bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ionic contribution to the complex dielectric constant of a polymer under dc bias
Authors: Uemura Shinsaku 
Published: April 2003

AbstractA diffusion equation for the distribution of ionic impurities in a polymer under a dc field has been solved analytically for the conditions that neither injection nor absorption of impurity ions takes place at either electrode and that the ions do not interact. By using the solution of the diffusion equation, an ionic contribution to the complex dielectric constant is calculated. The most important results are as follows. (1) At high temperatures and low frequencies, the dielectric loss factor of the polymer decreases exponentially with the time elapsed after the application of the dc bias. (2) The dielectric constant is not greatly affected by the bias. (3) The ionic contribution to the loss factor in the absence of the dc bias is represented as ϵi″ = 4πνDq2/ωkT, where ν is the density of mobile ions, D the diffusion coefficient, q the charge of an ion, ω the angular frequency, k the Boltzmann constant, and T the absolute temperature. (4) A method is presented for distinguishing between the apparent activation energy for diffusion and that for generation of mobile ions.
Kinetics of the 20°C phase transformation in polytetrafluoroethylene
Authors: Natarajan Raj T. , Davidson Theodore 
Published: April 2003

AbstractThe rate at which PTFE transforms from the triclinic to the hexagonal phase has been measured under isothermal conditions. Samples in a series of decreasing density and crystallinity show increased isothermal rates of transformation. Observed kinetic data are interpreted on the basis of a modified Avrami‐Johnson‐Mehl treatment. A model for the transformation in which planes of helix‐hand reversal propagate through the lattice is shown to fit the experimental results. The transformation rate is observed to be proportional to the total (001) surface area in the polytetrafluoroethylene specimens, suggesting that nucleation of the transformation takes place at grain boundaries.
Some morphological observations on polycaprolactam filament
Authors: Pasika W. M. , West A. C. , Thurston E. L. 
Published: April 2003

AbstractExamination of longitudinal, cross, and skew sections of extruded polycaprolactam filaments with the polarizing light microscope reveal morphological features not previously described. In cross‐sectional view, three distinct layers enclose a “homogeneous” central matrix. The outermost layer is characterized by large, birefringent, truncated cones extending upward from the surface. Associated with the cones and an entity in its own right is what appears to be a second layer of ultrafibrils. Below the latter is a fine‐structured layer of submicroscopic spherulites. A combination of the above features forms the transcrystalline region of stressed melts. Row nucleation is evident on the surface of the filaments.
Structure of fibers drawn from polyethylene single crystals
Authors: Petermann J. , Gleiter H. 
Published: April 2003

AbstractTransmission electron microscopy and electron diffraction were used to study the molecular structure of fibers drawn from polyethylene single crystals at 77, 293, and 383°K. The results suggest that the formation of the fibers occurs by a two‐step process. The first step is the breaking off of single blocks of folded chains from the single crystals so that a “string‐of‐pearls” structure is obtained. If the temperature is sufficiently high this process is followed by the thermally activated rearrangement of the molecules in the drawn fibers so that a “bamboo” structure results.
Light‐scattering method for investigation of the kinetics of crystallization of spherulites
Authors: Van Antwerpen F. , Van Krevelen D. W. 
Published: April 2003

AbstractA description is given of an apparatus for the continuous recording during crystallization of the spherulite radius, in the range of one half micron to a few microns, by scanning the Hv scattering pattern. At the same time the apparatus measures the change in intensity of the transmitted depolarized light, which is a measure of the overall rate of crystallization. The theoretical aspects of this measuring procedure are briefly discussed on the basis of light scattering by perfect and imperfect spherulites.
Fractography of a phenol—formaldehyde polymer
Authors: Nelson B. E. , Turner D. T. 
Published: April 2003

AbstractSamples of a phenol‐formaldehyde polymer with a deliberately introduced flaw were fractured in tension. The appearance of the fracture surface near the flaw suggested the disruption of particles pre‐existing in the polymer. At a greater distance from the flaw, a featureless surface was observed which was succeeded by one showing interference colors. At still greater distances, linear features were observed to be lying in the direction of crack propagation which, in most areas, were regular and evenly spaced. There were indications that these features were formed by the curling of a surface film. The above observations are interpreted as providing evidence that tensile fracture is accompanied by plastic defórmation at the fracture surface.
The thermal stabilization of poly(vinyl chloride) by allyl xanthate substitution
Authors: Nichols J. Dudley 
Published: April 2003

AbstractThe reaction of PVC with potassium allyl xanthate in DMF is discussed. Thermogravimetric analysis and differential scanning of calorimetry were used to evaluate the thermal stability. The allyl xanthate‐modified PVC (AX‐PVC) was shown to be significantly more thermally stable than the unmodified PVC homopolymer. The AX‐PVC is completely crosslinked at temperatures > 180°C. It was found that dibutyltin di‐2‐ethylhexanoate, a commercial PVC stabilizer, does not produce the same effect on the thermal stability of the AX‐PVC as it did on the unmodified PVC homopolymer.
Ring‐opening polymerizations of cyclic olefins
Authors: Hein Paul R. 
Published: April 2003

AbstractA ziegler‐type catalyst system consisting of tungsten hexachloride and alkyl or aryl tin compounds was found to polymerize cyclopentene and other cyclic olefins through a ring‐opening mechanism. This catalyst system also polymerized α‐olefins such as ethylene and 1‐octene. An attempt was made to copolymerize cyclopentene and ethylene. Other catalyst systems were also employed for ring‐opening polymerizations with limited success.
Universal calibration in GPC: A new approach for the calculation of molecular weights
Authors: Ambler M. R. 
Published: April 2003

AbstractA method has been developed for determining simultaneously the molecular weight of a broad‐distribution polymer and the Mark‐Houwink coefficients for that polymer type by using only GPC and intrinsic viscosity data. Standardized samples of poly(vinyl chloride), polystyrene, polybutadiene, and an experimental cycloolefin polymer were analyzed by this method. Shear‐corrected intrinsic viscosities were used in all cases because of the high molecular weights involved. Molecular weight data for all samples were found to be in good agreement with molecular weight data obtained by membrane osmometry and from other GPC techniques. The proposed technique provides a means for calculating the molecular weight of a single polymer sample through universal calibration of GPC without knowledge of the Mark‐Houwink coefficients for that polymer type.
Crosslinked polymers containing adamantane groups
Authors: Burreson B. J. , Levine H. H. 
Published: April 2003

AbstractDiglycidyl ethers of 1,3‐bis‐(p‐hydroxyphenyl)adamantane (BHPA) and 3,3'‐bis‐(p‐hydroxyphenyl)‐1,1'‐biadamantane (BHPBA) were prepared and condensed with m‐phenylenediamine and methyl tetrahydrophthalic anhydride to give polymers with good high temperature mechanical properties and good oxidative stability. These bisphenols were also condensed with formaldehyde to give phenolic resins containing adamantane moieties.
Stereoregulation in the radical polymerization of vinyl esters
Authors: Nozakura Shun‐Ichi , Sumi Masao , Uoi Michitake , Okamoto Takehiko , Murahashi Shunsuke 
Published: April 2003

AbstractTo determine favorable conditions for preparation of syndiotactic polymers, various factors which influence the stereoregulation of vinyl esters were studied. In bulk polymerizations, vinyl esters having bulky substituents or polar substituents were found most suitable for the syndiotactic polymerization. Tri‐n‐butylborane and azobisisobutylonitrile showed some difference in stereoregulation, the magnitude of the difference being dependent on the type of vinyl ester used. Solvents were found to have a significant effect on stereoregulation. Some gave higher syndiotacticity than bulk and some gave lower syndiotacticity.
Preparation and properties of aromatic poly(amide–benzothiadiazine dioxides)
Authors: Imai Yoshio , Koga Hiroshi 
Published: April 2003

AbstractNew thermostable poly(amide–benzothiadiazine dioxides) of high molecular weights have been prepared by the two‐step cyclopolycondensation of diaminobenzenesulfonamides and aromatic bisacyl chlorides. In the first step, the low‐temperature solution polymerization technique afforded open‐chain polyamides (I) having high molecular weights. In the second step, the polymeric precursors (I) underwent chemical cyclodehydration in the presence of organic basic catalysts at 160°C to give poly(amide–benzothiadiazine dioxides) (II), whereas thermal cyclodehydration gave unsatisfactory results. Not only the open‐chain polymers (I) but also the cyclized polymers (II) were soluble in polar solvents, such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone; tough films were cast from these solutions. Thermogravimetric analyses indicated that the cyclized polymers (II) began to decompose at 450–470°C under nitrogen or in air. It is interesting to note that both polymers I and II exhibited self‐extinguishing properties against free flame. The cyclodehydration of model compounds was also investigated.
Maleimide polymers. I. A polymeric color reaction
Authors: Haas Howard C. , MacDonald Ruby L. 
Published: April 2003

AbstractCertain copolymers of maleimide and N‐substituted maleimides yield brilliant colors when treated with sufficiently strong basic reagents under nonhydrolytic conditions. For color generation, the copolymer must be capable of HX elimination. The chromophores which account for color probably result from the ionization of acidic protons in structures involving one or more double bonds conjugated with imide carbonyl. The analogy to the color reactions of aconitylanil is pointed out. Spectra covering the range of 330–700 mμ are presented for a number of copolymer–amine color‐generating systems. The colors produced in base with radical‐initiated polymaleimide and imidazole‐initiated poly‐N‐alkylmaleimides as well as the absence of color with anionic polymaleimide and radical poly‐N‐alkylmaleimides are discussed in light of what is known about their polymerization kinetics and mechanisms. Corresponding maleic anhydride copolymer systems are mentioned.
Cyclic diamides. II. Syntheses and polymerizations of perhydro‐1,5‐diazocine‐2,4‐dione and its derivatives
Authors: Iwakura Yoshio , Uno Keikichi , Haga Kazuo , Nakamura Koutarou 
Published: April 2003

AbstractOne isomer, perhydro‐1,5‐diazocine‐2,4‐dione, was obtained exclusively by the double Beckmann‐rearrangement reactions of cyclohexane‐1,3‐dione dioxime. It is suggested that the other possible isomer was decomposed by a transannular reaction. Perhydro‐1,5‐diazocine‐2,4‐dione was polymerized in the solid state in the presence of water vapor and produced polytrimethylenemalonamide. Further, this monomer was polymerized in the molten state without water. 7‐Methyl‐ and 7,7‐dimethyl‐perhydro‐1,5‐diazocine‐2,4‐dione were prepared, and the latter was polymerized in molten state. Differential thermal analyses of the monomer and x‐ray diffraction measurements of the polymers were carried out.
Applications of ESCA to polymer chemistry. III. Structures and bonding in homopolymers of ethylene and the fluoroethylenes and determination of the compositions of fluoro copolymers
Authors: Clark D. T. , Feast W. J. , Kilcast D. , Musgrave W. K. R. 
Published: April 2003

AbstractMolecular core binding energies have been measured by ESCA for the homopolymers of ethylene and the fluoroethylenes. The data are interpreted in terms of semiempirical all‐valence electron SCF MO calculations in the CNDO/2 formalism, in conjunction with the charge potential model. The results are used as a basis for interpreting the measured core binding energies of some Viton and Kel F type polymers. The routine application of ESCA to the determination of copolymer compositions is described.
Chromocene‐based catalysts for ethylene polymerization: Kinetic parameters
Authors: Karol Frederick J. , Brown Gary L. , Davison James M. 
Published: April 2003

AbstractThe chromocene catalyst for ethylene polymerization shows a high response to hydrogen which leads directly to highly saturated polyethylenes containing methyl groups as the major terminal functionality in the polymers. At a polymerization temperature of 90°C the ratio of termination rate constants for hydrogen (kH) and ethylene (kM) is kH/kM = 3.60 × 103. The ratio of kH to the chain propagation constant (kp) is kH/kp = 4.65 × 10−1 A simple relation that can be derived from polymerization kinetics and the Quackenbos equation exists between melt index and hydrogen–ethylene ratio. A deuterium isotope effect (kH/kD) = 1.2 was calculated for the termination reaction. The overall polymerization process has an apparent activation energy of 10.1 kcal/mole. Oxygen addition studies show catalyst activity is proportional to initial divalent chromium content.
Block copolymerization. VIII. Anionic polymerization of α‐pyrrolidone by polystyrene initiator
Authors: Yamashita Yuya , Murase Yasuo , Ito Koichi 
Published: April 2003

AbstractPolystyrene with N‐acyl pyrrolidone groups at both ends was prepared by radical polymerization with 4,4′‐azobis(pyrrolidone 4‐cyanovalerate). With this polystyrene as the initiator, the anionic polymerization of α‐pyrrolidone was carried out, to give the well‐defined ABA‐type block copolymers of α‐pyrrolidone and styrene. The obtained copolymers were characterized by their composition, reduced viscosity, and initiation efficiency. Initiation efficiency was sufficiently high, and the stepwise propagation process was verified so far as the polymerization time was not so long. The results of the polymerization in a high‐vacuum system were compared with those in a low‐vacuum system, and some differences were observed owing to the effect of water.
Polymerization of mixtures of alkyl methacrylates or alkyl acrylates with 4‐methyl‐1‐pentene by Ziegler‐Natta catalyst
Authors: Chiellini Emo , Nocci Roberto 
Published: April 2003

AbstractMixtures of methyl methacrylate (MMA) and 4‐methyl‐1‐pentene (4MP)(molar ratio MMA/4MP = 3–0.1) have been subjected to polymerization by VOCl3/Al(C2H5)3. The amorphous polymeric products, extractable with boiling methanol up to 75%, consist mainly of MMA monomeric units (∼80%). The composition of the product was almost independent of the starting MMA/4MP ratio. Comparison of these results with thoseof homopolymerization experiments shows that the presence of MMA drastically reduces the polymerization rate of 4MP. Moreover, 4MP is polymerized with rather low stereospecificity in the presence of MMA. Fractionation by solvent extraction of the unchanged polymeric products as well as of hydrolyzed samples seems to exclude the formation of random copolymers, suggesting to us that the polymerization of the two monomers takes place by different mechanisms. On taking into account these data and analogous data obtained with 4MP and alkyl acrylates or tert‐butyl methacrylate, is it suggested that, contrary to what has previously been proposed, the MMA polymerization by Ziegler‐Natta catalysts does not take place at the same centers which polymerize 4MP; moreover a coordinated anionic mechanism for MMA polymerization does not seem to be very probable.
Nitrogen‐containing organozinc and organoaluminum as catalyst for stereospecific polymerization of propylene oxide
Authors: Oguni Nobuki , Tani Hisaya 
Published: April 2003

AbstractCatalytic activities of the reaction products of diethylzinc or triethylaluminum with primary amines in the polymerization of propylene oxide were studied. Generally, organozinc compounds give higher ratio of the crystalline to the amorphous polymer than the organoaluminums. In the reactions of organometallic compounds with primary amines, Et2AlNPhAlEt2, Et2AlN‐t‐BuAlEt2, EtZnNH‐t‐Bu, and EtZn‐t‐BuZnEt were isolated in crystalline state. EtZnN‐t‐BuZnEt proved to be an excellent catalyst for the stereospecific polymerization of propylene oxide and forms coordination complexes with some electron donors such as dioxane, pyridine, epichlorohydrin and propylene oxide. The propylene oxide complex is unstable in solution and decomposes at temperatures above room temperature to give poly(propylene oxide), while the pyridine complex has no catalytic activity. Therefore, it is concluded that the polymerization of propylene oxide with this catalyst proceeds through the coordination of propylene oxide to the zinc atom of the catalyst.
Fortran IV programs for the penultimate copolymerization model
Authors: Pittman Charles U. , Rounsefell Thane D. 
Published: April 2003

AbstractThree programs have been written for calculations involving use of the penultimate copolymerization model. The first computes the penultimate reactivity ratios from composition‐conversion data, without constraints, at any conversion. A nonlinear leastsquares technique using Marquardt's algorithm is employed. The second program computes the four optimum starting monomer feed ratios,M10/M20which should be used by the experimenter from the penultimate reactivity ratios. These optimum feed ratios are obtained by choosing the conditions necessary to minimize the determinant of the variance‐covariance matrix. The input for the first program includes estimates of known values of the penultimate reactivity ratios. By using these two programs sequentially the experimenter has an optimized experimental approach toward evaluating penultimate reactivity ratios at any conversion. Finally, a program has been provided to calculate composition–conversion data, given penultimate reactivity ratios.
Thermal degradation of polybenzyl
Authors: Ellis Bryan , White P. G. 
Published: April 2003

AbstractPolybenzyl has been synthesized from the benzyl compounds, chloride, methyl ether, and isopropyl ether by using stannic chloride as the Friedel‐Crafts catalyst. The detailed structures of these polybenzyls have been determined by use of methods including elemental analysis, molecular weight determination, and infrared, ultraviolet/visible, and NMR spectra. The structure of these polybenzyls is globular with a high degree of branching. Thermal degradation was studied by using DTA and stepwise and isothermal degradation with analysis of both the volatile fraction and the residue. The activation energy for scissions was determined from changes in the molecular weight of the sample with time at a range of degradation temperatures of 340–440°C. The composition of the volatile fraction changed with both temperature and time of degradation. Thermal scission is directed to internal units and depends on the presence of weak links such as substituted anthracene units.
Peroxidation of caprolactam and its effect on equilibrium polymerization
Authors: Dege G. J. , Reimschuessel H. K. 
Published: April 2003

AbstractThe peroxidation of caprolactam has been studied at 84°C, 100°C and 120°C. The decomposition of the initially formed ε‐caprolactam hydroperoxide was found to be catalyzed by adipic acid monoamide which is formed by hydrolysis of adipimide. This imide results from the decomposition of the hydroperoxide and was found to act as oxidation inhibitor. The molecular weights of the polyamides obtained by polymerizing the peroxidized caprolactam were found to decrease as the extent of peroxidation and thus the concentration of adipic acid monoamide and other decomposition products increased. In all of these polyamides the concentration of acidic functions was appreciably higher than that of the titratable amino endgroups.
Formation and cure of novolacs: NMR study of transient molecules
Authors: Kopf P. W. , Wagner E. R. 
Published: April 2003

AbstractHigh‐resolution magnetic resonance spectroscopy has been used to investigate three areas of novolac resin chemistry: first, the lifetimes of glycol species in formalin under acid and base conditions and the reactivity of methylene glycol towards alcohols; second, the in situ identification of novolac resin intermediates; third, the novolac–hexamethylenetetramine cure mechanisms. It is shown that the mean lifetime of a given glycol species is an order of magnitude shorter under basic conditions than under an acid of equal normality. The ratio of the equilibrium constants for the addition of methylene glycol to methanol, benzyl alcohol, and phenol was measured as 70:20:1. New reactive intermediates were discovered while monitoring the reaction of phenol and formalin. The reactions of various phenols with hexamethylenetetramine were studied, and short‐lived benzoxazines were detected at 100–120°C whenever ortho hydrogen was available on the phenolic nucleus. The NMR peak assignments in the reaction sequence: benzoxazine, dibenzylamine, tribenzylamine, diphenylmethane are presented. Spectra of the very elusive p‐benzylamines of 2,6‐xylenol were recorded at 100–155°C. At 170°C, the lifetimes of these p‐benzylamines are too short to afford proton resonance spectra. No evidence of hexahydrotriazine or (CH2 = N‐CH2)3N type structures was found in 100 MHz NMR spectra of reaction mixtures of a phenol and hexamethylene‐tetramine.
13C nuclear magnetic resonance spectra of polyacrylates and their model compounds
Authors: Matsuzaki Kei , Kanai Taiichi , Kawamura Tokiji , Matsumoto Susumu , Uryu Toshiyuki 
Published: April 2003

Abstract13C nuclear magnetic resonance spectra (13C‐NMR) of poly(methyl acrylates) and poly(isopropyl acrylates) of various tacticities were measured at 25.1 MHz and analyzed. 13C‐NMR spectra of model compounds for poly(methyl acrylate), poly(acrylic acid), and poly(sodium acrylate) were also determined. The spectra of the polymers were generally complicated owing to the splittings corresponding to triad, tetrad, or pentad placements, and the assignment for each peak was difficult. Groups of peaks were analyzed by triad or tetrad placements by assuming Bernoullian or first‐order Markovian statistics.
Viscosity studies of polyethylene in a cosolvent mixture composed of two nonsolvents
Authors: Das Nita , Palit S. R. 
Published: April 2003

AbstractPolyethylene, normally soluble at an elevated temperature in some single solvents, is found to be soluble in the following binary mixtures of nonsolvents at a much lower temperature, (often in the vicinity of room temperature): xylene–carbon disulfide, cyclohexane–carbon disulfide, cyclohexane–trichloroethylene, and cyclohexane–cyclohexanone. The fractionated polymer samples show a maximum in [η] values at the optimum solvent compositions corresponding to a minimum in cloud temperature Te. The results are discussed with respect to the current theories on solubility. The optimum solvent composition agrees with the prediction of a newly developed theoretical equation in two of the above four mixtures.