well suited for studying penetrant transport into polymer coatings.
The effect of γ radiation on the physical structure and mechanical properties of ultrahigh molecular weight polyethylene
Authors: Birkinshaw C. , Buggy M. , Daly S. , O'neill M. 
Published: April 2003

AbstractUltrahigh molecular weight polyethylene has been irradiated using a cobalt 60 source to give received dose between zeor and 50 Mrad. Irradiacted specimens were subjected to tensile characterization, dynamic mechanical analysis, and differential scanning calorimetry. Changes in tensile and dynamic mechnaical properties following irradiation arise from both molecular rearrangement and from increased crystallinity following scissionof long interlamella tie chains. The effects of post‐irradiation aging on mechanical properties are associated with increasing crystallinity resulting from decomposition of metastable groups formed in the amorphous region during irradiation. Irradiated materials have been subject to sinusoidal stressing between 0.275 and 0.55 of yield stress for 100,000 cycies, and changes in mechnaical and physical properties measured. Increased resistance to creep during stressing was observed with the irradiated materials, behavior which is consistent with previsouly observed changes in crystallinity and crosslink density. Overall property changes measured following stressing were small compared with those induced by the initial irradiation.
Magnetic filed effect on sensitized photocrosslinking reaction of azidomethylated polytsyrene
Authors: Morita Hiroshi , Uchino Noriaki , Nakamura Yasuhiro , Yamaoka Tsuguo 
Published: April 2003

AbstractCharacteriscs curves for the lithographic sensitivity of poly(styrene‐co‐vinylblenzyl azide) (AZMA) with such sensitizer as 2,4‐diisopentvlthioxanthone (DITX), 2‐chlorothioxanthone (CTX), and Michier's ketone wer emeasured in the basence and in the presence of a magnetic filed. By the application of a magnetic field, the get fraction increases, and efficiency of photocrosslink formation increases by ≈ 45% (at 0.1 T) for AZMA/DITX and by ≈ 20% (at 0.5 T) for AZMS/CTX. Senstization mechanism was investigated by measuring UV, IR, and FT‐IR spectra, and AZMS is found to be sensitized effectively by DITX and CTX through the triplet energy transfer, and to produce the triplet nitrene as an intermediate. The magnetic field effect on photocrosslink formation of AZMS/sensitizer systems is interpreted in term of the radical pair model of intermediate species which is formed by hydrogen abstraction of the nitrene from the sensitizer.
HPLC determination of the pore distribution and chromatographic properties of cellulosic textile materials
Authors: Grünwald Michael , Burtscher Eduard , Bobleter Ortwin 
Published: April 2003

AbstractHPLC columns packed with cellulosic textile materials as stationary phase were examined with respect to their chromatographic parameters. The interaction of the stationary phase with water‐soluble substances (mainly textile chemicals) was also studied. The size‐exclusion effects of the porous material were measured for molecules with MW 20−2 × 106, thus giving further information concerning structural changes during the pretreatment of textile materials. Electrostatic and sorptive interactions were detected simultaneously, but found to exert a minor influence. Using a recently developed mathematical model, the pore volume distribution of swollen celluose could be determined from the size‐exclusion data without the introduction of empirical factors. The applied HPLC method of characterizing cellulosic materials offers an alternative to the previously utilized static and chromatographic methods, especially for studies on pretreated textile materials.
Molecular size and solvation of low molecular weight poly(ethylene oxide) and phenol–formaldehyde resols in different solvents
Authors: Riedl Bernard , Vohl M.‐J. , Calvé Louis 
Published: April 2003

AbstractSeveral solvent systems are presently used to characterize the molecular weight of phenol–for‐maldehyde resins. However, results reported in the literature for different molecular weights may not be representative of true molecular weight, but rather may be distorted by aggregation and solvation. In this report an effort to clarify this situation was conducted, first by using a suitable calibration with poly(ethylene glycol) and then using this polymer as a molecular size standard to determine the size of phenol–formaldehyde oligomers in solution. In the calculation of the molecular sizes of phenol–formaldehyde resols, proper accounting of the variation of the Mark–Houwink parameters with molecular weight for low degrees of polymerization must be made for poly(ethylene glycol). The Mark–Houwink constants for poly(ethylene glycol) are very similar in presence or absence of salts, and are considered to be unaffected by solution ionic strength. It is not the case for phenol–formaldehyde, whose apparent molecular size varies with the nature of the solvent. The actual molecular weight and molecular dimension distribution are discussed for different type A resols used as adhesives in the wood composite industry.