bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure–property relationship in heat‐set poly(ethylene terephthalate) fibers. IV. Recovery behavior
Authors: Gupta V. B. , Ramesh C. , Gupta A. K. 
Published: April 2003

AbstractThis study describes the recovery behavior from tensile strains of up to 0.15, of oriented poly(ethylene terephthalate) (PET) fibers, which were heat‐set at different temperatures while free to relax and when held taut at constant length at room temperature. The taut annealed samples showed superior recovery behavior over the strain range studied. From structural studies on these samples, and also from FTIR studies of structural changes during deformation on similar shapes, it is concluded that, while the recovery behavior in the free‐annealed samples is dominated by the amporphous phase, both the crystalline and the amorphous phases influence the recovery behavior of the taut‐annealed samples.
Surface studies of polystyrene–poly(methyl methacrylate) diblock copolymers precipitated by different precipitants
Authors: Sohn Jeongin , Ree Taikyue 
Published: April 2003

AbstractDiblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with varying compositions in the mole fractions of PS were prepared, and were obtained in particle state by different methods of precipitation. The morphology of the precipitates was studied by electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and viscometry. From these studies it was found that the precipitates of diblock copolymers have core‐micelle structures, the components of the core and the surrounding micelle being different by precipitation histories.
Bimodal crystalline orientation in polypropylene: Mechanism of formation
Authors: Sakthivel A. , Abhiraman A. S. 
Published: April 2003

AbstractMelt‐spun polypropylene fibers have two sets of crystallites, each with a different preferred orientation. A probable kinetic mechanism of nucleation and growth of the two sets of crystallites, based on an analysis of crystallization in oriented polymers, is proposed. Experimental data on the fractions of these two sets of crystallites in as‐spun fibers and the effect of subsequent drawing or thermal annealing on the relative amounts of these two sets are presented.
Thioetherglycidyl resins. IV. Products of condensation of isomeric di(mercaptomethyl)xylene with epichlorohydrin
Authors: Charmas Władysław , Podkościelny Wawrzyniec 
Published: April 2003

AbstractThioetherglycidyl resins produced by condensation of isomeric di(mercaptomethyl)xylene with epichlorohydrin were obtained by heterophase alkaline condensation in water and isopropyl alcohol solution using sodium hydroxide. The structure of thioetherglycidyl resins was determined by elemental analysis, infrared, and NMR spectra, and their physical and chemical properties were defined. Some properties of the resins, cured chemically or thermally with typical for epoxy resins, and thermal and mechanical properties of the cured compounds were determined.
Polymer surface reconstruction by diffusion of organic functional groups from and to the surface
Authors: Gagnon David R. , McCarthy Thomas J. 
Published: April 2003

AbstractThree nonpolar organic polymers containing small amounts of polar functionality were studied with regard to their surface characteristics. Two of the materials, potassium chlorate/sulfuric acid‐oxidized polyethylene and poly(ethylene‐co‐acrylic acid) display variable surface polarities which can be reversibly accessed by heating films of the polymers in air or aqueous sodium hydroxide. Sodium‐reduced Teflon–FEP did not exhibit this characteristic. A combination of contact angle, ESCA, and ATR IR data are used to display that the surface changes are caused by migration of functional groups within the outer few tens of angstroms of the surface.
Optical characterization of solid‐state coextruded PET
Authors: Sun T. , Kyu T. , Sheng J. , Lefebvre D. , Stein R. S. , Porter Roger S. 
Published: April 2003

AbstractAmorphous poly(ethylene terephthalate) has been solid state coextruded to a series of draw ratios up to 4.4 at 50, 60, 70 and 90°C. These uniaxially drawn samples have been examined by optical microscopy and light scattering and for increases in crystallinity and birefringence as a function of draw ratio and draw temperature. The birefringence for PET may be among the highest yet reported—0.21.
Thermally induced phase separation in homogeneous blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) with poly(o‐fluorostyrene‐co‐p‐chlorostyrene) and with poly(o‐fluorostyrene‐co‐o‐chlorostyrene)
Authors: Vuković R. , Kureǎević V. , Karasz F. E. , Macknight W. J. 
Published: April 2003

AbstractThe phase separation behavior of initially compatible blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) with poly(o‐fluorostyrene‐co‐p‐chlorostyrene) [poly(oFS‐co‐pCIS)] and with poly(o‐fluorostyrene‐co‐o‐chlorostyrene) [poly(oFS‐co‐oCIS)] was studied by DSC. It was found that copolymers of poly(oFS‐co‐pCIS) containing between 15 and 62 mol % pCIS have shown no phase separation after annealing at temperatures up to 320°C. It was also observed that blends containing this copolymer with 74 mol % pCIS show phase separation at 250°C, which depended on blend composition. Additionally, all PPO/poly(oFS‐co‐oCIS) blends exhibit phase separation after annealing to a temperature of 230°C. Thermal degradation of the polymer blends was not observed at the temperatures studied.
Characterization of cis‐1,4‐polyisoprene polymerized with lanthanide catalyst system (Ln‐PIR)
Authors: Baogong (Chien, Pao‐Kung) Qian , Fuseng Yu , Rongshi Cheng , Wanjun Ruan Meina Zhang , Shentian Li , Yanshou Zhang , Yuhua Yang 
Published: April 2003

AbstractThe PIR raw rubber samples, Ln–PIR and Ti–PIR, were subjected to molecular characterization, which shows that Ln–PIR contains microgel particles, but the least branching in its macromolecular chains; its cis‐1,4 content is about 96% and molecular weight distribution is rather broad. The value of α in the Mark‐Houwink viscosity equation for molecular weight Mη is determined as 0.70. The abnormal stress–relaxation behavior can be normalized by the introduction of an entanglement reduction factor, e.g., Mη/Mc for maximum relaxation time. This reduction is subsequently verified by evaluating the molecular weight dependence on bulk viscosity with 3.45th power. The starting of a yield process is equivalent to that of a disentanglement process, since both processes have approximately the same activation energy, 8 kJ/mol. For the onset of yield or of entanglement, the critical molecular weight Mc as estimated independently by yield strength method or by relaxation spectrum is equal to (5.4 ± 0.2) × 104. It is confirmed by the reduced yield strength method by calculating Me from the equation Me = 3gNρRT/EeN with gN = 1.22 and then by extrapolation, where EeN is the equilibrium modulus due to entanglement.
Pore size evaluation for fine porous freeze‐dried cellulose acetate membrane by gas separation
Authors: Tanioka A. , Ishikawa K. , Kakuta A. , Kuramoto M. , Ohno M. 
Published: April 2003

AbstractThe pore size for a fine porous freeze‐dried cellulose acetate membrane was evaluated by gas separation methods, where the Present–deBethune equation was applied. Separation coefficients were referred to the calculated value for each pore size from this equation. Nuclepore, Millipore VS, and Millipore VC, whose pore sizes were already known by bubble point method, were tested for this method. Pore diameters for this cellulose acetate membrane, thus determined, were about 25 and 40 Å from Ar–Kr and N2–Kr separation systems, respectively, which agreed well with the results from electron microscope (50 Å) and N2 gas permeability (50 Å). However, it is impossible to apply this method to He gas separation, since He gas permeability is higher than the expected value as Knudsen flow, which indicates that some channels are existing in this membrane, where He gas is more permeable than the other gases.
Modified acrylamide polymers for enhanced oil recovery
Authors: Khune G. D. , Donaruma L. G. , Hatch M. J. , Kilmer N. H. , Shepitka J. S. , Martin F. D. 
Published: April 2003

AbstractCopolymers of sodium acrylate and N‐methyl‐, N‐isopropyl‐, N‐n‐butyl‐, and N‐t‐butylacrylamide were prepared. The viscosities of these copolymers in 0.01% and 2.00% NaCl and their resistances to shear were compared with those of several partially hydrolyzed polyacrylamides. The poly(N‐alkylacrylamide‐co‐sodium acrylate demonstrated somewhat better retention of viscosity in brine than did analagous partially hydrolyzed polyacrylamides. N‐alkyl substitution increased sensitivity to shear in low salt solutions.
Viscoelastic and thermoelastic properties of general purpose commercial vulcanized natural rubber
Authors: Nishida Noboru , Murai Masaki , Sasaki Naoki 
Published: April 2003

AbstractViscoelastic and thermoelastic properties of general purpose vulcanized natural rubber were investigated focusing attention on its nonideal or irreversible natures. The master curve is not composed by simple horizontal shift of stress–relaxation curves at various temperatures by the time–temperature superposition principle. In order to compose a smooth master curve, both horizontal and vertical shifts are necessary. The relative stress–time relation elucidates the fact that the stress–relaxation mechanism is caused by the chemical scission by oxidation occurring in the network system. The value of vertical shift increases with increasing temperature or strain. This phenomenon has the same meaning as the one derived from the relative stress–time relation. The activation energies are calculated using the horizontal shift factors determined empirically. The result suggests the existence of two concurrent relaxation mechanisms with different activation energies. From the stress–temperature relation at any given strain, energetic and entropic components of the stress–strain curve are obtained. The energetic component is very significant as compared with the case of ideal crosslinked natural rubber. This phenomenon is considered to be caused by the internal friction and/or chemical scission of bonds in the system associated with the deformation process of sample.
Estimation of molecular weight averages from intrinsic viscosity
Authors: Chee K. K. 
Published: April 2003

AbstractThe weight‐average molecular weight is estimated by an extrapolation technique based on a linear relation between the viscosity‐average molecular weight Mv and a Mark–Houwink–Sakurada constant. This method may also be used to assess the unperturbed dimensions of polymers. If the Mv data are known with high accuracy, then the straight line may be stretched to reach the number‐average molecular weight confidently. The slope of the linear plot is associated with the molecular weight distribution and as such can be utilized to compute the polydispersity index.
Mechanism of void formation in cable covering
Authors: Titomanlio G. , Piccarolo S. 
Published: April 2003

AbstractSolidification after extrusion of coaxial cables has been experimentally simulated. Solidification tests were performed with two HDPE grades and under several pressures; the extrusion velocity was varied in a suitable range so as to detect the critical velocity for void formation. A qualitative analysis of the void formation mechanism is carried out, and the predicted trends favorably compare with the critical velocity data.
High temperature GPC of polypropylene
Authors: Grinshpun V. , Rudin Alfred 
Published: April 2003

AbstractThe highest temperature at which molecular weight distributions can be characterized by current techniques is 145°C. Supermolecular aggregates may exist at this temperature in polypropylene solutions in trichlorobenzene and other solvents. Dissolution procedures at higher temperatures are ineffective in this case because of the limited thermal stability of polypropylene. Aggregate‐free solutions can be prepared, however, by controlling storage times at 145°C in mixtures with added stabilizers. Low angle laser light scattering measurements can be used to determine when true solutions have been produced. This occurs when measured second virial coefficients agree with values predicted for the Mw measured in the light scattering experiment. GPC–LALLS measurements of Mw and Mz provide similar information about the effects of storage time on dissolution of aggregates and polymer degradation.
Blends of nylon 6 with an ethylene‐based multifunctional polymer. I. Rheology–structure relationships
Authors: Han Chang Dae , Chuang Hsiao‐Ken 
Published: April 2003

AbstractAn experimental study was conducted to investigate the rheological behavior of a heterogeneous polymer blend system consisting of nylon 6 and an ethylene‐based multifunctional polymer (CXA 3101, DuPont Co.). For comparison purposes, we also investigated the rheological behavior of two additional blend systems, namely blends of nylon 6 with a chemically modified polyolefin (Plexar 3, Chemplex Co.) and blends of nylon 6 with ethylene–vinyl acetate copolymer (EVA). We have investigated the thermal and thermomechanical behavior of the blend systems, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Also, we have attempted to identify the chemical structure of the functional groups present in the CXA 3101 and Plexar 3 resins, using infrared (IR) spectroscopy. This information has enabled us to interpret the observed rheological behavior. Furthermore, we have used both optical and scanning electron microscopies to investigate the state of dispersion of the constituent components in each of the blend systems. We have concluded that, during melt blending, chemical reactions have taken place between carboxyl or anhydride groups present in the CXA 3101 resin and the amino end groups of the nylon 6, forming a graft copolymer which then acted as an “interfacial agent.”
The effect of hygrothermal fatigue on physical/mechanical properties and morphology of neat epoxy resin and graphite/epoxy composite
Authors: Mijović Jovan , Lin King‐Fu 
Published: April 2003

AbstractThe effect of moisture absorption, desorption, and thermal spiking on the physical/mechanical properties of TGDDM/DDS epoxy resin was investigated and compared to the Gr/Ep composite. The mechanism of moisture diffusion in the neat resin was described on the morphological level. The diffusion rate of moisture in epoxy resin was found to depend on the mobility of molecular chains within an inhomogeneous epoxy network. Two well‐known concepts of plasticization of amorphous polymers, the lubricity theory and the gel theory, were invoked to describe the interactions between the absorbed moisture and the resin network. Slight permanent changes in properties of the neat resin were observed after one absorption‐desorption cycle. In the thermal spiking experiment, only the spiking temperature above the glass transition of the moisture saturated epoxy resins changed their internal structure and produced very small (thin) microcracks. By comparison with the neat epoxy resin, the Gr/Ep composites contain the reinforcement‐matrix boundary region, characterized by the highest restrictions to molecular mobility. The absorbed moisture during the static hygrothermal fatigue cannot effectively plasticize this region. But during thermal spiking, the formation of microcracks is observed within the reinforcement‐matrix boundary region as well as an increase in the moisture content.
Structure development in melt spinning poly(vinylidene fluoride) fibers and tapes
Authors: Wang Yimin , Cakmak Mukerrem , White James L. 
Published: April 2003

AbstractA series of poly(vinylidene fluoride)s of varying molecular weight have been melt spun to form fibers and tapes. These have been characterized with wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), birefringence, and small angle light scattering (SALS). WAXD and DSC have detected both the α and β crystal structures in melt spun fibers with the relative amount of β increasing with drawdown stress. WAXD and birefringence have been used to detect orientation in the fibers. Hermans–Stein orientation factors have been computed for the α‐phase as a function of drawdown stress. Superstructure has been investigated using SALS. The mechanical properties of fibers have been determined with a tensile testing machine and correlated with orientation and spinline stress.
Relationships between structure and mechanical properties of rubber‐modified epoxy networks cure with dicyanodiamide hardener
Authors: Bartlet Philippe , Pascault Jean‐Pierre , Sautereau Henry 
Published: April 2003

AbstractEpoxy network systems based on DGEBA and dicyanodiamide (DDA) and modified with a low molecular weight rubber (CTBN) were prepared and characterized. The kinetics of the adduct formation is followed using GPC analysis. The phase separation of the rubber phase is evidenced with DSC and SEM for all samples up to 20% CTBN. The GPC analysis of the soluble fraction demonstrates a chemical modification of the network. The mechanical properties and specially the impact strength behavior are enhanced with CTBN, but exhibit a maximum for 15% CTBN. In connection with SEM of fracture surfaces, these results are discussed and both modification of the rubber morphology and decrease in crosslinking density are taken into account.
Amidoxime‐group‐containg adsorbents for metal ions synthesized by radiation‐induced grafting
Authors: Okamoto J. , Sugo T. , Katakai A. , Omichi H. 
Published: April 2003

AbstractAmidoxime‐group‐containing fibrous adsorbents for metal ions were synthesized by radiation‐induced grafting of acrylonitrile followed by amidoximation of cyano groups with hydroxylamine. The degree of amidoximation and the distribution of amidoxime groups in the fiber were follwed by means of electron probe X‐ray microanalysis. The efficiency of adsorbing metal ions was increased by alkaline treatment of the adsorbent at high temperature for a short period before use. The order of adsorption for various bivalent metal ions was Hg > Cu > Ni > Co > Cd. From the distribution pattern of metal ions in the fibrous adsorbent, the adsorption was found to be controlled by the diffusion of the solution containing metal ions inside the adsorbent. It was found that confining amidoxime groups superficially and making short chain length of grafts were effective to obtain a high degree of adsorption.
The differential viscometer. I. A new approach to the measurement of specific viscosities of polymer solutions
Authors: Haney Max A. 
Published: April 2003

AbstractA new type of solution viscometer is described that measures the specific viscosity directly. This is accomplished with a balanced network of four capillaries arranged in a manner analogous to a Wheatstone bridge. A differential pressure transducer measures the increase in pressure across the bridge when a solution is injected into one of the capillaries while solvent flows continuously in the other three capillaries. The differential pressure is proportional to the specific viscosity of the solution. The differential viscometer is about 10 times more sensitive than a conventional glass tube viscometer, permitting precise measurements of specific viscosities of 0.01 or less. The measurements are also inherently fast, averaging about 3 min per sample. Precision is about 1% RSD. Accuracy was investigated by running standard solutions of sucrose in water, polystyrenes in toluene, and polyethylenes in decalin. The agreement was within 2–3% of the standard values in most cases.
Infrared spectra of poly(ethylene terephthalate) yarns. Fitting of spectra, evaluation of parameters, and applications
Authors: Heuvel H. M. , Huisman R. 
Published: April 2003

AbstractA quantitative model for fitting infrared spectra of polyethyleneterephthalate samples over the region from 1100 to 720 cm−1 has been evaluated. The absorbance was described as the sum of a linear base line and a set of symmetrical bell‐shaped Pearson VII curves. Using this model, experimental transmission spectra of yarns, measured with the electric vector parallel and perpendicular to the fiber axis, were fitted. It was found that each of the trans bands near 972 and 845 cm−1 consists of two components, a narrow and a broad one. These two components represent the crystalline and amorphous phases respectively. The band due to the out of plane benzene ring CH deformation vibration at about 875 cm−1 appeared also to be composed of two contributions. In this case, the narrow component was found to be due to molecules having interactions with direct neighbors. So this narrow component not only contains the molecules in the crystalline phase but also those forming part of bundles which are too small to be detected by x‐ray diffraction. For a detailed insight into the molecular arrangement of the amorphous regions, the infrared detection of trans‐guache transitions, fold content, detection of bundlelike structures, and molecular stress on tie molecules turned out to be of great practical importance. The structural details, which can be revealed by the infrared technique, cannot be obtained by other means. The potential of the method is illustrated with some practical examples.
“Equatorial small‐angle x‐ray scattering study of porosity and pore‐size distribution in polyester and their influence on dyeing behavior”
Authors: Kulshreshtha A. K. , Rao M. V. S. , Dweltz N. E. 
Published: April 2003

AbstractFor explaining the dyeing behavior of polyester (PET) fibers, the important role played by pores has been speculated upon in modern dyeing theories. In the present work, an attempt has been made to characterize the pore size spectrum in morphologically very different PET fibers by means of equatorial small‐angle X‐ray Scattering (SAXS). The analysis of the scattering curves reveals that all the samples analyzed in the present work have a two‐phase structure, consisting of pores of widely different sizes dispersed within a matrix of the polymer network. This polydispersity of pore sizes is revealed from Guinier plots, as well as from an analysis of intensities in the tail of the scattering curves, which are found to obey Porod's Law. Estimates have been made of pore radii, pore concentration in the substrate, and specific surface. The pore size distribution function has been obtained using a new procedure. Various parameters of the pore size spectrum are discussed in relation to the morphological structure of fibers, as well as their significance to dyeing. The diffusion behavior of solvent molecules within PET is also discussed.
Effect of curing agents on some properties of a polysulfide sealant
Authors: Ramaswamy R. , Achary P. Sasidharan 
Published: April 2003

AbstractThe effect of curing agents on the properties of a polysulfide sealant composition was investigated. Commercially used curing agents, namely, lead dioxide, manganese dioxide, and ammonium dichromate, were selected for this study. It was established that curing agents affect joint strengths, stress–strain properties, dynamic mechanical properties, and thermal stability of the sealant. Sealant cured with ammonium dichromate had highest shear bond strength, ultimate tensile strength, modulus, and thermal stability, whereas these properties were lowest for lead‐dioxide‐cured sealant. Peel bond strength and elongation at break were highest for lead‐dioxide‐cured sealant. The observed changes in properties were attributed to the difference in crosslink density of the cured sealant, produced by the curing agents. The curing agents have no appreciable effect on the fuel resistance of the polysulfide sealant.