bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the thermal histories on case II sorption kinetics: Test of a kinetic theory for swelling
Authors: Sarti G. C. , Apicella A. , De Notaristefani C. 
Published: April 2003

AbstractCase II sorption kinetics have been analyzed for PS–n‐hexane systems. Samples of polystyrene characterized by several different annealing histories were used. For all thermal histories, the n‐hexane sorption kinetics at several temperatures were measured, as well as some relevant mechanical properties of the glassy matrix, e.g., density and initial stress for crazing. The main influence of the thermal history is to appreciably alter the initial stress for crazing σc, as well as the swelling kinetics. The σc curve vs. annealing time is seen to go through a minimum which is paralleled, at 40°C, by a maximum in the swelling kinetics. The independent mechanical and sorption data obtained were compared with a recently proposed [G. C. Sarti, Polymer, 20, 827 (1979); G. C. Sarti and A. Apicella, Polymer, 21, 1031 (1980)] theory for Case II kinetics, which is shown to be particularly suitable to describe the observed behavior.
Mercerization of cellulose. I. X‐ray diffraction evidence for intermediate structures
Authors: Okano T. , Sarko A. 
Published: April 2003

AbstractA study of the mercerization of ramie cellulose was begun using x‐ray diffraction, in order to determine the types of alkali–cellulose structures that occur as intermediates during the conversion of cellulose I to cellulose II. A total of five unique alkali–celluloses (Na–celluloses) could be generated reproducibly, depending only on the alkali concentration used. The reproducibility was enhanced by slowing down the mercerization process, by laterally compressing the fibers in capillary tubes. The five structures, named Na–celluloses I, IIA, IIB, III, and IV, were of two types based on their crystallographic fiber repeats. The first type was represented by Na–celluloses I, III, and IV, all exhibiting a ca. 10 Å repeat. The second type was represented by Na–celluloses IIA and IIB, with a ca. 15 Å repeat. The latter structures are possibly based on a threefold helical chain conformation, which has not been seen in crystalline celluloses. All Na–cellulose structures exhibited a reasonable degree of crystallinity and high degree of fibrous orientation. They formed a definite interconversion scheme, marked by crystalline‐to‐crystalline phase transformations.
Kinetics of phthalic anhydride/ethylene carbonate reactions
Authors: Fagerburg D. R. 
Published: April 2003

AbstractThe kinetics of the polymerization of phthalic anhydride with ethylene carbonate to give poly(ethylene phthalate) were studied to elucidate the reaction mechanism. Zero‐order kinetics were observed to varying degrees of reaction depending upon reaction temperature. Although no clear‐cut overall reaction order could be established, previously proposed mechanisms involving decomposition of the carbonate as the first step of the reaction were ruled out. The chain propagation step was on the order of or faster than the initiation step of the reaction. Virtually no ether–glycol species were formed during the polymerization. A new mechanism was proposed for the polymerization.
Study of mechanical properties of urethane‐chlorinated rubber graft copolymer system. I
Authors: Anbazhagan K. , Reddy C. Rami , Joseph K. Thomas 
Published: April 2003

AbstractThe isocyanate‐terminated urethane prepolymer was prepared from toluene diisocyanate and a mixture of castor oil‐polypropylene glycol (PPG) (MW 2000). The chlorinated rubber (CR) graft copolymers (A and B) containing small percentage of hydroxyl groups were mixed with the urethane prepolymer in different proportions (1:1, 2:3, and 1:2), and the films were cast using these systems. Tensile strength and percent elongation were evaluated for A and B series with and without triethanolamine (TEA). Morphological characteristics of the films were also studied by using a scanning electron microscope (SEM). Deviations noticed in tensile strength values at yield as well as at break for A and B series and for the samples cured with additional TEA have been discussed.
Thioether glycidyl resins. V. Products of condensation of 1,4‐, 1,5‐di(mercapto)naphthalene and 4,4'‐di(mercapto)diphenyl with epichlorohydrin
Authors: Charmas Władysław 
Published: April 2003

AbstractThioether glycidyl resins produced by condensation of isomeric 1,4‐, 1,5‐di(mercapto)naphthalenes and of 4,4'‐di(mercapto)diphenyl with epichlorohydrin were obtained by heterophase alkaline condensation in water and isopropyl alcohol solution by sodium hydroxide solution. Their structure was determined by elemental analysis and IR and NMR spectra. The physical and chemical properties were determined. Some properties of the resins were determined during thermal and chemical curing with the curatives typical for epoxy resins. The cured compounds were characterized from derivatographic, thermomechanical, and mechanical studies.
Metals as synergistic fire retardants in polyethylene–silicone blends
Authors: Maclaury M. R. , Schroll A. L. 
Published: April 2003

AbstractThe role of lead compounds in blends of polyethylene and silicone has been studied as a flame retardant. It has been established that these compounds work in the solid phase and that a gas‐forming reaction is important to produce a foamed char which retards further combustion.
Surfactant titration technique: An improved approach for determining latex adsorption isotherm endpoints
Authors: Maurice Alvin M. 
Published: April 2003

AbstractA unique approach has been developed for determining surfactant titration end points via computer analysis utilizing nonlinear regression. This approach fits the data to an equation and then mathematically solves this equation to yield a reproducible endpoint. In this study, this computer program was utilized to interpret titration data for model acrylate, methacrylate, and styrene homopolymer and copolymer systems.
Characterization of Na ion‐sensitive solvent polymeric membranes based on a neutral carrier
Authors: Maruizumi Takuya , Miyagi Hiroyuki , Takata Yoshinori , Kobayashi Teruaki 
Published: April 2003

AbstractThe states in the surface and the bulk phases of Na ion‐sensitive polymeric membranes based on a synthetic carrier were investigated using SEM, IR, 13C‐NMR, and GC. The 13C‐NMR study revealed that conformation change of the carrier took place when the carrier was incorporated into the membrane phase. From SEM, IR, and 13C‐NMR experiments with a deteriorated membrane, the conformation change of the carrier was proposed as one of the deterioration factors other than the decrease in the diffusion coefficient of the carrier in the membrane phase.
Polymerization of p‐cresyl glycidyl ether catalyzed by imidazoles I. The influence of the imidazole concentration, the reaction temperature, and the presence of isopropanol on the polymerization
Authors: Berger Joseph , Lohse Friedrich 
Published: April 2003

AbstractThe polymerization of p‐cresyl glycidyl ether catalyzed by imidazoles has been investigated as a model reaction for the polymerization of technical epoxy resins. The dependence of oligomer yield on time, temperature, and imidazole concentration, the distribution of the polymerization degrees, and the influence of isopropanol have been studied. The reaction rate and the average degree of polymerization are affected by the presence or absence of a secondary nitrogen on the imidazole, i.e., different results are obtained when 2‐ethyl, 4‐methyl imidazole (EMI) or 1‐methyl imidazole (1‐MIA) are used. 1‐MIA seems to be “precursor” of the catalyst rather than a catalyst by itself. The comparisons of CGE polymerizations catalyzed by 1‐MIA in the absence and presence of isopropanol show only quantitative differences: The polymerization in the presence of isopropanol is faster, and the average degree of polymerization is shifted to higher values. The activation energies of CGE polymerizations catalyzed by different imidazoles have been determined.
Forced oscillations in continuous flow stirred tank reactors with nonlinear step growth polymerization
Authors: Gupta Santosh K. , Nath Sunil , Kumar Anil 
Published: April 2003

AbstractThe self‐step growth polymerization of RAf monomers in homogeneous, continuous flow stirred tank reactors (HCSTRs) is simulated under conditions of periodic feed concentration (with frequency ω and amplitude α). By having periodic operation, the polydispersity index of the polymer is found to increase by about 35% over the values at steady state. Periodic operation of HCSTRs is found to lead to gelation only for certain values of the frequency and the dimensionless residence time τ*. Gelling envelopes have been obtained to give conditions under which HCSTRs should be operated. These envelopes can be described in terms of two critical dimensionless residence times, τ and τ such that nongelling operation is always ensured when τ* < τ. For τ* > τ, periodic operation always leads to gelation, and HCSTRs cannot be used. For τ < τ* < τ, the gelling behavior is found to depend on the functionality f, amplitude α, and the dimensionless residence time τ*.
Use of sterically stabilized polymer colloids as electrostatically‐based liquid developers
Authors: Croucher M. D. , Lok K. P. , Wong R. W. , Drappel S. , Duff J. M. , Pundsack A. L. , Hair M. L. 
Published: April 2003

AbstractLiquid immersion development (LID) of a latent electrostatic image has become established as an important alternative to dry toning during the past decade. In this development method, a charged, colloidally stable colored particle that is dispersed in a dielectric fluid undergoes electrophoresis under the influence of an applied field. These particles then neutralize a latent electrostatic image of opposite polarity, which resides on either a photoreceptor drum or on dielectric paper. This results in a hard copy of the latent image being obtained. In this paper we outline the physicochemical properties that are demanded of a liquid toner and describe an alternative approach to the preparation of a LID materials package. This new approach utilizes a nonaqueous polymer colloid as the vehicle, which when colored and charged, gives a LID toner. The advantage of nonaqueous dispersions is that the steric stabilizer is irreversibly attached to the particle. Since desorption of the stabilizer is not a problem, these materials are colloidally stable for an indefinite period of time. The particles were colored using both dyes and pigments. While neither approach was entirely satisfactory, the feasibility of coloring such particles was demonstrated. A positive charge was imparted to the particles by specific adsorption of the cation of a metal soap at the polymer–fluid interface. It was found that these experimental LID toners were able to develop a latent electrostatic image in a commercially available printer with the image being well fixed to the paper. While this approach has not been optimized, it appears to be an attractive route for preparing novel LID developers.
Properties of UV‐curable polyurethane acrylates: Effect of reactive diluent
Authors: Speckhard T. A. , Hwang K. K. S. , Lin S. B. , Tsay S. Y. , Koshiba M. , Ding Y. S. , Cooper S. L. 
Published: April 2003

AbstractSeveral families of UV‐cured polyurethane acrylates were synthesized, and the effects of reactive diluent type and content on their physical properties were investigated. Increasing reactive diluent content promoted the development of a second, high glass transition temperature phase in all the materials, thereby leading to increased strength and modulus. Changes in the extensibility of the samples upon addition of reactive diluent were inversely related to the effect of the diluent on the crosslink density. The effects of using different reactive diluents (di‐, tri‐, and tetraethylene glycol diacrylate and N‐vinyl pyrrolidone) on the physical properties of the samples were attributed to differences in the softening point (Tg) of the homopolymer reactive diluents and the relative compatibility of the reactive diluents with the urethane acrylate segments.
Photopolymer morphology: Phase separation during polymerization
Authors: Maerov S. B. 
Published: April 2003

AbstractMorphology and phase structure were studied before and after photopolymerization for the binder–monomer system: poly(styrene/sec‐butylmaleate)(50/50)–trimethylolpropane triacrylate (TMPTA)(75/25). Films supported on a suitable substrate were measured by dynamic mechanical analysis and by dielectric relaxation before and during photocrosslinking. Such film support techniques also allow a variety of physical and chemical treatments to be carried out to determine structure changes. Two phases and a secondary transition were identified. The shift in temperature of both Tg's during photopolymerization and concurrent, fracture‐surface electron photomicrography were consistent with a mechanism involving phase separation of TMPTA during polymerization. Probable composition of the phases is discussed.
Sorption and permeation of iodine in water‐swollen poly(vinyl alcohol) membranes and iodine complex formation
Authors: Kojima Yoshitsugu , Furuhata Ken‐Ichi , Miyasaka Keizo 
Published: April 2003

AbstractThe sorption and the permeation of iodine in water‐swollen poly(vinyl alcohol) (PVA) membranes and the formation of PVA–iodine complexes were studied. The logarithms of the permeability and the diffusion coefficient decreased approximately linearly with the increase in polymer volume fraction. When the membrane was soaked in an aqueous I2–KI solution, it contracted and Young's modulus increased. These findings were explained in terms of the formation of extra junction points due to the PVA–iodine complexes. These changes were reversible and could be recovered by replacing the solution with water. The length of the polyiodine chain increased with the increase in the degree of hydration of the membrane. At a fixed degree of hydration, Young's modulus of an iodine‐sorbed membrane was much greater than that of a membrane soaked in pure water. This finding was explained on the basis of a double‐network structure. The extension of the membrane promoted the complex formation, and the complex disappeared when the tension was released. The critical strain necessary for the complex formation was independent of the degree of hydration. The length of polyiodine chain increased with strain and became constant at higher strains.
Adiabatic photopolymerization of acrylamide
Authors: Rodriguez Ferdinand , Chu Connie H. , Chu W. T. Wayne K. , Rondinella Mary Ann 
Published: April 2003

AbstractAlthough the adiabatic polymerization of acrylamide using photoinitiation was first described over 30 years ago, it still offers convenient opportunities for innovation. In the present work, the effect of EDTA (ethylenediaminetetraacetic acid, tetrasodium salt) as a reducing agent with two photosensitizers is described. With riboflavin‐5'‐phosphate sodium, the rate of polymerization rises with the ⅓ power of the EDTA concentration. With a new photosensitizer, 4‐benzoyl‐N,N,N‐trimethylbenzenemethanaminium chloride, the rate rises with the ½ power of the EDTA concentration. Adiabatic temperature rise is used as the measure of conversion in the early stages of polymerization.
A scheme to predict the morphology of diblock copolymers and their blends
Authors: Hsiue Ging‐Ho , Shih Solomon Weng Feng 
Published: April 2003

AbstractDiblock copolymers of α‐methylstyrene and isoprene were synthesized anionically. The morphology of the copolymers and of their blends with the homopolymers was studied by transmission electron microscopy. Based on this, a scheme is proposed to predict the morphological behavior associated with the blending of block copolymers with homopolymers. Two blending systems are discussed. They are (i) copolymer AB with homopolymers A and B and (ii) copolymers AB of two different molecular weights with homopolymer A. Two factors are considered to be the most crucial. One is the morphology of the predominant polymer (50 wt %), and the other is the weight ratio of the blends. The solubilizing effect of the block copolymer AB in the blend must also be taken into account. When the two copolymers are blended, the one with lower molecular weight was emulsified by higher one and restricted around the longer chain. It is shown that the present scheme is successful in predicting the morphology of diblock copolymers and their blends.
Effect of catalysts on the reaction between a cycloaliphatic diisocyanate (H‐MDI) and n‐butanol
Authors: Yilgör Ískender , McGrath James E. 
Published: April 2003

AbstractKinetics of the reaction between bis(4‐isocyanatocyclohexyl)methane, H‐MDI, and n‐butanol was studied in toluene at 100°C. Effects of various catalysts, such as Hg(CH3COO)2, Zn(CH3COO)2 · 2H2O, SnCl4 · 5H2O, and dibutyltindilaurate on the reaction rate and kinetics were also investigated. Reactions were followed by determining the unreacted isocyanate as a function of reaction time, using the standard dibutylamine back titration method. All catalysts seem to be very effective in increasing of the rate of the reaction compared to the uncatalyzed system. Depending on the initial stoichiometric ratio of (NCO) and (OH) and the concentration of the catalyst used, it seems possible to have preferential catalysis of the primary reaction between (NCO) and (OH) over the side reactions.
The effects of 3‐MeV proton radiation on an aromatic polysulfone
Authors: Coulter Daniel R. , Smith Mark V. , Tsay Fun‐Dow , Gupta Amitava , Fornes R. E. 
Published: April 2003

Abstract3‐MeV proton beam irradiation studies have been carried out on a commercial aromatic polysulfone (Udell 1700). Physical and mechanical property changes have been monitored as a function of dose. Chemical and spectroscopic analyses have also been performed on the irradiated samples. Results have been compared to those from previous studies with electrons and γ‐radiation. A mechanism of proton‐induced degradation is proposed.
Block copolymers of n‐propyl p‐styrene sulfonate with isoprene and styrene: Synthesis, characterization, and phase separation behavior
Authors: Whicher S. J. , Brash J. L. 
Published: April 2003

AbstractA series of ABA block copolymers based on n‐propyl p‐styrene sulfonate (A block) and isoprene or styrene (B block) were synthesized and characterized. The synthesis was based on methods developed previously for the anionic polymerization of n‐propyl p‐styrene sulfonate [S. J. Whicher and J. L. Brash, J. Polym. Sci., Polym. Chem. Ed., 19, 1995 (1981)], and consisted of forming a polyisopryl dianion by initiation with sodium naphthalene in THF at 0°C. n‐Propyl p‐styrene sulfonate was then added and propagated at −94°C. As was the case for n‐propyl p‐styrene sulfonate alone, it was found that only limited chain growth of this monomer initiated by living polyisoprene was possible, resulting in maximum A block molecular weights of about 10,000. The phase separation behavior of copolymers having a range of composition, as well as that of a blend of polyisoprene and poly(n‐propyl p‐styrene sulfonate) was investigated by examining thin films in the electron microscope. In the copolymers, phase separation was observed with transmission EM when THF was used as the solvent for film casting. Domain morphology was as expected for the various copolymer compositions. When films were cast from chloroform, phase separation was minimal, although it could be improved by annealing. Annealing produced relatively diffuse intermixed domains which occasionally formed unusual triangular patterns. Phase separation of the blend of homopolymers gave domains that were large enough to be mapped with SEM using both secondary electron and EDXA detectors.
Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide
Authors: Hebeish A. , Abdel‐Gawad Ib. Ib. , Basily Is. K. , El‐Bazza S. 
Published: April 2003

AbstractThe action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.
Structural characteristics, rheological properties, extrusion, and melt spinning of 60/40 poly(hydroxybenzoic acid‐coethylene terephthalate) (PHB/PET)
Authors: Sugiyama Hiroshige , Lewis David N. , White James L. , Fellers John F. 
Published: April 2003

AbstractThe rheological properties, extrusion, and melt spinning characteristics, and concomitant morphological features of 60/40 PHB/PET aromatic copolyester have been investigated. The material flows at temperatures above 190°C, but all crystallites may not melt completely until about 250°C. The material exhibits a yield stress value in shear flow. In fact, yield stress values were measured over a range of temperature from 190 to 260°C and estimated at higher temperatures. Extrudate swell measurements were also made in the same range. Significant extrudate swell does not occur until the fluid is at a temperature where the yield stress is approximately 1/50th of its maximum value. Extrudates are fibrillar in character and exhibit significant levels of crystalline orientation. The level of crystalline orientation in melt spun fibers does not vary significantly with drawdown ratio, since it is apparently developed to near its limiting extent during its flow through the die. All of these responses are similar to those observed in melt flow/processing studies of thermotropic liquid crystalline hydroxypropylcellulose.
Processing–morphology–property relationships in epoxy resins
Authors: Mijović Jovan , Williams John G. , Donnellan Tom 
Published: April 2003

AbstractAn investigation was conducted into processing–morphology–property relationships of a series of epoxy resin formulations. Diglycidyl ether of bisphenol A (DGEBA) epoxy resin was cured with diethylene triamine (DETA) and 2,5‐dimethyl 2,5‐hexane diamine (DMHDA). The two systems were compared by electron microscopic investigation and thermomechanical and fracture property measurements. Transmission electron microscopy has revealed a difference in the morphology of fracture surfaces. On the other hand, thermomechanical and fracture properties of DETA‐ and DMHDA‐cured formulations were found to be very similar. Three different processing (curing) conditions were used for DMHDA‐cured formulations, without an apparent effect on their properties. The previously reported improvement in impact energy of DMHDA‐cured formulations is unfounded.