bluuebunny/crossref_metadata_2025_split huggingface dataset:
The interpretation of high resolution electron micrographs of the cellulose elementary fibril
Authors: Hanna Robert B. 
Published: June 2010

AbstractSome of the present evidence for the structure of the celluiose elementary fibril may be attributed to artifacts. The factors involved in the production of these artifacts may include the phenomenon of phase image granularity, the thickness of the ultrathin section, the structure of the negative stain, and the nature of the substrate. Interpretation of high resolution electron micrographs requires an intimate knowledge of these factors.
Some problems in radiation grafting to cellulose fibers
Authors: Sakurada I. , Okada T. , Kaji K. 
Published: June 2010

AbstractIn the case of grafting by preirradiation method, the presence of air during preirradiation by gamma rays has practically no influence on the percent grafting, whereas the presence of water decreases the activity to a great extent. ESR studies of preirradiated cotton and rayon show that the active species for the grafting are not peroxides but free radicals even when the irradiation is carried out in air. The number of scissions of chemical bonds of the cellulose molecule by the irradiation is found to be practically independent of the degree of polymerization and microstructure of the initial cellulosic fiber; the presence of air also has no effect on the degradation. In the case of styrene grafting, breaking strength of single fibers remains substantially unchanged by the grafting, but the increase of denier by the grafting results in a drop of tenacity (g/den) of the single fibers. It is true that cellulosic fibers become hydrophobic by the grafting of styrene, but the tendency to absorb water calculated on the cellulose basis increases by the increasing percent graft. This may be the reason for the rather low wet tenacity of the styrene grafted cellulosic fibers.
Chromatographic and ion exchange properties of radiation copolymerized celluloses
Authors: Dilli S. , Garnett J. L. , Martin E. C. 
Published: June 2010

AbstractThe potential of radiation copolymerized celluloses in chromatography, particularly in the reversedphase technique is discussed. A range of styrenated celluloses has been prepared from copolymerizing styrene with Whatman 40, 41, and 42 papers. The effect of percent styrene on the separation characteristics of a number of dyestuffs on these grafted papers has been studied. Significant differences in chromatographic behavior of the dyes is observed between the grafted and nongrafted papers. Similar changes in RF values between the two types of papers are also observed for the separation of a range of 19 typical cations. Detailed studies have been performed particularly with Zn+2, NI+2 and Cd+2. In the separation of the fatty acids, stearic, myristic and lauric, the grafted celluloses are shown to possess advantages over the untreated Whatman equivalent. For column chromatography, a methylmethacrylate‐cellulose radiation copolymer has been used to quantitatively separate a mixture of oil soluble dyes. This same mixture could not be separated on a column of untreated cellulose powder. Finally the ion exchange properties of grafted copolymers where the monomer contains a functional group such as −NH2, −SO3H or even a heterocyclic nitrogen (the vinyl pyridines) are discussed.
Deformation behavior of amorphous film of nylon 11 and some other polyamides above and below the glass transition temperature
Authors: Northolt M. G. 
Published: June 2010

AbstractThe deformation behavior of initially amorphous films of nylons 11, 66, and 12 has been studied at drawing temperatures above and below the glass transition temperature. Evidence has been found that the glass transition temperature in polyamides is connected with a disruption of the hydrogen‐bonded network. In addition these experiments indicate that the kind of hydrogen‐bonded network present in the crystalline state determines whether the orientation of the crystallites in film specimens drawn below the glass transition temperature is uniaxial or biaxial.
Influence of thermal history on the melting behavior of isotactic polystyrene
Authors: Overbergh N. , Berghmans H. , Smets G. 
Published: June 2010

AbstractMultiple melting transitions of thermally crystallized isotactic polystyrene were studied. This behavior was attributed to a very rapid reorganization during the melting of the crystalline structure originally formed. From differential scanning calorimetry and optical microscopy it was shown that the rate of reorganization decreases with increasing reorganization temperature TR. This reorganization will only occur if its rate is larger or equal to the scanning rate. A TR value can be defined for each scanning rate and the resulting melting temperature TRM increases when the scanning rate decreases. This increase of TRM is also examined by annealing at different temperatures. A linear relationship between TRM and TR is observed and gives an extrapolated equilibrium melting point of 240°C; moreover the slope is smaller than for isothermal crystallization (TM versus TC). These phenomena are confirmed by optical microscopic observations.
Morphological changes during annealing of doubly oriented polycaprolactam
Authors: Baldrian J. , Pelzbauer Z. 
Published: June 2010

AbstractDoubly oriented polycaprolactam films were annealed with the ends free at temperatures between 145 and 200°C for 30 min. As the annealing temperature rose the long period increased, the transverse dimensions of fibrils grew anisotropically, and the low‐angle diffraction intensity and density also increased. On the other hand, there was a decrease in the breadth of crystalline reflections. During annealing the film shrank in the direction of the fibril axis (M) and expanded in the direction (N) in which the pressure was acting during the production process. No changes could be observed in the direction normal to the MN plane. The supermolecular structure was also investigated by means of electron microscopy. The phenomena observed are explained in terms of the Peterlin two‐stage model of plastic deformation of the crystalline polymers, which assumes the formation of strongly extended fibrils, connected by interfibrillar “tie” molecules.
Properties of vinylpyrrolidone‐methyl methacrylate statistical copolymer in mixed solvents
Authors: Bakauova Z. H. , Bekturov E. A. , Bereza S. V. 
Published: June 2010

AbstractIntrinsic viscosities of fractions of the statistical copolymer of vinylpyrrolidone and methyl methacrylate (composition 42:58 mole percent) have been measured in the cross‐selective solvents, benzene and methanol, in mixtures of these solvents, as well as in chloroform, a solvent for both polymer components, and in mixtures of chloroform with methanol. The dependence of the intrinsic viscosity on the composition of the mixed solvent exhibits a maximum reflecting the destruction of secondary structures that exist in the selective solvents. The temperature dependence of the intrinsic viscosity, which has a maximum around 50‐60°C, has been studied in chlorobenzene between 10° and 100°C. The Mark‐Houwink‐Kuhn constants K and a, which do not change significantly with solvent composition, have been calculated. The values of the parameters Kθand σ, which depend on solvent composition similarly to the intrinsic viscosity, have also been determined. The results indicate marked changes of macromolecular conformation from the hypercoiled structure in a selective solvent to the random coil in mixed and nonselective solvents.
The transport of water through latex films
Authors: Vanderhoff J. W. , Bradford E. B. , Carrington W. K. 
Published: June 2010

AbstractUpon drying, latexes are transformed from milky, colloidal dispersions to transparent, continuous films in which the contours of individual coalesced particles can still be discerned. Upon ageing at room temperature, however, these latex films undergo a further gradual coalescence in which the particle contours gradually disappear and any imcompatible substances (e.g., emulsifer) are exuded to the surface. With this point of view in mind, the rate of drying at 72°CF and 50% RH was measured for three copolymer latexes: 70:30 vinylidene chloride‐n‐butyl acrylate, 67:33 ethyl acrylate‐methyl methacrylate, 67:33 styrene‐butadiene. The drying process can be divided into three stages: (1) an initial constant rate stage which persists to 60–75 vol% polymer; (2) an intermediate stage in which the rate drops off rapidly to a value 10–20 times smaller; (3) a final stage in which the rate is very much smaller and decreases very slowly with time. These stages can be correlated with the mechanism of film formation: (1) in the first stage, the particles move about with their characteristic Brownian motion, and the water evaporates from the latex at the same rate as for pure water or dilute emulsifier solution; (2) the intermediate stage begins when the particles come into irreversible contact with one another and ends with their coalescence to form a continuous film: during this stage the rate of water evaporation decreases because the water‐air interfacial area is decreasing; (3) in the final stage, the water remaining in the film escapes by diffusion, either through capillary channels between the deformed spheres or through the polymer itself. Measurement of the liquid water and water vapor transmission rates of latex film samples, taken either at the end of the intermediate stage or after sufficient ageing to ensure completion of the further gradual coalescence, showed that the rate of water loss in the final stage is initially representative of diffusion through capillary channels, but slowly and asymptotically approaches a value representative of diffusion through the polymer, presumably reaching it within the time required for completion of the further gradual coalescence (about 14 days for these copolymers). The values obtained for the three copolymers are 6.2 × 10−7, 2.9 × 10−5, and 4.4 × 10−5 g‐mil/min/cm2, respectively, in reasonable agreement with values reported in the literature for similar but not identical polymers. The values for the liquid water and water vapor transmission rates were the same.
General statistics and Markov statistics of binary vinyl copolymers with asymmetric α‐carbon atoms
Authors: Gronski Wolfram , Klesper Ernst , Cantow Hans‐Joachim 
Published: June 2010

AbstractThe statistics of binary copolymers formed by polymerization of asymmetrically substituted α‐olefines is considered. On the basis of the principle of stationarity, the general statistical relations valid for binary systems are extended to these copolymers. Necessary relations between observable probabilities of sequences are given, covering also the case where only one of the two different monomer units may possess an asymmetric center. Moreover, the outlines of second order Markov statistics for copolymers possessing asymmetric centers are formulated.
Synthesis and physical properties of graft copolymers derived from phyllosilicates: I. The chrysotile and vermiculite derivatives
Authors: Zapata L. , van Meerbeek A. , Fripiat J. J. , Faille M. Della , van Russelt M. , Mercier J. P. 
Published: June 2010

AbstractIn this work a new class of composite polymeric materials was described. They were obtained by grafting vinylic polymer chains onto the vinylic derivative of the phyllosilicates. These composite materials are characterized by outstanding mechanical properties, especially by a high modulus of elasticity.
Molecular uniform macromolecules of polyamide 6
Authors: Craubner Hans 
Published: June 2010

AbstractThe molecular weight distribution (MWD) of an autoclave‐polymerized polyamide 6 (PA 6) was determined by solution fractionation to be a mixed distribution, consisting of three regions. The top corresponds to a small fraction of low molecular weight (∠ 1%) and the tail, to a small, weakly crosslinked component of high molecular weight (∠ 1%). Cutting the wings of the distribution by fractionation yields linear PA 6 fractions with an extreme narrow partial distribution accounting for more than 98% by wt. The linear molecular weight averages areMn, lin= 24,800 andMω, lin= 24,810. The nonuniformity isU= 0.3 × 10−3(compared toUPoisson= 4.6 × 10−3). The fractionation efficiency amounts to ϕ = 99%.A distribution function for the molecular uniform PA 6 is given. Kinetic considerations are discussed. As is shown, the molecular uniformity is then appreciably larger than that of, for example, aPoissondistribution (more than a power of ten), if the rate of the initiation reaction (ki) is appreciably larger than that of the propagation of the chain (kω):r = kω/ki≪ 1.The extreme narrow linear PA 6 distribution found by solution fractionation is confirmed by fast turbidimetric titration according to dynamic volume pulse technique. Furthermore, the results are supported by the recovery and the evaluated mean properties, such as intrinsic viscosity, melting points and endgroup molecular weight (MW).
Spectroturbidimetric titration of polymer solutions
Authors: Klenin V. J. , Shchyogolev S. Yu. 
Published: June 2010

AbstractA new modification of the method of turbidimetric titration based on taking the turbidity spectrum in the process of titration (accordingly designated “spectroturbidimetric titration” (STT)) has been proposed. STT permits the mass of the precipitated polymer Mγ to be determined in the process of titration with any change in the degree of dispersity of the precipitated polymer phase. The standardized plotting of the curve of solubility (CS) Mγ/(Mγ)max = f(γ), where γ is the volume ratio of the precipitator, proved to be independent of the nature of possible variation of the relative refractive index of the particles m = m (γ). STT was carried out with the commercial type of polystyrene (PS) (benzenemethanol) and withanionic poly‐α‐methylstyrene(P‐α‐MS) (cyclohexane‐octanol)in the serial turbidimeter FET. The turbidity was measured using five light filters at 4000–6000 Å. The speed of stirring was 64 rpm. Four rates of the precipitator input: W = 0.09, 0.20, 0.41, and 1.03 ml/min were used. Worse reproducibility of the colloid system structure in parallel experiments was found under low W correlated to the best division according to molecular weights. The STT method balanced these two antagonistic principles (like some others, though). Dependence on W of CS has been found. Graphic extrapolation of CS (with fixed Mγ% and W → 0) permitted the equilibrium CS to be determined. In a typical case three characteristic ranges of particles size changing in the process of titration were observed: decreasing (a reduction in gigantic fluctuations), a stable range, and increasing (particles coagulation). The colloid system structure may be regulated by selection of tiration conditions.
Characterization of poly (vinyl chloride) prepared by radiation‐induced bulk poly‐merization at temperatures from −50° TO 90°C
Authors: Carenza M. , Palma G. , Tavan M. 
Published: June 2010

AbstractOsmotic, viscometric, and light scattering measurements have been carried out on poly (vinyl chloride) samples, obtained by bulk polymerization on exposure to 60Co γ‐rays at dose rates varying over a 100‐fold range and at regularly spaced temperatures from −50 to 90°C. While with the samples prepared at the higher temperatures, solutions could be conveniently made in tetrahydrofuran, cyclohexanone appeared to be a more suitable solvent when polymerization temperatures from 10°C downwards were concerned. Furthermore, with the latter cases, strong heating treatments of the solutions were required. Correlations among the various parameters, deduced from the measurements, were examined and found in agreement with reported relationships for conventional poly (vinyl chloride). The patterns of gradual change of molecular weight with changing polymerization conditions were discussed.
Automated characterization of molecular properties of uncharged polymers
Authors: Keiner J. A. 
Published: June 2010

AbstractA growing battery of methods has become available in recent years for characterization at a molecular level of natural and synthetic polymers. Several methods are now available with automatic or semi‐automatic operation, suitable for routine or on‐line use and are so used in the polymer industry. The methods for characterization are critically reviewed, emphasizing methods now suitable for routine use in the laboratory or in industry, i.e., infrared spectroscopy, viscometry, osmometry, and gel chromatography.
Transient electric optical rotation for macromolecular characterization
Authors: Jennings B. R. , Baily E. D. 
Published: June 2010

AbstractIn an electric field, the optical rotation of a solution or suspension of helical molecules may be expected to change. Such changes are reported herein for solutions of poly (benzyl‐L‐glutamate) (PBLG) in ethylene dichloride using pulsed electric fields. These measurements enabled the molecular geometry to be evaluated (through the determination of a rotary diffusion constant) simultaneously with the determination of the molecular optical rotation components along the principal molecular axes. Fields were applied parallel to the light beam. Very dilute solutions were studied owing to the use of a stable laser as the light source plus the introduction of a special multiple cell in which the optical path length could be increased while maintaining the field strength. A dilute solution (0.1%) of PBLG gave rotation data in agreement with previously published data. In addition, the helical length and molecular weight were determined from the relaxation effect. Studies on concentrated solutions indicated the presence of aggregation. This highlights the need for caution in improving the observable optical rotation simply by increasing the solution concentration. The apparatus is described in outline and the advantages of this novel transieat method are listed.
Light scattering rayleigh linewidth measurements on some macromolecular solutions
Authors: Sellen D. B. 
Published: June 2010

AbstractSome light scattering Rayleigh linewidth measurements upon three globular proteins: chymotrypsinogen, bovine plasma albumin, and urease, are described. Measurements were made in 0.2 M NaCl and the diffusion constants calculated showed no concentration dependence. The measurements agreed well with theoretical predictions both as regards angular variation and frequency distribution.
On the mechanism of photoaging of poly‐caproamide
Authors: Pariiskii G. B. , Postnikov L. M. , Ya. Toptygin D. , Ya. Davydov E. 
Published: June 2010

AbstractThe photoaging of polyamides is commonly accepted to be a free‐radical process. It has been assumed1–3 that under action of ultraviolet light the macromolecules may decompose either along the C‐H or the C‐N bonds to macroradicals. The latter may enter a number of secondary processes mutually determining the change of chemical properties of the polymers. Studies of the nature of light‐generated free radicals with the ESR method have been reported earlier,1,3,4 but the interpretation of the results is quite ambiguous, and the ESR signals observed may be due to the secondary radicals being insensitive to the action of light. A possibility of phototransformation of the radicals in a γ‐irradiated polycaproamide has been noted.The present work is concerned with the study of the effect of the spectral pattern of the light upon the radical nature in pure nylon 6. On the other hand a mechanism is proposed for the phototransformation of radicals established at the photolysis of nylon 6 in the presence of iron chloride additives.
Studies of decomposition of polymer blends by thermogravimetric method
Authors: Mucha M. , Kryszewski M. 
Published: June 2010

AbstractStudies of thermal degradation in nitrogen atmosphere of homopolymers: polypropylene (PP), polyethylene (PE), poly(vinylidene chloride) (PCVD), and polyacrylonitryle (PAN) as well as of their blends were carried out using the thermogravimetric method. The investigations performed at different heating rates led to thermogravimetric curves which made it possible for the kinetic parameters characterizing thermal degradation, i.e., activation energy E and reaction order n, of the homopolymers and polymer blends in dependence on blend composition to be determined. PP and PE blends show higher thermal stability as compared with pure PP in contrast to the results obtained for PCVD with PAN blends.
Mechanism of catalytic acid hydrolysis of aromatic polyimides and relevant polyamic acids
Authors: Nechaev P. P. , Moiseev Yu. V. , Zaikov G. E. , Vygodskii Ya. S. , Gerashchenko Z. V. 
Published: June 2010

AbstractThe kinetics of catalytic acid hydrolysis of N‐phenylphthalimide, N‐phenylphthalamic acid (model compounds of polyimide and polyamic acids), and of certain soluble polyimides have been studied. A reaction mechanism is proposed implying that unreactive forms of the reactant appear by protonization of the amide bond at the carbonyl oxygen and by dissociation of the o‐carboxyl group (in case of N‐phenylphthalamic acid). Attack of the nonprotonized amide bond by hydroxonium ions is suggested to be the rate limiting step. A method for determining the cyclization extent of soluble polyimides to within 0.1% is proposed. The effect of structure on the chemical stability of polyimides has been studied.
Laser excited raman spectroscopy of synthetic polymers
Authors: Boerio F. J. , Koenig J. L. 
Published: June 2010

AbstractRecent advances in instrumentation for Raman spectroscopy are described. The fundamental differences between infrared and Raman spectroscopy are discussed and related to differences in selection rules, sampling techniques, and applications. The use of Raman spectroscopy for polymer characterization is illustrated by the results of recent research. The investigation of crystal structure is demonstrated by results obtained for polyethylene and orthorhombic polyoxymethylene. Detection of conformational changes in crystalline polyvinylidene fluoride and in solutions of polyethylene oxide by Raman spectroscopy is described as is determination of the composition of methyl methacrylate‐glycidyl meth‐acrylate copolymers.
Brillouin spectroscopy of macromolecular solutions
Authors: Nordhaus D. E. , Kinsinger J. B. 
Published: June 2010

AbstractBrillouin spectroscopy was evaluated as an experimental method for measuring the molecular weights of macromolecules. This evaluation included an examination of instrumental parameters, sample preparation, and spectral analysis. The Brillouin peaks were found to be independant of solute concentration for dilute solutions, in accordance with the assumptions of Miller's approximate theory. This theory was used to calculate molecular weights of five standard polystyrene samples. These values compared well with molecular weights derived from regular photometric light scattering and viscosity measurements.