bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase separation in rubber‐modified thermoset resins: Optical microscopy and laser light scattering
Authors: Naé Hemi N. 
Published: April 2003

AbstractPhase Separation of a prereacted rubber in di‐, tri‐, and tetrafunctional epoxy systems is discussed. Optical microscopy and laser light scattering are used to characterize the morphology and dimensios of the rubbery domains. Systems without rubber are transparent while systems containing 2%, 4%, 6%, and 8% and rubber exhibit distinct phase separation. The average domain size is about 1 μm In the 8% systems the particles are larger and in the trifunctional system the rubbery domains are in the shape of shell and core. Laser light scattering proves that the scattering particles are in the core observed in the optical micrographs. The difference in morphologies is explained by the difference in the chemical structure of the epoxy resin and the rubber content. Thermodynamic considerations and solubility parameters show that the di‐ and tetrafunctional systems have similar enthalpies of mixing while the trifunctional system is much more incompatible with the rubber.
Shear modification of polyethylene
Authors: Ram Arie , Izrailov Lora 
Published: April 2003

AbstractPolymers like LDPE can be modified by applying a shearing process for an extended period. As a result the melt elasticity is reduced, as evidenced by the decrease in extrudate (die) swell at the exit of a capillary and onset of melt fracture. Melt viscosity was also slightly reduced; melt flow index (measured in short capillary) is highly increased. At the same time, melt density rises. All these parameters vary mostly for LDPE grades that exhibit the highest degree of long‐chain branching. It was confirmed that the intrinsic viscosisty of the polymer samples was essentially unaffected, so that chain scission may be ruled out. Moreover, the process itself is shown to be reversible as the initial parameters were recovered by special treatment, due to heating or solvation. The mechanism of shear modification is believed to consist of disentanglement of temporary couplings betwen long branches. The practical utilization of this process will be pursued, as well as the scientific understanding of structuring entangled branched chains.
Viscoelastic character of poly(ethylene oxide) in aqueous solutions: Effect of shear rate, concentration, salt, and anionic surfactant
Authors: Lance‐Gomez E. T. , Ward T. C. 
Published: April 2003

AbstractA technique useful for estimating the viscoelastic properties of dilute solution poly(ethylene oxide) was developed. With this technique, the effect of concentration, shear rate, presence of salt and/or anionic surfactant, and molecular weight on the viscoelastic properties in dilute solution were determined. Differences in the viscoelastic properties of commercial grade materials were observed. An explanation for the differences in salt and surfactant solutions based on formation of a weak ionic network is presented.
Mechanical properties of films of poly(vinyl alcohol) derived from vinyl trifluoroacetate
Authors: Yamaura Kazuo , Tada Masuo , Tanigami Tetsuya , Matsuzawa Shuji 
Published: April 2003

AbstractIn order to study the influence of the stereoreguralities of polymer chains on the mechanical properties of films of poly(vinyl alcohol) (PVA)(VTFA) derived from vinyl trifluoroacetate, the strength of the film was measured. In the case of undrawn PVA(VTFA) films, Young's modulus and strength at break were the smallest at the annealing temperature of about 100°C. It is considered to be due to the melt of small microcrystals and the increase in mobility of chains in amorphous parts. Young's moduli of undrawn PVA(VTFA) films were in the range of 1.50–3.75 GPs and the values were higher than that (0.17–0.36 GPa) of undrawn film of commercial PVA with the low concentration of syndiotacticity and the high concentration of head‐to‐head bounds. In the case of drawn, annealed PVA(VTFA) films, the maximum Young's modulus was about 20 GPa.
The density and composition of polyimide surface layers
Authors: Chauvin C. , Sacher E. , Yelon A. 
Published: April 2003

AbstractDensity measurements as a function of polyimide film thickness have revealed that the surface layers, each 1.5 μm in thickness, have a density lower than that of the bulk by a statistically significant 1%. Infrared measurements have confirmed that this is due to the presence of isoimide in these surface layers: because of its nonlinear nature, this impurity structure causes a decrease in the measured density.
Semi‐ and fully interpenetrating polymer networks based on polyurethane‐polyacrylate systems. IX. Properties of an isomerically related interpenetrating network
Authors: Hourston D. J. , Huson M. G. , McCluskey J. A. 
Published: April 2003

AbstractTwo polyurethane–poly(vinyl acetate) interpenetrating polymer networks of differing composition were synthesized and certain physical properties investigated. The results are compared with semi‐1‐interpenetrating polymer networks of the same system as well as with, where appropriate, polyurethane‐poly(methyl acrylate) interpenetrating polymer networks. Dynamic mechanical analysis clearly indicated phase separation for both compositions. The poly(vinyl acetate) glass transition showed a shift to lower temperatures accompanied by a shift to higher temperatures of the polyurethane transition. Such shifts indicate a certain extent of mixing. Electron microscopy confirmed phase separation and for a material with 20% by weight of polyurethane indicated that both components are continuous. This latter material also had a higher tensile strength and elongation at break than the corresponding poly(vinyl acetate) homopolymer. At 60% by weight of polyurethane the stress‐strain characteristics are those of a reinforced rubber. Certain modulus–composition theories, and, also, sonic velocity measurements were consistent with these morphological conclusions.
Thermal behavior of polyethyloxazoline
Authors: Keskkula H. , Paul D. R. 
Published: April 2003

AbstractPolyethyloxazoline (PEOx) is a new water‐soluble, thermoplastic polymer. It has a glass temperature of 56°C which increases to about 72°C on storage at room temperature. This increase is a manifestation of physical aging, and it occurs relatively fast with PEOx in comparison to other polymers. Also, the extent of this aging, as measured by the amount of enthalpy relaxation, is high for PEOx. It was shown that PEOx can be brought to 320°C without reduction of glass temperature, indicating an exceptional thermal stability.
Optimal periodic control of a continuous “living” anionic polymerization. I. Theoretical study
Authors: Frontini G. L. , Eliçabe G. E. , Couso D. A. , Meira G. R. 
Published: April 2003

AbstractWithin certain limitations, this work shows that the production of polymers with any prespecified number average chain length and polydispersity is theoretically feasible when “living” anionic polymerizations are carried out in continuous stirred tank reactors (CSTRs) which are under optimal periodic forcing of the feed flows. The optimal periodic control problem was solved adopting a suboptimal objective function and a novel iterative numerical procedure. When the objective function is minimized in order to reduce the time average polydispersity, then the operation tends to become a sequential semibatch process. Conversely, if the objective is to maximize these variables, then the reagent concentrations inside the reactor tend to be 180° out of phase. Different periods of oscillation must be selected depending on whether the required average polydispersities are above or below the steady state value of 2. The greatest flexibility in the MWD control is obtained with fast kinetics, and, in this case, average polydispersities between 1.06 and 9.2 may be required.
Studies on structural transformation of the sytrene‐grafted polyethylene film and fabric — grafting behavior and cavity formation mechanism
Authors: Hsiue Ging‐Ho , Huang Wen‐Kuei 
Published: April 2003

AbstractA new approach to prepare hydrophilic porous membranes is presented. Films and fabric made of polyethylene were grafted with styrene by simultaneous γ‐irradiation. The grafting behaviors of fabric are quite different from bulk films which exhibit the well‐known gel effect in styrene–methanol mixture solutions. The grafting rate for fabric increased monotonically with monomer concentration, and no maximum appeared on dilution with methanol. The copolymer films were further sulfonated to prepare hydrophilic membranes. Surface structure of membranes and fabrics were examined with optical and electron microscopy. For the fabric, the original smooth surface turned into rugged surface with different sizes of cavities. For membranes, the buldgelike bubbles are found when swollen with water. These bubbles changed into cavities after drying in vacuum at elevated temperature. The mechanism for the formation of such a structure is discussed. The electrical resistance of such membrane was low enough to be useful as battery separator.
Selective permeation of o‐, m‐, and p‐isomers of benzene derivatives through polymer membranes based on cyclodextrin complexation in the bulk aqueous solution
Authors: Anzai Jun‐Ichi , Kobayashi Yutaka , Ueno Akihiko , Osa Tetsuo 
Published: April 2003

AbstractTransport behavior of several aromatic compounds through a poly(vinyl chloride)membrane and poly(vinyl alcohol)‐poly(ethylenimine) composite membranes was studied in the presence of cyclodextrin in the aqueous solution. o‐Isomers of nitrophenol, nitroaniline, and iodophenol were effectively separated from their mixture of regio isomers based on the preferential complexation between cyclodextrin and the m‐ and p‐isomers over the o‐isomers. Pumping of p‐nitroaniline across the membrane was also observed by addition of cyclodextrin. The results were explained as a consequence of the selective complex formation between cyclodexarin and substrate and the low membrane permeability of the complexes.
Orientation behavior of ethylene diamine‐treated cottons with stress
Authors: Kalyanaraman A. R. 
Published: April 2003

AbstractThe decrystallization of natural cotton with Ethylene Diamine Treatment is well known. This paper analyzes the variation of X‐ray orientation with stress on ethylene diamine‐treated cotton fibers. For cotton fibers in the natural state, the elongation varies uniformly with the applied stress. It has also been pointed out by earlier work that the X‐ray orientation does not vary uniformly with increase in applied stress. With ethylene diamine treatment on natural cottons, the above trends are reversed and this is reported in the present investigation. This paper also indicates a possible explanation to support the above observation.
Studies in interaction between polyvinyl pyrrolidone and stilbene fluorescent compounds. Part I: Interaction with individual compounds
Authors: Sheth Geeta N. 
Published: April 2003

AbstractInteraction between polyvinyl pyrrolidone (PVP) and two stilbene‐type fluorescent compounds has been examined from the results of emission, excitation, and ultraviolet absorbance measurements. Results obtained indicate preferential interaction of the trans form of the fluorescent compound with PVP resulting in complex formation and increase in fluorescence due to such complex formation. However, at higher concentrations of PVP in the aqueous phase the cis form also forms a complex which has no fluorescing characteristics. The calculated values of free energy change indicate weak bonding between both the fluorescent compounds and PVP. Fluorescent compound‐binding capacity as well as the number of monomers of PVP combined remain more or less constant in the range of molecular weights of PVP studied.
Electron‐microscopical investigation of the morphology of segmented polyurethanes
Authors: Foks J. , Michler G. 
Published: April 2003

AbstractSegmented polyurethanes obtained by two‐step synthesis were studied by electron microscope on specimens prepared as replicas from the brittle surface of the polymer and on thin sections cut with a cryo‐ultramicrotome. Each of the specimens showed two different kinds of dispersed phase. Information obtained on morphology complemented each other. The continueous phase observed on the thin section directly by microscope showed no structure of its own and was similar in all polymers investigated, whereas the surface of the brittle fracture showed two kinds of continuous phase.
Dielectric properties of polymers containing dispersed TCNQ salts
Authors: Kita H. , Okamoto K. , Mukai S. 
Published: April 2003

AbstractTetracyanoquinodimethane salts have been incorporated into insulating polymers to raise their dielectric constants. Cast films prepared from mixtures of insulating polymers and tetracyanoquinodimethane salts in a solvent show a high dielectric constant (>20). The dielectric constant of the films varies with the tetracyanoquinodimethane salts. High values were attained with the films containing high‐conducting tetracyanoquinodimethane salts. These values remain constant over a range of frequencies (102–104 Hz). Dissipation factors and electric strength values of the films are also reported.
Effect of comonomer content and annealing on morphological changes in acrylic copolymers and fibers
Authors: Kulshreshtha A. K. , Garg V. N. , Sharma Y. N. , Dweltz N. E. 
Published: April 2003

AbstractA better understanding of internal microstructure is necessary to understand various properties of acrylic fibers, such as dyeability, mechanical properties, and comfort. In the present paper, the application of x‐ray methods for the investigation of fiber microstructural parameters, namely, crystallinity and crystallite size, is demonstrated. Effect of comonomer incorporation on acrylic copolymer microstructure is assessed in the present work. Influence of annealing aftertreatment on the changes in structure is investigated using the evidence presented by x‐ray and DSC studies. Introduction of small amounts of a comonomer (methyl acrylate, MA) results in diminishing crystallinity. Annealing of acrylic copolymers causes the onset of an intramolecular cyclization, as well as an increase in segmental mobility; both these factors lead to an increase in crystallinity and crystallite size. With increasing comonomer content, the exothermic peak in the thermogram is found to shift toward higher temperatures. Some evidence is presented that shows the effect of spinning process variables on acrylic fiber microstructure. The results and findings of the present work have been interpreted in terms of a two‐phase structure for acrylic fibers.
Permeation of N‐butane, propane and ethane through ethylcellulose
Authors: Casur Ertugrul , Smith Theodore G. 
Published: April 2003

AbstractThe permeation of n‐butane, propane, and ethane in ethylcellulose has been measured over a pressure range from 25 to 200 mm Hg and over the temperature range from 30 to 70°C. The permeation and diffusional time lag of each of the three gases in ethylcellulose is pressure dependent. Transport of the gases through ethylcellulose can be described by the partial immobilization model. It was found that, in general, the Langmuir‐mode species diffusion coefficients are lower than the Henry's law species diffusion coefficients. The logarithm of diffusion coefficients at zero penetrant concentration varies linearly with the square of the molecular diameter of n‐butane, propane, and ethane permeating through ethylcellulose. This relationship suggests that the diffusion process depends upon the availability of sufficient cross‐sectional area for the penetrant to diffuse. An Arrhenius temperature dependence was observed for permeation coefficients and diffusion coefficients for n‐butane, propane, and ethane in ethylcellulose. The activation energy of diffusion at zero penetrant concentration is directly proportional to the square of the gas molecular diameter and the entropy of activation. This observation is consistent with the view that the activation energy of diffusion is associated with the energy required to produce a space of sufficient cross‐section for the diffusion molecule to pass.
Percolation transition and conductivity in macroscopically anisotropic two‐component polymer membranes
Authors: Narȩbska Anna , Wódzski Romuald , Bukowski Zbigniew 
Published: April 2003

AbstractPercolation conductance has been studied for polypropylene/poly(acrylic acid) membranes (PP‐g‐PAA) prepared by volume grafting of an ionic component onto polypropylene foil. In these membranes the volume fraction of the conducting phase decreases from the surface to the center, brining some anisotropy into the composition. For this material, the “insulator‐ to‐conductor” transition proceeds at a critical volume fraction Vc equal to 0.395. It has been proved that this critical volume fraction and the critical exponent t, found to be below that predicted by theory, i.e., 1.2 ± 0.03 instead of 1.6 ± 0.2, result from the gradient in the distribution of the conducting component in the direction of the current flow. Computations of Vc and t for the same PP‐g‐PAA copolymer with a randomly distributed conducting component have led to Vc = 0.08 and t* = 1.53. A critical exponent t in that range is characteristic of three‐dimensional systems; however, Vc is rather low, suggesting a nonspherical shape for the conducting domains.
Cross‐linked polystyrene‐dithiocarbamate polymers: Use in heavy metal removal
Authors: Wagner Carol K. , Hall Gene , Riegel Bram , Virgilio John De , Kamath Vanita , Germann Geoffrey 
Published: April 2003

AbstractCross‐linked polystyrene polymers were converted to dithiocarbamate polymers. These polymers were used to remove heavy metal cations from water. Dithiocarbamate polymers can be understood to be inherently more stable toward hydrolysis than xanthate polymers.
Solution studies of metal sulfonate ionomers IV: Effects of cosolvents
Authors: Lundberg R. D. 
Published: April 2003

AbstractPrevious studies have shown that metal sulfonated ionomers display unusual solution behavior. Typically, inomers, such as metal sulfonated EPDM or sulfonated polystyrene, are readily dissolved in mixed solvents, such as hydrocarbons plus alcohols. Such mixed solvents can provide unusual viscosity‐temperature behavior due to the strong inter‐or intramolecular interactions of the ionic groups.This paper is concerned with studies directed at a variety of polar cosolvents, including amines, alcohols, acids, amides, and esters, in interactions with zinc sulfonated ethylene propylene diene monomer (sulfo‐EPDM). Within various classes of compounds the structural effects of such cosolvents on the solution viscosities of sulfonate ionomers have been elucidated. Generally, amines and alcohols have been found to be the most effective cosolvents. Amines appear to form a specific complex with zinc and can virtually eliminate ion pair association at extremely low levels. Within a homologous series, those compounds of shortest hydrocarbon chain length provide the most effective solvation of the ionic groups of sulfonated EPDM. The effect of structure of the amines or alcohols on solution viscosity has shown the efficiency of cosolvent interaction proceeding as normal > iso > secondary > tertiary in the alcohol series. These results are interpreted as a consequence of the cosolvent solvating the ionic groups wherein the more bulky cosolvents are least effective in solvating the metal cations.
Influencing the crystallization behavior of PET‐based segmented copoly(ether ester)
Authors: Zeilstra J. J. 
Published: April 2003

AbstractSegmented copoly(ether ester) based on poly(ethylene terephthalate) and poly(oxytetramethylene) suffers from having a rather low rate of crystallization. The crystallization behavior of this elastomer can be influenced by cocondensation of selected diols and addition of nucleating agents and plasticizers. Changes of the crystallinity and morphology are studied by differential scanning calorimetry and dynamic‐mechanical analysis, respectively. Mechanical properties in relation to the different crystallinites obtained are reported.
Grafting of 3‐chloro‐2‐hydroxypropyl acrylate onto chrome tanned collagen fibers
Authors: Klásek A. , Šimoníková J. , Kaszonyiová A. , Pavelka F. , Janda L. 
Published: April 2003

AbstractGrafting of 3‐chloro‐2‐hydroxypropyl acrylate onto chrome tanned collagen fibers, initiated by the redox system bisulfite/persulfate, has been investigated. Using the method of statistical planning of experiments regression equations have been obtained, describing the effect of monomer concentration and of initiation system constituents concentrations on monomer conversion, degree of grafting of collagen, and on physical properties of resulting composites. The relationship between the content of poly(3‐chloro‐2‐hydroxypropyl acrylate) in the composite and the swelling ability, water absorption, and tensile strength of the same is discussed. Moreover, results of morphology investigation of composites, prepared by grafting of various acrylic monomers onto collagen fibers, as obtained by electron microscopy, are presented and discussed.
Polymeric reaction of polymer‐monomer system irradiated by low energy electron beam. III. Adhesive property of pressure sensitive adhesive
Authors: Takiguchi Ryohei , Uryu Toshiyuki 
Published: April 2003

AbstractApplication of low‐energy electron beam to nonsolvent‐type pressure‐sensitive adhesive is investigated. Adhesive properties such as peel strength, dead load strength, and ball tack were closely related to the reaction behavior (gel fraction and graft efficiency) of the acrylate polymer‐monomer system. The reaction behavior is eluciadated by combining the measurements of gel fraction, infrared spectrum of gel, and molecular weight distribution detected by gel permeation chromatogrophy. It was found that the adhesive property of electro beamcured adhesives depends on the molecular weight of added polymer, monomer concentration, and irradiation dose. Graft polymerization and moderate crosslinking by electron beam irradiation especially contribute to superior high adhesive properties.
Aging of polypropylene using high oxygen pressure: Influence of sample thickness and stabilization
Authors: Faulkner Douglas L. 
Published: April 2003

AbstractThin films (0.05–0.08 mm thick) of stabilized and unstabilized polypropylene were aged under 4.24 MPa (614 psi) of oxygen at 90°C. The oxidation of these films was monitored using transmission infrared spectroscopy. Previously it was shown that embrittlement for the thin unstabilized polypropylene films occurred 3.6 times faster in 4.24 MPa of oxygen than in air at atmospheric pressure. For thick stabilized polypropylene (3.18 mm thick), the oxidative induction time at 120°C and 4.24 MPa of oxygen was drastically reduced compared with conventional air aging at this temperature. Specifically, sample embrittlement occured in 1 week during the high oxygen pressure aging in stark contrast to 70 weeks for conventional air aging. Consequently, due to the shortening of time to age samples at high oxygen pressures, aging can be conducted at this lower temperature (nearer the service temperature) rather than at this commonly used aging temperature of 150°C.