bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of polyethylene single crystals
Authors: Giordano Orsini P. , Marchese B. , Mazzarella L. 
Published: April 2003

AbstractAn electron microscope study of polyethylene single crystals is reported. The following points have been investigated: (1) influence of crystallization temperature on crystal shape; (2) effect of solvent etching on already formed crystals. Crystals were deposited from very dilute solutions at temperature ranging between 80 and 120°C. Solvents like xylene, butyl acetate, isoamyl acetate, and diphenyl ether were used. Besides the already reported true and truncated lozenges, hexagonal crystals have been obtained with tendency to regularity as the temperature of crystallization increases. The melting point of hexagonal crystals is somewhat lower than that of lozenges. Their structure, as revealed by electron diffraction, is orthorhombic, similar to that of lozenges. Diamond‐shaped crystals etched with solvent under strictly controlled conditions display unexpected morphology. The peripheral region of the crystal of the sectors composing the crystals is characterized by a lower solubility and a lower density.
Solid state polymerization of methacrylamide and N‐arylmethacrylamides
Authors: Jäuger P. , Waight E. S. 
Published: April 2003

AbstractThe γ‐ray initiated solid state polymerization of methacrylamide at room temperature has been described and discussed in terms of reaction mechanisms previously applied to the radiation‐induced polymerization of acrylamide. Log (M0/M) increased, after a short initiation period, linearly with (time)2 up to conversions of about 20%. This was followed at higher conversions by a second linear region with a higher slope. The conversion rate (%/Mrad.) increased for intensities between 0.3 and 0.075 Mrad./hr., but it dropped unexpectedly at the lowest dose rates. Irradiated methacrylamide showed a post‐irradiation polymerization, the rate of which was influenced by the presence of air for reaction times longer than 200 hr. Among the solid N‐arylmethacrylamides, which were all less reactive than methacrylamide, some ortho‐substituted compounds (o‐Cl, o‐Br, o‐ethoxy) showed a relatively high reactivity. These results are discussed in connection with differences in hydrogen bonding found in the infrared spectra.
Specific diluent effects on polymer chain dimensions
Authors: Hoeve C. A. J. , O'Brien M. K. 
Published: April 2003

AbstractSpecific diluent effects on the unperturbed mean‐square end‐to‐end distance < r02 > may be determined in dilute solutions at their Θ‐points. Another method to determine these effects is described in this paper. It involves the measurement of the modulus of crosslinked polymers swollen with different diluents and interpretation of the results according to current rubber elasticity theory. As a result of the relatively high concentrations used in this method, combined with the introduction of crosslinks, specific diluent effects on chain dimensions are obtained, unobscured by excluded volume effects. The method is applied to polyethylene diluted with di‐2‐ethylhexyl azelate, α‐chloronaphthalene, n‐paraffin, tetralin, and n‐hexadecane. Within 10% the value of < r02 > in n‐hexadecane is equal to that in the other diluents used. In view of the similarity of the polyethylene molecule to those of n‐hexadecane and n‐paraffin this value must then also be equal to that for polyethylene in bulk. It may be concluded that, within experimental error, semi‐ordering effects in the melt are absent and that no specific diluent effects exist.
Examination of kinetics of graft copolymerization on preirradiated polymethyl methacrylate
Authors: Turska E. , Połowiński S. 
Published: April 2003

AbstractThe kinetics of graft copolymerization of vinyl acetate on polymethyl methacrylate has been investigated. Polymethyl methacrylate was preirradiated in the presence of air by γ‐rays, the polymer being used as the initiator of the polymerization in the one‐phase system. The rate of reaction for low conversion is proportional to the concentration of monomer raised to the power of 3/2 and to the concentration of initiator to the 1/2 power. The reaction satisfied the kinetic equation for ordinary addition polymerization if the decrease of the amount of the initiator during the process is taken into consideration. The activation energy of this process has been found. The quantity of the homopolymers produced in this reaction is negligible and need not be taken into account in rough calculations as far as kinetics are concerned.
On the additivity of osmotic properties of polyelectrolyte—salt solutions
Authors: Katchalsky A. , Alexandrowicz Z. 
Published: April 2003

AbstractThe simple additivity of osmotic pressure and ionic activity observed in polyelectrolyte—salt solutions is derived from a straightforward thermodynamic consideration. The basic assumption of this work is that the activity coefficient of the coions is practically uneffected by the presence of the largely screened polymeric ions.
Photosensitivity of dry‐heated polyacrylonitrile
Authors: Yoshino Tsuneo , Manabe Yasuo 
Published: April 2003

AbstractPolyacrylonitrile heated under appropriate conditions (time and temperature) in nitrogen or in vacuo was found to be photosensitive. On exposure to visible light, the visible light absorption of a heat‐treated polyacrylonitrile film shifts to longer wave length, and an ESR absorption is detected in heat‐treated powder. Solubility to acids changes on exposure to light, and acids of appropriate concentration dissolve only the unexposed portion of a polyacrylonitrile film and leave the exposed portion. The relation between these effects of light on dry‐heated polyacrylonitrile is discussed.
Radiation dosimetry in polyethylene with silicon solar cells
Authors: Salovey R. , Rosenzweig W. 
Published: April 2003

AbstractIrradiation dose rates and complete depth—dose curves in polyethylene have been directly determined with a silicon solar cell. In this manner, an average dose rate of 0.297 Mrad/sec. per incident μamp./cm.2 for 1 m.e.v. electrons in 120‐mil thick Marlex polyethylene was measured. The corresponding dose rate ascertained by ferrous sulfate dosimetry is 0.260 Mrad/sec. This difference is in the expected direction and may arise from differences in backscatter between polyethylene and silicon. The facility of the solar cell measurement and the complete definition of irradiation dose as a function of absorber thickness commend the device for general application in irradiation dosimetry.
Relative reactivity ratios for two new 2‐chloro‐1,3‐butadiene systems
Authors: Wich G. S. , Brodoway N. 
Published: April 2003

AbstractThe relative reactivity ratios in free‐radical, emulsion copolymerizations for the systems 2‐chloro‐1,3‐butadiene/methyl isopropenyl ketone and 2‐chloro‐1,3‐butadiene/methacrylic acid were found to be 3.6 and 0.1 and 2.68 and 0.15, respectively. Consequently, copolymers are formed substantially richer in 2‐chloro‐1,3‐butadiene units than the comonomer feed, have little alternation tendency, and do not form azeotropes. Distributions of monomer units in the copolymers are described.
Poly(4‐methyl pentene): X‐ray measurement of crystalline density and observation of a structural anomaly
Authors: Litt Morton 
Published: April 2003

AbstractThe unit cell of annealed poly(4‐methyl pentene) was measured by x‐rays; the unit cell is tetragonal with a = b = 18.50 ± 0.03 A. and c = 13.76 ± 0.07 A., which leads to a crystalline density of 0.832. This is lower than the density of the quenched polymers. Previous workers have postulated a 72 helix for the polymer. A reflection of 001 was observed consistently, which is forbidden for this helix. A superficial investigation indicates that the polymer crystallizes in a helical form but probably the side groups are displaced from a helical arrangement because of interference by neighboring side groups.
Nuclear magnetic resonance in solid polypyrrolidone
Authors: Filipovich G. 
Published: April 2003

AbstractNuclear magnetic resonance in solid poly‐2‐pyrrolidone has been studied over the temperature range 77–450°K. Experimental evidence concerning the differently ordered regions that contribute to the composite NMR curves has been obtained. Experimental techniques and results are described in detail. A detailed comparative interpretation of two‐component NMR curves as a function of temperature is offered in terms of motion in differently ordered regions. The width of the component corresponding to the crystalline regions was found to be independent of temperature over a certain range above that of liquid nitrogen; this is taken to indicate a rigid structure. At higher temperatures there is a gradual decrease in line width indicating increasing segmental molecular motion. The NMR line width representing amorphous regions was found not to change over approximately the same range of low temperatures; it then decreases faster with increasing temperature than that of the crystalline regions; it finally decreased sharply and became the narrow component above the glass transition temperature. The glass transition temperature in polypyrrolidone appears to decrease with increasing water content. Comparison of the temperature of glass transition of dry polypyrrolidone with those of other polyamides supports the observation that the temperature of this transition is lower, the smaller is the ratio of NH groups to methylene groups in a polyamide. Empirical second moment values at liquid nitrogen temperature and at room temperature, as well as an estimate of theoretical second moment for an assumed sheet model, are reported.
Interactions of low molecular weight compounds with solid polymers
Authors: Kryszewski Marian , Skorko Marta 
Published: April 2003

AbstractIn order to establish the kind of dispersion of low molecular weight compounds in solid polymers the absorption spectra of their solutions in liquid monomer and solid polymer were investigated. On this basis the oscillator strengths were calculated for solutions of the light stabilizers, 5‐chloro‐2‐hydroxybenzophenone phenyl salicylate, and 1‐naphthylamine in monomer and polymer. The change of oscillator strength is related to the change of dispersion character. Styrene and polystyrene were used as solvents. The hydroxybenzophenone and salicylate show molecular dispersion in the case of thermal polymerization, and are slightly incorporated into the chains during the initiated polymerization. Naphthylamine is incorporated into the chains in a higher degree. Besides it was stated that the oscillator strength is almost independent of conversion degree. If the incorporation of investigated substance into the chains takes place it occurs during the entire polymerization process.
Molecular configuration of polystyrene in benzene
Authors: Debye P. , Chu B. , Kaufmann H. 
Published: April 2003

AbstractThe particle scattering factor P(ϑ) with Gaussian statistics for polydispersed systems has been treated. For a polystyrene sample with a sharp molecular weight distribution (Mw/Mn < 1.02, Mw = 1.5 X 106), the measured angular dependence of scattered intensity indicates that the polymer coil does obey Gaussian statistics. This holds for a range of concentrations provided the variation of the constant representing the radius of gyration with concentration is adjusted.
Competing side reactions in the polymerization of α‐olefins by ziegler‐natta catalysts
Authors: Ketley A. D. , Moyer J. D. 
Published: April 2003

AbstractThe polymerization of 3‐methylbutene‐1 by TiCl3–Al(C2H5)3 catalysts in dilute solution above 80°C. yields a polymer which is contaminated with polyethylene. By using tagged aluminum alkyl, this polyethylene was shown to arise almost wholly by displacement of ethylene from the alkyl by the monomer. This side reaction was shown to be a general one in the polymerization of α‐olefins other than propylene at elevated temperatures. Analysis of the gas phase above the reaction showed also that some decomposition of the monomer occurs under these conditions.
Use of dimaleimides as accelerators for the radiation‐induced vulcanization of hydrocarbon polymers. Part II. Synthetic rubbers and saturated polymers
Authors: Miller S. M. , Spindler M. W. , Vale R. L. 
Published: April 2003

AbstractThe effect ofm‐phenylenedimaleimide on the rate of cross linking of synthetic rubbers, polyvinyl acetate, polyvinyl chloride, polyethylene, and other polymers, under the action of ionizing radiation is described. The dose reduction factor for equivalent degrees of crosslinking obtained with and without the maleimide varies from 10 to 25 for the synthetic rubber. Further evidence is given to show that maleimides sensitize the vulcanization of unsaturated polymers, principally by copolymerization, and certain saturated polymers containing labile atoms, by a transfer mechanism.
Infrared spectra and assignments for polyvinyl chloride and deuterated analogs
Authors: Krimm S. , Folt V. L. , Shipman J. J. , Berens A. R. 
Published: April 2003

AbstractDeuterated analogs of polyvinyl chloride (PVC) have been prepared and their infrared spectra analyzed as an aid to the more detailed assignment of bands in the spectrum of PVC. The following deuterated polymers were studied: PVC‐αd1, PVC‐βd1, PVC‐αβd2, and PVC‐d3. These, as well as PVC, were polymerized in urea‐complex, at −78°C., and at +50°C. in order to determine which bands are of crystalline origin and which of noncrystalline origin. Polarized spectra of oriented samples were obtained in each case to assist in the analysis. As a result of this study several of the previously uncertain assignments have been clarified. With the help of other studies on model chlorine‐containing compounds it has been possible to identify the various conformations present in the polymer and to associate these with isotactic and syndiotactic pair configurations in the chain. A method is suggested for determining the proportion of each type of pair configuration in PVC.
Study of entanglement of polymers in solution by viscosity measurements. II. Polymethyl methacrylate in various solvents
Authors: Maron Samuel H. , Chiu Thomas T. 
Published: April 2003

AbstractA study has been made of the flow behavior at 30°C. of solutions of three samples of polymethyl methacrylate in three solvents in both the Newtonian and non‐Newtonian regions. The concentration range covered was approximately 0–16% by weight. By application of the Ree‐Eyring theory it was found possible to represent the observed data in terms of two flow units, and to obtain from the parameters of the theory the effective hydrodynamic volume occupied by the polymer in solution, ευ2. Here υ2 is the volume fraction of the polymer and ε an effective volume factor. The volume factor, ε, was found to be dependent on both solvent and molecular weight only up to ca. υ2 = 0.04. Beyond υ2 = 0.04, ε is independent of solvent and is a function of molecular weight only. These observations indicate that chain entanglement in solution is not probable. Rather, the polymer chain curls on itself, and compacts to a small mass when the effective concentration ευ2 = 1 and the viscosity becomes infinite. The concentration at which this occurs, υ∞, is given by ∞ = 1/ε∞. The quantity ε∞ has been found to be a linear function of molecular weight, M. Further, the value of ε at υ2 = 0, ε0, has been found to be an exponential function of M, and to yield expressions relating intrinsic viscosity to molecular weight in good accord with published results.
Further NMR studies of polydimethylsiloxanes: Effects of radiation‐induced crosslinking
Authors: Huggins C. M. , St. Pierre L. E. , Bueche A. M. 
Published: April 2003

AbstractPrevious nuclear magnetic resonance measurements on a polymethylsiloxane gum (MW = 75,000) had been interpreted to indicate the presence of considerable segmental motion in both the amorphous and crystalline components at temperatures above the glass temperature. Further investigation again showed the NMR line to be completely narrowed just above the glass point indicating such motions must extend into the crystalline component. This work was extended by the measurement of NMR absorption line widths for temperatures of 80–300°K. on samples of the same gum subjected to gradually‐increased crosslinking by electron doses of 3–600 × 106 rep. Here, no change in the NMR properties of low temperature, rigid states were observed, but the room temperature line width progressively increased from 0.019 gauss to over 0.100 gauss peak‐to‐peak due to the increase in bulk viscosity of the liquid. The “first‐order” activation energy associated with the temperature‐dependent line narrowing decreased from 10 to 2 kcal./mole. The NMR data indicate that the primary effects of radiation‐induced crosslinking are to reduce the chain rotational energy by the creation of defects and to increase the short‐range viscosity by the lowering of translational freedom.
An improved ebullioscope for high polymers
Authors: Arnett Raymond L. , Smith Melvin E. , Buell Barry O. 
Published: April 2003

AbstractA description is given of an ebullioscope which was calibrated and found satisfactory for determining the number‐average molecular weight of several unbranched polyethylenes. It employs a benzene‐filled Menzies differential vapor pressure thermometer having a detection limit of 5 × 10‐6°C. In order to obtain a close approach to solvent—vapor and solution—vapor equilibria, the boiler design incorporates a means of preheating the liquid solvent returning from the condenser and a mechanical lift pump to extract liquid solution from the boiler. In addition, time stability of these equilibria is provided by insulation to reduce heat conduction, reflectors to exclude radiant energy, constant pressure control, and constant wall temperature. An analysis of the observed temperature fluctuations shows that these features result in thermometer noise which is lower by an order of magnitude than any heretofore reported. Full advantage from this improvement has not been realized in interrupted (3‐day) experimental runs which gave a standard deviation of 400 at the 10,000 molecular weight level. Indications are that full benefit of the reduced thermometer noise with severalfold further reduction in standard deviation, could be realized in uninterrupted runs.
Crystallization and melting behavior of polyacrylonitrile
Authors: Chiang R. 
Published: April 2003

AbstractDilatometric measurements have been carried out on the crystallization of poly‐acrylonitrile from propylene carbonate solutions at concentrations of 1.0, 4.2, and 8.4% and temperatures of 40, 70, 95, 104, and 108°C. Contrary to expectation, the volume of the solution actually increases upon crystallization, although the increase is extremely small (about 1% based on polymer). This small change in volume is consistent with the partial specific volume of polyacrylonitrile in solution and the specific volume of the polymer measured directly by a flotation method. Recent investigation by Holland, et al. revealed that polyacrylonitrile, upon crystallization from dilute solution, forms crystalline platelets resembling the single crystals observed in other polymers. It appears that the small change in volume on transformation from the dissolved state into the crystalline state is due to the closeness of the specific volumes in the two different states. These unusual density data of polyacrylonitrile resemble those of poly(methyl‐methacrylate), where isotactic, syndiotactic, and atactic polymers have about the same density. The fact that the difference in density of polyacrylonitrile is so small might well explain a number of related phenomena: the lack of abrupt volume change on melting, the absence of amorphous regions, the narrow range of the density values of different samples prepared by different methods, and the fact that crystallization conditions exert practically no effect on the density of the sample.
Effect of ions on the dielectric dispersion of ovalbumin solution
Authors: Takashima Shiro 
Published: April 2003

AbstractThe dielectric dispersion of ovalbumin solution was studied in the presence of various ions. It was found that ions such as tetraethylammonium, ammonium, Na, and K which are not bound to the protein had no effect on the dielectric increment or on the relaxation time. On the contrary, the addition of ions such as Cu, Ca, Mg, and H ions had a considerable effect on the dielectric increment as well as on the binding of the ions to the protein. These results indicate that ions do not affect the dielectric dispersion parameters of this protein unless they have specific interaction with the polar sites of the ovalbumin molecule. The electric polarization of protein solutions is discussed and it is suggested that the ion fluctuation process including the Maxwell‐Wagner effect is not necessarily the essential mechanism of dielectric polarization of isoelectric protein solutions.
Tracer techniques for the determination of monomer reactivity ratios. IV. Monomer reactivity ratios for styrene–isoprene copolymerization
Authors: Wiley Richard H. , Davis Burns 
Published: April 2003

AbstractThe ionization chamber‐vibrating reed electrometer assay technique has been improved in precision (±0.25% average deviation) and used to determine monomer reactivity ratios for the styrene—isoprene copolymerization. Values of r1 (styrene) = 0.50 (100°) and 0.54 (80°) and r2 = 1.92 (100°, 80°) have been obtained for the radical initiated copolymerization. For γ‐irradiation initiation at 22°, r1 = 0.66 and r2 = 1.88. For butyllithium initiation, r1 = 0.03 and r2 = 5.9. The difference in the radical and γ‐radiation initiation values is considered in terms of possible partial ionic character of the radiation initiation process and possible temperature dependence of the reactivity ratios (r1) over the 22–100°C. range. The latter indicates a difference in activation energy of 0.8 kcal./mole for the radical to styrene and radical to isoprene propagation steps.
Proton magnetic resonance in natural rubber: Comparison with dielectric measurements
Authors: Kusumoto Hazime , Gutowsky H. S. 
Published: April 2003

AbstractProton magnetic resonance studies have been made of cured natural rubber containing up to 31% combined sulfur. Line shapes and spin‐lattice relaxation times were observed at temperatures between —190 and 180°C. In the line shape studies, the main effect of the combined sulfur was upon the temperature at which the line width is narrowed by the molecular segmental motions. The temperature at the onset of the major line width narrowing increases from —50°C. for raw rubber to about 10°C. for 31% combined sulfur. A relation was found between the dependence upon sulfur content of the line width changes and the second‐order transition temperature. The proton spinlattice relaxation timeT1was measured for three cured samples in the temperature range above the motional narrowing region. TheT1vs. temperature curves agree qualitatively with the theory of Kubo and Tomita. The general features of theT1curves are consistent with a distribution of correlation times which broadens with increasing sulfur content. Energies of activation were computed from these results and they are compared with the dielectric relaxation data obtained previously. The effect of a distribution of correlation time is discussed.
Conductivity and viscosity measurements on sodium polyacrylates of different molecular weights
Authors: Packter A. 
Published: April 2003

AbstractCombined conductivity and viscosity measurements have been carried out on a series of sodium polyacrylate solutions of different molecular weights with viscosities varying from 1.1 to 40 c.p. Analysis of the measurements indicates that ionic mobilities in polyelectrolyte solutions are not affected by overall solution viscosity; i.e., the Walden rule is not applicable to such solutions.