bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and electrical properties of poly(vinyl benzoate) monolayers
Authors: Scala Luciano C. , Handy Robert M. 
Published: April 2003

AbstractThe structure and electrical properties of mono‐ and multilayer poly(vinyl benzoate) (PVB) films have been studied by using the films as ultrathin insulating spacers between evaporated electrodes of Cu and Sn. PVB–stearic acid mixtures were also used. Form capacity measurements, autoradiographs, and the layering conditions it is concluded that the compacted PVB film on the aqueous subphase has an average area per monomer unit of ∼8A.2 and is composed of several superimposed layers of molecules rather than a single layer. Usually each transfer operation yielded a PVB insulating film whose average thickness was estimated to be ∼37 A. Under certain and still unknown conditions, the PVB layer appeared to separate on transfer to give an average film thickness of approximately half of this value. The dielectric constant of the PVB films at room temperature and 1 keycle/sec. was estimated to be ∼3.3, and was found to be frequency‐dependent within the measured range of 100 cycles/sec. to 20 kcycles/sec. Conduction through the metal–PVB–metal sandwiches was highly nonlinear and was believed to take place by tunneling in the thinner films (∼20 A.) and by field‐assisted thermionic emission in the thicker films (∼75 A.). Interpretation of the conduction measurements in terms of a molecular model was not possible because of the wide variations in electrical properties and lack of reproducibility.
Characterization of polypropylene according to steady‐state flow behavior
Authors: Nakajima Nobuyuki , Wong Patrick S. L. 
Published: April 2003

AbstractCommercial samples of polypropylene were characterized in respect to their molecular weight and molecular weight distribution on the basis of quantitative information gained from their steady‐state flow behavior. The information obtained from this analysis was used to interpret the results of extrudate swelling, reinforcement of impact strength, and lowering of brittleness temperature. Manners of thermal and shear degradation were also studied.
Mechanical properties of crosslinked polyethylene and crosslinked ethylene–ethyl acrylate copolymers
Authors: Bonotto Sergio 
Published: April 2003

AbstractStress–strain curves at various temperatures and secant modulus vs. temperature curves were used to investigate the differences that exist between peroxide crosslinked polyethylene, and vulcanized rubber. A series of hypotheses in terms of crosslinking density and crystallinity is advanced to help visualize the differences between crosslinked polyethylene and cured rubber. The same techniques were used to investigate the nature of crosslinked ethylene–ethyl acrylate copolymers. These copolymers, being more flexible than polyethylene, appear similar to “mechanical rubber,” particularly after crosslinking. Recent experiments, however, indicate that profound differences exist. The performance of crosslinked polyethylene and of ethylene copolymers at elevated temperatures depends on crosslinking density, while at lower temperatures it is dominated by polyethylene crystalline morphology. This latter factor makes crosslinked polyethylene at ambient temperature a completely different product from vulcanized rubber. It also means that a crosslinked polyethylene will have lower crosslinking density than most rubber compositions of equivalent room temperature stiffness. A good indication of crosslinking density of crystalline polyolefins may be obtained by measuring mechanical properties such as modulus at elevated temperatures. Use of reactive co‐agents is effective in raising crosslinking density to the point where fairly good elevated temperature properties are obtained without increasing the room temperature rigidity.
Extrusion characteristics of poly(vinyl chloride)
Authors: Mayrick R. G. , Sieglaff C. L. 
Published: April 2003

AbstractThe general flow properties of poly(vinyl chloride) in a capillary rheometer have been compared to the flow behavior in a screw extruder. It was found that the flow behavior can be characterized by either method to within the experimental accuracy of the instruments. The viscosity of the melt in the extruder barrel was calculated from its pressure profile.
Infrared spectroscopic analysis of complex polymer systems
Authors: Sefton Michael V. , Merrill Edward W. 
Published: April 2003

AbstractA procedure has been developed for the analysis of complex polymer systems, using infrared spectroscopy. Its application to the analysis of styrene–butadiene–styrene triblock copolymers hydroxylated in the solid phase by reaction with peracetic acid is described. Twenty‐two frequencies of analytical interest were found sufficient to describe the infrared spectrum of the reacted polymer and were used to estimate the concentrations of the 12 components (functional groups) found to be present. A least‐squares solution of the Lambert‐Beer law equations was used to determine the 12 concentrations of interest. The errors associated with the regression and with the uncertainties in the determination of the absorptivities were determined using model compounds with the functional groups in approximately similar environments to those found in the polymer. With this procedure, the concentrations of the major components could be determined to within ±30%, which was sufficient to determine the effects of diffusion on the solid‐phase reaction process.
Isothermal rupture characteristics of a plasticized poly(vinyl chloride) in the glass–rubber transition zone
Authors: Smoley E. M. 
Published: April 2003

AbstractConstant strain‐rate uniaxial extension tests to rupture were performed at 23°C on a plasticized poly(vinyl chloride) (PVC) in the glass‐to‐rubber transition zone, Tg = −18°C, where experimental failure time tf is equal to or greater than material relaxation time τ. Range of strain rate is from 1.8 × 10−4 to 1.8 × 10−1 sec−1. The rupture characteristics in stress/strain time space are analyzed on the three coordinate planes. Time and deformation separability are examined in a nonlinear‐constitutive relation. Rupture data on the coordinate planes are described by the Bueche‐Halpin theory in which time effects are considered through a small‐deformation viscoelastic property. Fracture surface morphology and separation processes in the crack tip are related to rupture characteristics.
Effect of styrene grafting on diffusion and solubility of gases in polyethylene
Authors: Toi Keio , Igarashi Kiyoshi , Takuda Taneki 
Published: April 2003

AbstractDiffusion and solubility coefficient data of gases for styrene‐grafted high‐density polyethylene obtained by γ‐irradiation are reported. Diffusion coefficients were determined by the time lag method. Solubility coefficients were determined by a new, more accurate static method. Densities and volume fractions of grafted polystyrene were calculated from the observed values of extent of grafting and density of the graft copolymer films. The solubility coefficients obey simple additivity in terms of volume fraction of side‐chain polystyrene and amorphous polyethylene. However, behavior of the diffusion coefficients is more complex. Inasmuch as diffusion is a kinetic process, it is influenced by morphology. The experimental results reported here, together with x‐ray diffraction and DSC data, provide a basis for discussing the morphology of the graft copolymers.
Preparation and properties of fibers from a crystalline polymethacrylonitrile
Authors: Miyanoki Masahiko , Joh Yasushi 
Published: April 2003

AbstractFibers from a crystalline polymethacrylonitrile were prepared by dry spinning using trifluoroacetic acid as solvent. Stretchability increased when the solvent retained in the fiber was extracted with methanol. Tensile properties are well acceptable for practical use. It is notable that the stress–strain curve for the polymethacrylonitrile (PMAN) fiber shows clear yield point even under hot‐wet condition (90°C in water). Thus, the PMAN fiber is expected to have improved “hot‐wet properties” compared with conventional acrylic fibers. From the data in the compliance and resiliency maps, the PMAN fiber is expected to be one of the most promising fibers having wool‐like properties.
Thermodynamic and mechanistic characterization of water sorption in homogeneous and asymmetric cellulose acetate membranes
Authors: Burghoff H. G. , Pusch W. 
Published: April 2003

AbstractThe water sorption isotherms for homogeneous and asymmetric cellulose acetate membranes have been measured at different temperatures. Subtle differences between the water sorption isotherms for asymmetric and homogeneous membranes have been interpreted by suggesting that capillary condensation contributes significantly to sorption in asymmetric membranes at high activities and also to an intriguing excess sorption observed in homogeneous membranes at intermediate activities. This model has been supported by the experimentally determined values of the enthalpy and entropy changes associated with sorption.
Initial flux decline and initial rejection increase for swollen ionic membranes
Authors: Van Der Velden P. M. , Smolders C. A. 
Published: April 2003

AbstractDuring the initial stage of operation, membrance performance in hyperfiltration experiments will be time dependent. For swollen ionic membranes, fluxes show an initial decrease while rejections initially increase in magnitude. These phenomena, also referred to as compaction, can be described by a model proposed here in which the wet membrane thickness decreases in time as a combined response to stepwise changed process parameters pressure and concentration. The response has been described by a linear first‐order differential equation and worked out by use of known concepts of flux and rejection for swollen ionic membranes. Experimental data appear to be in good agreement with model predictions.
A world‐wide program for the continuous monitoring of solar UV radiation using poly(phenylene oxide) film, and a consideration of results
Authors: Davis A. , Deane G. H. W. , Gordon D. , Howell G. V. , Ledbury K. J. 
Published: April 2003

AbstractThe use of poly(phenylene oxide) film to monitor UV radiation is demonstrated, and the results from the continuous monitoring of solar UV radiation at 24 sites throughout the world are presented. The global and diffuse measurements from a temperate and from a tropical site are analyzed in detail, and the effects of season and weather conditions on the UV contribution to solar radiation and the relative importance of the diffuse and direct components of solar UV are discussed.
An analysis of unsteady one‐dimensional stretching of a viscoelastic fluid
Authors: Ting R. Y. 
Published: April 2003

AbstractThe time‐dependent response of a viscoelastic liquid to unsteady one‐dimensional stretching deformations was examined. Oldroyd's three‐constant model for a viscoelastic fluid was used. Two cases representing two different stretching histories were analyzed: a sine stretching pulse and a step stretching pulse. The results show that high elongational viscosity may be easily reached in both cases. As the relaxation time of the liquid becomes comparable to the pulse width, elongational viscosity increases with the increase in maximum stretching rates. Conditions to maintain high levels of elongational viscosity at a subsequently reduced stretching rate were given as functions of the relaxation time and initial stretching rates. In view of recent turbulent boundary layer data, the results were used to discuss possible explanations of turbulent drag reduction in polymer solutions. It was concluded that the basic mechanisms for drag reduction in polymer soluations. It was concluded that the basic mechanisms for drag reducation may be related to the effects of high elongational viscosity and local stabilization of small shear disturbances.
Shear degradation of polyisobutene
Authors: Abbås Kent B. , Porter Roger S. 
Published: April 2003

AbstractA polyisobutene of M̄w 1.98 × 106, M̄w/M̄n 1.8, was extruded in an Instron capillary rheometer. Shear degradation occurred at high shear stresses, approaching melt fracture, and was more prominent at lower extrusion temperatures for tests at 60–140°C. The capillary was 2.0 in. long with a length/diameter ratio of 66.7 and a 90° entrance angle. Repetitive extrusions at constant shear rate caused a decrease in a molecular weight and a simultaneous narrowing of the molecular weight distribution. Extrudate expansion was measured after each successive capillary pass for tests at 80°C. Extrudate swelling correlated well with (M̄z+1) M̄z/M̄w, except for the two first passes, where melt fracture was pronounced. The correlation with equilibrium extrudate expansion was almost as good for (M̄z/M̄w)3.7 (Mill's correlation) and for M̄z+1 alone. The efficiency of bond rupture is low, with the energy required to rupture 1 mole of bonds being about 200,000 kcal at 80°C.
Polystyrene degradation in model extrusion experiments
Authors: Abbås Kent B. , Porter Roger S. 
Published: April 2003

AbstractAn investigation has been made of the magnitude and the source of degradation of polystyrene in model extrusion experiments. A preformed solid plug of a narrow‐distribution, high molecular weight polystyrene (M̄w = 2 × 106) was used for each experiment. The extrusions were performed with an Instron capillary rheometer at constant temperatures from 160° to 220°C. The molecular weight changes occurring in the capillary reservoir during the pass of the capillary and in the hot extrudate were evaluated. Molecular weights and distributions were obtained by gel permeation chromatography. A significant degradation was observed in the capillary reservoir. The degree of degradation was independent of polymer flow. The polystyrene near the walls reacted more extensively than that closer to the axis, but a constant degradation was observed along the axis. The molecular weight profile across the capillary reservoir was attributed to a selective thermo‐oxidative degradation (160° and 190°C). Changes in molecular weight due to mechanical degradation in the capillary were observed only at 160°C. This reaction was referred to as a mechano‐oxidative process, as no degradation could be detected in the absence of oxygen. At 160°C, selective migration of macromolecules (fractionation) during extrusion did not occur to any significant extent, nor could any thermo‐oxidative degradation of the extrudate be detected. When a small amount of antioxidant (Ionol) was added to the polystyrene, no selective degradation did occur at the walls of the capillary reservoir during extrusion at 160° and 190°C.
Studies in swelling of cotton. I. Neutral salt technique to determine the true swelling parameters in cadoxen
Authors: Achwal W. B. , Joshi S. M. , Karmakar S. R. 
Published: April 2003

AbstractThis paper describes the swelling of cotton fiber in cadoxen containing 4.6% cadmium (w/w) and 30% ethylenediamine (w/w). A special neutral salt technique is described involving the analysis of extract as well as mother liquor which enables the determination of mechanically held liquor and hence the values of true absorption. The percentage true weight swelling values are much lower than the percentage apparent weight swelling as measured by centrifuge technique. The effect of variation in material‐to‐liquor ratio on the true absorption of cadmium and ethylenediamine is also investigated.
An investigation of the effects of the molecular weight distribution on the sensitivity of positive electron resists
Authors: Lai Juey H. , Shepherd Lloyd 
Published: April 2003

AbstractThe molecular weight distribution of two grades of poly(methyl methacrylate) was determined, and the solubility of that polymer in methyl ethyl ketone–2‐propanol mixtures was studied. The effects of the molecular weight distribution of the polymer and the strength of the developing solvent on electron resist sensitivity were studied experimentally and compared with a computer model of the electron exposure process. The molecular weight and the molecular weight distribution were found to have a significant effect on the sensitivity of poly(methyl methacrylate) as an electron resist. Increased sensitivity is predicted for higher molecular weight and narrower molecular weight distribution.
On the thermal degradation of poly(vinyl chloride). IV. Initiation sites of dehydrochlorination
Authors: Abbås K. B. , Sörvik E. M. 
Published: April 2003

AbstractA set of poly(vinyl chloride) samples were investigated with respect to their thermal stability. The dehydrochlorination rates were measured in nitrogen at 190°C by use of a very accurate, conductometric method. For all polymers studied, a significant molecular weight increase was observed after 0.4% conversion. With only one exception, samples exhibiting higher degradation rates showed higher absorptions (350–450 nm) after 0.4% dehydrochlorination. In addition, the relative amount of short polyene sequences was found to be higher for polymers with higher degrees of branching. The dehydrochlorination reaction was predominantly initiated at sites of internal unsaturation (allylic chlorines), but an initiation at tertiary chlorines and unstable end‐groups could not be completely omitted. Head‐to‐head units, extraneous impurities, and syndiotactic sequences were found to be of minor importance in this respect.
Electron spectroscopy for chemical analyses (ESCA)—A tool for studying treated textiles
Authors: Soignet D. M. , Berni R. J. , Benerito R. R. 
Published: April 2003

AbstractElectron spectroscopy for chemical analysis (ESCA) has been successfully used to determine the location of flame‐retardant polymers or reagents and crosslinking and oil/water‐repellent reagents in relation to fiber surfaces of chemically modified cotton fabrics and cotton/polyester blends. Changes in intensity of characteristic ESCA element signals were followed as the particle size of the treated fabric varied. Dimethyloldihydroxyethyleneurea (DMDHEU) and the flame‐retardant polymer formed from tetrakis(hydroxymethyl)phosphonium chloride (Thpc) and urea penetrate and are homogeneously deposited throughout cotton fabrics. The oil/water‐repellent finish, FC‐218, and the flame retardants from the THPOH/NH3 reaction and tris(dibromopropyl) phosphate are deposited on the surfaces of both cotton and polyester fibers.
The viscosity of monomolecular melts of poly(vinyl chloride)
Authors: Lyngaae‐Jørgensen J. 
Published: April 2003

AbstractPVC melts are predicted to be homogeneous with single molecules as the stable flow units (monomolecular melts) at corresponding values of high temperatures and/or high shear stresses. Under these conditions, it is found that the zero shear viscosity in simple shearing flow of rigid compounds depends on the average molecular weight by weight to the 3.5 power for molecular weights between 24,000 and 100,000. All data measured under conditions where monomolecular melts are predicted fall on a master curve of reduced viscosity versus reduced shear rate when a relaxation time proportional to η0/c2T is used. It is, therefore, concluded that monomolecular melts of PVC compounds follow the same structure–viscosity relations as found for other linear melts in viscometric flow.
Diffusion of stabilizers in polymers. III. 2,4‐dihydroxybenzophenone and 2‐hydroxy‐4‐octoxybenzophenone in polyurethanes
Authors: Hauserman R. G. , Johnson M. 
Published: April 2003

AbstractThe diffusion of the radioactively labeled ultraviolet stabilizers 2,4‐dihydroxybenzophenone and 2‐hydroxy‐4‐octoxybenzophenone in two linear poly(ester‐urethanes) was studied over the temperature range 36–75°C. Within this temperature range, both stabilizers diffused faster in the polyurethane which had a polyester of molecular weight 2000 in its chain rather than in the polyurethane with a polyester of molecular weight 1000 in its chain. 2,4‐Dihydroxybenzophenone diffused slightly faster than 2‐hydroxy‐4‐octoxybenzophenone in both polyurethanes. In each case, the results can be represented by an Arrhenius expression D = D0 exp (−E/RT). The values of D0 and E are discussed in terms of the size of the stabilizer molecular and the structure of the polymer.
Collagen as a biomaterial: Modulus jump and degradation of collagen gels
Authors: Zvanut Carl W. , Rodriguez Ferdinand 
Published: April 2003

AbstractThe effect of temperature on the storage modulus G′ of UV crosslinked collagen has been investigated. Collagen solutions, 0.5%, at pH 2.2 were irradiated at 4°C to a maximum modulus, after which they were stored at 4°C. In order to study the effect of temperatures above 4°C, the gels were placed in a constant‐temperature bath and the change in modulus with time was recorded using a torsion pendulum. The temperatures studied ranged from 25° to 60°C. The results show an initial jump in modulus immediately on heating presumably due to the helix‐coil transition. The modulus goes through a maximum value. There is then a decay of modulus with time which is linear on a semilog plot. This could indicate a first‐order chain‐scission reaction, since the storage modulus is directly proportional to the number of crosslinks. A simple kinetic expression can be written for which the value of the rate constant can be determined from the data.
Diffusion in aqueous polymer solutions
Authors: Farag A. A. , Farag H. A. , Sedahmed G. H. , El‐Nagawy A. F. 
Published: April 2003

AbstractThe diffusion of Direct Blue 76 dye in aqueous dilute polymer solutions was studied using the capillary method. The polymer systems studied included dilute solution of carboxymethyl cellulose, poly(ethylene oxide), and polyacrylamide. It was found that the diffusion coefficient of Direct Blue 76 in carboxymethyl cellulose is higher than that in pure water, while in polyacrylamide and poly(ethylene oxide) solutions the value is lower than that in pure water. The diffusion coefficient of Direct Blue was found to decrease with increasing polymer concentration in case of poly(ethylene oxide) and polyacrylamide, while in case of carboxymethyl cellulose the diffusion coefficient increases with polymer concentration. The effect of temperature on the diffusion coefficient of Direct Blue 76 in the three polymers was found to obey the Arrhenius equation. The activation energy for diffusion of Direct Blue 76 in water, poly(ethylene oxide), polyacrylamide, and carboxymethyl cellulose was found to be 4.38, 7.7, 5.44, and 5 kcal, respectively, for polymer concentration of 0.25 g/l.
Water‐soluble polymers as retention aids in a model papermaking system. IV. Some block and graft copolymers
Authors: Howard G. J. , Hudson F. Lyth , West Jeremy 
Published: April 2003

AbstractIn an attempt to relate the retention behavior of water‐soluble polymers in paper formation from cellulose fibers and titanium dioxide, several copolymer types were synthesized. These were acrylamide–acrylonitrile random copolymers; block copolymers of acrylamide, acrylonitrile, and 2‐vinylpyridine with poly(ethylene oxide); and acrylamide graft copolymers of ethyl hydroxyethyl cellulose. Good retention and heteroflocculation behavior is shown only by the first of the above types of copolymers. Generally speaking, block copolymeric structures synthesized were of molecular size too small to act as good retention aids, although in a number of cases their performance was noticeably superior to that of the homopolymer analog. Adsorption isotherms are also reported and the overall results discussed in terms of a polymer bridging mechanism of heteroflocculation.