bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chemistry of Pd in cellulose acetate
Authors: Hwang Soon‐Taik , Shim Il‐Wun 
Published: April 2003

AbstractPd(OAc)2 complex has been incorporated in cellulose acetate (CA) as a dispersion medium using cosolvent (THF). The interactions Pd(II) complexes and cellulose acetate are examined by infrared spectroscopy and thermal analysis (DSC). The chemical reactivities of Pd–CA films have been investigated by reacting Pd sites with CO, H2, O2, and C2H4 in the temperature range 25–150°C and at the pressure of less than 1 atm. Two different Pd‐carbonyls and a Pd(O)‐hydride species formed in CA are characterized by their infrared spectra. Treatment of 10 wt % Pd–CA films with hydrogen (600 torr) at 70°C produces small Pd metal particles of ca. 30–60 Å in diameter in CA, which show catalytic activities under mild conditions in the reactions such as hydrogenation of C2H4 and oxidation of CO.
Percolation transition in heterogeneous ion exchange membranes
Authors: Šumberová V. , Bleha M. , Wodzki R. 
Published: April 2003

AbstractElectrical conductivity and permeability for NaCl and glucose of heterogeneous cation and anion exchange membranes was studied as a function of the type of ion exchanger and swelling water content. Using membrane composition and the character of data obtained, it was proved that the percolation theory is suitable for the interpretation of experimental results. It was found for both the cationic and anionic type of membranes that the “insulator to conductor” and “nonpermeable to permeable material” percolation transition proceeds at a critical water fraction approximately 0.25. The exponent τ of the scaling equation is approximately 1.6, thus lying in the vicinity of the theoretical value for three‐dimensional systems.
Secondary relaxation, brittle–ductile transition temperature, and chain structure
Authors: Wu Souheng 
Published: April 2003

AbstractWe show that the subglass secondary relaxation temperature at which a polymer changes from brittle (crazing) to ductile (yielding) behavior is a function of the characteristic ratio C∞ (which is a measure of the intrinsic flexibility and rigidity of a coiled chain). At 1 Hz frequency, the correlation is given by {Tβ}/{Tα} = Tb/Tg = 0.135 + 0.082C∞, where {Tβ} is the secondary relaxation temperature, which corresponds to Tb the brittle—ductile transition temperature, and {Tα} is the primary relaxation temperature, which corresponds to the glass transition temperature Tg at the given frequency. The ratio {Tβ}/{Tα} or Tb/Tg can be predicted from chemical structure alone.
Synthetic resins. XX. Chelation ion exchange properties of resins derived from semicarbazone of 2‐hydroxy acetophenone‐substituted benzoic acid–formaldehyde
Authors: Bastia T. K. , Lenka S. , Nayak P. L. 
Published: April 2003

AbstractA number of resins have been synthesized by reacting orthohydroxy acetophenone‐semicarbazone with substituted benzoic acid and formaldehyde in the presence of some acid and basic catalyst. The physicochemical properties of the resins have been reported. The ion exchange properties of the resins have been investigated. Influence of electrolytes on the metal uptake of Cu2+, Ni2+, Zn2+, Mg2+, and Mn2+ has been studied. The distribution of metal ions at different pH has also been reported. © 1992 John Wiley & Sons, Inc.
Measurement of the extent of reaction of an epoxy–cycloaliphatic amine system and influence of the extent of reaction on its dynamic and static mechanical properties
Authors: Jordan Catherine , Galy Jocelyne , Pascault Jean‐Pierre 
Published: April 2003

AbstractAn investigation was carried out into the effect of the extent of reaction on the mechanical properties, in a mixture of an epoxy prepolymer and a cycloaliphatic diamine, above the gel point. First, the most adequate technique to approach the extent of reaction was chosen between differential scanning calorimetry, Fourier transformation infrared, and size exclusion chromatography. It was found that the differential scanning calorimetry gave a good estimate of the extent of reaction, measuring the glass transition temperature and using a modified DiBenedetto equation. Dynamic mechanical properties and static mechanical properties are shown to be highly dependent upon the extent of reaction. The β relaxation was found to be responsible for the fracture properties at room temperature through the changes in extent of reaction. © 1992 John Wiley & Sons, Inc.
Removal of bacteria from water by systems based on insoluble polystyrene–polyethyelnimine
Authors: Tashiro Tatsuo 
Published: April 2003

AbstractA study was made of the removal of viable bacterial cells from sterilized physiological saline (saline) by insoluble polymer beads. The polymers (CMPS–PEI300 and CMPS–PEI600) were prepared by reactions of chloromethylated, divinylbenzene crosslinked polystyrene (CMPS) beads with polyethyleneimines (PEI) (MW = about 300 and 600). The bacterial strain cells used were Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa). Decrease coefficients (D, which corresponds to adsorption rate constant) for the viable cell numbers of E. coli by CPMS–PEI300 and CMPS–PEI600 were 28 and 120 (mL/gh) in saline, respectively. These D's were less than those (72 and 270 mL/gh) in sterilized, distilled, and deionized water (sterilized water). The D's for S. aureus and P. aeruginosa by CMPS–PEI600 were 46 and 76 (mL/g h), respectively. The D for E. coli by CMPS–PEI600 was compared with R (removal coefficient) for that by pyridinium type polymers. Bactericidal activity of PEI600 was examined on E. coli and P. aeruginosa in saline. Also, that of poly(ethylene glycol) 600 was done on E. coli in saline.
The adsorption of mercuric ions by chitosan
Authors: Peniche‐Covas C. , Alvarez L. W. , Argüelles‐Monal W. 
Published: April 2003

AbstractThe adsorption of mercuric ions by chitosan was investigated. The study of the adsorption kinetics shows that the rate of adsorption of mercuric ions on chitosan can be interpreted in terms of intraparticle diffusion as the rate‐limiting step. The experimental data of adsorption equilibrium from mercuric chloride solutions correlate well with the Langmuir isotherm equation, although at high‐solute concentrations, a multilayer type of adsorption with the subsequent increase in the uptake is observed. Column experiment confirms the ability of chitosan for the removal of mercuric ions from solutions in the absence of a high concentration of chlorides.
A new concentrated emulsion polymerization pathway
Authors: Ruckenstein E. , Sun F. 
Published: April 2003

AbstractTo ensure the stability of the concentrated emulsions that are employed as precursors for polymerization, a two‐step concentrated emulsion polymerization pathway is described. In the first step, the monomer is partially polymerized by heating at 50°C until a certain conversion is reached. Subsequently, the partially polymerized monomer is used as the dispersed phase to prepare a concentrated emulsion in which water constitutes the continuous phase. The concentrated emulsion has a large volume fraction of the dispersed phase (0.74–0.99) and the appearance of a gel. Several typical monomers are employed to correlate the stability of the concentrated emulsion and the extent of partial polymerization of the dispersed phase. It was found that monomers, which cannot lead to stable concentrated emulsions, can generate them after partial polymerization. Subsequent polymerization of the concentrated emulsion leads to latex particles. Copolymers and polymer composites were also prepared by the two‐step procedure. In the latter case, water was replaced with a solution of a hydrophilic monomer in water as the continuous phase. © 1992 John Wiley & Sons, Inc.
Thickness–direction thermal‐expansion measurements
Authors: Saraf Ravi F. , Tong Ho‐Ming , Poon Tze W. , Silverman B. David , Ho Paul S. , Rossi Angelo R. 
Published: April 2003

AbstractThermal expansivity in the thickness direction for three commercially synthesized and processed polyimide films, PMDA–ODA, BPDA–ODA, and BPDA–PDA, have been measured. The expansivity in the thickness direction is significantly higher than that in the in‐plane direction. The observed anisotropy is explained by the orientation texture of the films. The differences in the expansivity is explained by the molecular conformation of the chain. The latter is calculated by energy minimization excluding the entropic effects. The conformation analysis reveals a helical‐like conformation for ether‐linkage‐containing chains, which explains, which explains the higher expansivity in PMDA–ODA as opposed to BPDA–PDA. The possibility of helical conformation in PMDA–ODA and BPDA–ODA is novel. © 1992 John Wiley & Sons, Inc.
Effects of higher‐order structure of poly(3‐hydroxybutyrate) on its biodegradation. I. Effects of heat treatment on microbial degradation
Authors: Nishida Haruo , Tokiwa Yutaka 
Published: April 2003

AbstractTo clarify how the biodegradation of plastic is affected by physical properties based on the plastic's higher‐order structure, the microbial degradability of heat‐treated poly(3‐hydroxybutyrate) (PHB) samples was studied. Cast‐film samples and fibrous samples prepared with heat treatment were degraded by an isolated degrading bacterium: strain SC‐17. Consequently, it was found that the higher‐order structure properties such as crystallinity and modulus of elasticity of PHB acted as suppression factors. SEM observations of the degraded PHB films showed unique degradation patterns such as spherical and tubular holes on the surfaces and cells of SC‐17 in process of degrading the PHB surface. These patterns are thought to result from colonization of SC‐17 on the surfaces. From the results, it was suggested that the surface of the PHB was important as a growing field for the degrading bacterium and that the higher‐order structure properties of the PHB affected not only the degradation reaction but also the colonization of the degrading bacterium on the surface. © 1992 John Wiley & Sons, Inc.
Synthesis, characterization, and degradation of block polyesteramides containing poly(L‐lactide) segments
Authors: De Simone Vincenza , Maglio Giovanni , Palumbo Rosario , Scardi Vincenzo 
Published: April 2003

AbstractRandom multiblock polyesteramides (PEAs) having polyester (PE) content of 20–50 wt % have been prepared by low‐temperature polycondensation using sebacoyl chloride, 1,6‐diaminohexane, and telechelic oligomers of L‐lactide with Mn = 600–1500. The PEAs were characterized by IR and 1H‐NMR spectroscopy, wide‐angle X‐ray diffraction, and thermal analysis. Only the polyamide segments are able to crystallize, and the crystallinity depends on the composition and architecture of the PEAs. From viscosity and IR measurements it was established that the chain degradation of PEA powders or films suspended in buffer solutions occurs by hydrolysis of the ester linkages. The degradation rate is influenced by pH, PE content, and, to a lesser extent, by crystallinity. © 1992 John Wiley & Sons, Inc.
Structural changes of silk fibers induced by heat treatment
Authors: Tsukada Masuhiro , Freddi Giuliano , Nagura Masanobu , Ishikawa Hiroshi , Kasai Nobutami 
Published: April 2003

AbstractThe structural changes of silk fibers induced by heat treatment were investigated by thermomechanical analysis, dynamic mechanical measurements, X‐ray diffraction analysis, and refractive indices measurements. Bombyx mori silk fibers exhibited only a slight contraction, while tussah silk fibers showed a prominent two‐step contraction during the heating process. The dynamic storage modulus of B. mori fibers remained unchanged until the final decrease at about 170°C. The E' value of tussah fibers showed a slight increase ranging from 30 to 70°C and a final abrupt decrease at about 190°C. The broad peak of dynamic loss modulus showed a maximum at 220 and 230°C for B. mori and tussah silk fibers, respectively. The crystalline structure of silk fibers did not show any significant change regardless of heat treatment. The birefringence value of B. mori silk remained unchanged in the range from 25 to 240°C and then decreased, while that of tussah fibers decreased linearly. The isotropic refractive index increased for both silk fibers, even though with a different rate with increasing temperature. We proposed a schematic representation showing the structural changes of silk fibers induced by heat treatment, taking into account the changes in molecular orientation in the amorphous, laterally ordered and crystalline regions. © 1992 John Wiley & Sons, Inc.
Interactions of polymer model surfaces with cold plasmas: Hexatriacontane as a model molecule of high‐density polyethylene and octadecyl octadecanoate as a model of polyester. I. Degradation rate versus time and power
Authors: Clouet F. , Shi M. K. 
Published: April 2003

AbstractTo gain a better understanding of the evolution of polymer surfaces under cold plasmas, model polymer surfaces were studied. The degradation products and the gas phase were investigated by mass and optical emission spectrometry. Their evolution versus time and power enable us to propose a mechanism that involves atomic oxygen, OH* and H* radicals. © 1992 John Wiley & Sons, Inc.
Empirical prediction method of intrinsic light scattering loss of transparent amorphous polymers
Authors: Takezawa Yoshitaka , Taketani Noriaki , Tanno Seikichi , Ohara Shuichi 
Published: April 2003

AbstractWe studied simple empirical equations to estimate the values of intrinsic light scattering loss αR of various polymers applicable for plastic optical fibers, especially for aromatic amorphous polymers. The αR is divided into two losses, that is, αiso and αaniso. Here, αiso means the isotropic scattering loss; αaniso, the anisotropic scattering loss. The αiso is mainly a function of refractive index, and the αaniso is a function of refractive index, density, and the number of benzene rings in the polymer repeating unit. Therefore, when the polymer density and the structure of its repeating unit are known, the values of αR can be estimated. We derived new empirical equations for predicting the values of each intrinsic light scattering loss, αiso and αaniso. The estimated values were approximately equal to the experimental ones. The values of αR of aromatic amorphous polymers were not so large inherently, and they were a few hundred decibels per kilometer at the highest. © 1992 John Wiley & Sons, Inc.
Crosslinking reactions in pigmented olefinic polymers
Authors: Houde Carolyn , Schreiber H. P. , Rudin Alfred 
Published: April 2003

AbstractThermally initiated crosslinking reactions have been studied in a linear low‐density polyethylene, and an ethylene—propylene rubber. The polymers contained conventional thermal stabilizers or one of three surface‐coated rutile pigments. Enthalpies of crosslinking and reaction kinetics depended on the degree of terminal vinyl unsaturation in the polymers, that characteristic being greater in the rubber than in the polyethylene. The presence of thermal stabilizers did not exert any measurable influence on measured parameters of the crosslinking processes. The effects of rutile varied, depending on their surface acidity or basicity, as determined from chromatographic measurements. Basic rutile was found to reduce heats and to slow rates of reaction, while acidic rutiles did not affect the reactions. These observations may be attributed to interaction between the basic pigment surface and acidic moieties involved in the crosslinking reaction. © 1992 John Wiley & Sons, Inc.
Synthetic resins. XVIII. Chelation ion exchange properties of 2,4‐dinitrophenylhydrazone of 4‐hydroxy acetophenone–formaldehyde resins
Authors: Rath D. K. , Lenka S. , Nayak P. L. 
Published: April 2003

AbstractA large number of copolymers were synthesized by condensing 2,4‐dinitrophenyl hydrazone of 4‐hydroxy acetophenone (4HA 2,4 DNPH) with substituted benzoic acids/phenols and formaldehyde in the presence of NaOH or HCl as catalyst. The resins were characterized by IR spectra. The decomposition temperature, solubility parameter, and viscositv of the polymers have been determined. The ion‐exchange properties have been studied using the batch equilibrium method. The measurement of the distribution of a given metal ion between an aqueous solution and the resins has been performed. The investigation was carried out over a wide range of pH and varying the ionic strength of the medium. © 1992 John Wiley & Sons, Inc.
Correlation of properties with structure in ziegler polypropylenes
Authors: Ibhadon A. O. 
Published: April 2003

AbstractIsotactic polypropylenes, varying in molecular weight, crystallinity, and tacticity, were characterized by spectroscopic and chromatographic techniques in order to obtain suitable samples for investigating the effect of structure on properties. Mechanical and thermal properties were studied with respect to their structural dependence. Melting points and rates of crystallization were observed to be higher in the more stereoregular samples, while evidence of fractionation by molecular weight and tacticity was observed in less stereoregular samples. Tensile properties displayed marked dependence on polymer stereoregularity, while examination of fractured surfaces by microscopy showed that fracture occurred at regions of high impurity concentration. © 1992 John Wiley & Sons, Inc.
Kinetic study of the polycondensation of diisocyanates with polyols
Authors: Krol P. , Atamanczuk B. , Pielichowski Jan 
Published: April 2003

AbstractOn the basis of kinetic studies of noncatalyzed synthesis of carbamates in chlorobenzene solution, a kinetic model of polyurethane synthesis has been proposed. The model was built on a set of elementary, sequential—parallel reactions between functional groups of the main reagents involved in polyurethane synthesis. The assumption that reactivity of reagents did not depend of their mol wt allowed simulation of the kinetics of formation of allophanate branches for various process parameters. It has been found that the process temperature and initial ratio of reagents are of primary importance. A set of equations, describing the synthesis of linear polyurethanes, has been derived. The equations afford calculation of the degree of polymer chain branching and their application yields results similar to those obtained by the more general method based on numerical solution of the differential equations involved. Advantages resulting from the mathematical modeling of the process kinetics have been pointed out. © 1992 John Wiley & Sons, Inc.
Application of NMR spectroscopy to the characterization of elastomer/filler interactions
Authors: Legrand A. P. , Lecomte N. , Vidal A. , Haidar B. , Papirer E. 
Published: April 2003

AbstractProton spin–spin relaxation time measurements have been performed at 300 and 400 MHz on bound rubber‐filler mixes resulting from the solvent extraction of silica‐filled and silicafilled‐modified polybutadiene, on the one hand, and of carbon black‐filled and carbon blackfilled‐modified styrene butadiene rubber, on the other hand. Two relaxation times are observed for all samples. They are ascribed to the occurrence of tightly and loosely bound rubber components, respectively. The effect of the grafting modification of the fillers on the formation of bound rubber and its two components is discussed. © 1992 John Wiley & Sons, Inc.
Gas sorption in poly(butylene terephthalate). II. Influence of crystallinity and molecular orientation
Authors: Zhou Z. , Schultze J. D. , Springer J. 
Published: April 2003

AbstractSorption measurements of CO2, Ne, and Ar in poly(butylene terephthalate) (PBTP) films were studied by the gravimetric method with a recording microbalance at 298 K in the pressure range of 1–22 bar. The semicrystalline samples were annealed and oriented at 373 K. The sorption isotherms for CO2 in PBTP films in the glassy state can be well described by the dual‐sorption theory. The nonlinear sorption behavior of Ne and Ar can be satisfactorily analyzed using the sorption model developed for noble gases in PBTP. For the undrawn annealed films, it has been found that the increment of crystallinity leads to the reduction of the equilibrium gas concentration. For the oriented films, the gas concentration rises with increasing draw ratio. It appears that the sorption behavior for all tested gases in the oriented PBTP films does not depend on the changes of crystallinity and crystalline morphology under extension. The difference of the critical pressure p* indicates the change in the size of the frozen microvoids existing in the noncrystalline phase, which was altered by annealing and drawing. © 1993 John Wiley & Sons, Inc.
Studies of the preparation, structure, and properties of an acrylic chelating fiber containing amidoxime groups
Authors: Lin Weiping , Lu Yun , Zeng Hanmin 
Published: April 2003

AbstractPolyacrylonitrile fiber was treated with hydroxylamine to form a chelating fiber containing the amidoxime group with high adsorption capacity to the Au3+ ion (up to 626 mg/g, when the nitrile group conversion reaches 53.7%), reasonable mechanical properties, and good thermal stability; the relationship among reaction conditions, fiber structures, and properties were investigated. The amidoxime group content rapidly increases to a steady value with increasing reaction time or HONH2 • HCl concentration, the fiber strength drops linearly with increasing reaction time, when the reaction takes place at the temperature where the morphology and order structure begins to be destroyed, and the amidoxime group content increases significantly, while fiber strength decreases remarkably. It is suggested that, to prepare a chelating fiber with high adsorption capacity and reasonable mechanical property, the reaction could be carried out at temperatures from 70 to 75°C, time of about 30 min, and concentration around 75 g/L. © 1993 John Wiley & Sons, Inc.
Estimation of free volume in poly(trimethylsilyl propyne) by positron annihilation and electrochromism methods
Authors: Yampol'skii Yu. P. , Shantorovich V. P. , Chernyakovskii F. P. , Kornilov A. I. , Plate N. A. 
Published: April 2003

AbstractThe free volume of poly(trimethylsilyl propyne) (PTMSP), a glassy polymer distinguished by extremely high gas permeability and diffusion coefficients, was determined by means of two probe techniques—the positron annihilation method and the electrochromism method. Lifetime analysis of positron annihilation spectra revealed an additional long‐lived component that is not typical for most of previously studied polymers. A model that has been developed earlier predicts that this lifetime corresponds to the larger size of free‐volume elements having an intrinsic radius of about 6 Å. Therefore, PTMSP should be similar to porous inorganic sorbents. A comparison with the literary data for zeolites and silica gel confirms this. According to the electrochromism method, the temperature dependence of the size of free‐volume elements for PTMSP is much weaker than that for regular glassy polymers like polystyrene. It was concluded that the great free volume in glassy PTMSP is associated with very loose packing of the chains. © 1993 John Wiley & Sons, Inc.
Reaction injection molding (RIM) system based on metathesis
Authors: Asrar Jawed 
Published: April 2003

AbstractThis paper describes the polymerization and the copolymerization of dicyclopentadiene and norbornene nitrile by metathesis polymerization. It is found that the metathesis polymerization of dicyclopentadiene, which is very fast and exothermic, can be controlled by the addition of norbornene nitrile. Though the norbornene nitrile delays the polymerization at room temperature, at high temperatures, because of the presence of nitrile group, polymerization is accomplished in reaction injection molding time. Physical and mechanical properties of the polymers and copolymers are described. © 1993 John Wiley & Sons, Inc.