bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneous nucleating agents for polypropylene crystallization
Authors: Beck H. N. 
Published: April 2003

AbstractA model nucleating agent for polypropylene crystallization is described. A series of compounds consisting mainly of organocarboxylic acid salts is evaluated as heterogeneous nucleating agent for polypropylene crystallization by measuring their effect upon the polymer supercooling. Sodium benzoate and basic aluminium dibenzoate were among the best nucleating agents found. The nucleating abilities of the various compounds are discussed in terms of their structural features.
Oscillating flow behavior of high‐density polyethylene melts
Authors: Myerholtz R. W. 
Published: April 2003

AbstractThe oscillating flow behavior of a variety of high‐density polyethylene and copolymer samples was studied in a constant displacement rate rheometer. At any plunger velocity, the period of the oscillations decreases linearly with melt depth, suggesting a resonance phenomenon. As plunger velocity is increased, the load waveform changes in a regular manner that indicates a progressive increases in the proportion of each cycle spent on the right‐hand branch of the flow curve. Little difference was found in the shear stress at which oscillating flow began for samples differing in molecular weight, molecular weight distribution, and manufacturing process. However, the shear rate at which oscillating flow begins depends, strongly on both molecular weight and distribution. Oscillating flow is shifted to higher shear rates by broadening distribution, reducing molecular weight, increasing temperature, or decreasing the L/D ratio of the capillary.
Estimation of kinetic parameters during Teflon degradation from linearized differential TGA traces
Authors: Reich Leo 
Published: April 2003

AbstractIn a recent communication,1 mathematical expressions were derived for obtaining kinetic parameters during polymer pyrolyses from linearized DTA traces. The approximate method developed is now extended to differential TGA traces in this paper and is applied to polytetrafluorethylene (Teflon). The results obtained are compared with those obtained from more elaborate procedures.
Molecular weight changes in irradiated polypropylene
Authors: Marans N. S. , Zapas L. J. 
Published: April 2003

AbstractWe have shown by two separate measurements that polypropylene when melted after irradiation undergoes crosslinking from the inception of irradiation. The first proof was an immediate increase in the solution viscosity of a narrow molecular weight fraction of polypropylene. The second proof was the marked change in melt‐flow properties on irradiation of a broad molecular weight distribution polypropylene. These findings tend to support one of the two currently held views on the action of radiation on polypropylene. In addition we have confirmed previous reports that melting after irradiation contributes to the overall crosslinking reaction.
Elastic behavior of concentrated solutions of acrylonitrile copolymers
Authors: Hayahara Takuro , Takao Seiji 
Published: April 2003

AbstractThe elastic behavior of concentrated solution of acrylonitrile copolymer was investigated by the capillary end correction method. The results were as follows. (1) The shear stress is proportional to recoverable shear strain in accordance with Hooke's law below critical concentration; above a critical concentration, however, the shear modulus depends on shear stress. (2) The log–log plots of zero shear modulus against polymer concentration and molecular weight fall on two straight lines with different slopes. The intersection of lines is considered to be the onset of elastically deformable entanglement network. We denote this inflection point as (Cc)e or (Mc)e. (3) The log–log plot of viscosity against polymer concentration does not show a change of slope at the critical concentration (Cc)e. (4) By the application of the kinetic theory of rubberlike elasticity to the pseudo‐network structure of concentrated polymer solution, in the range of Cc < C < (Cc)e or Mc < M < (Mc)e, the number of chain entanglement per molecule is kept one; moreover, in the range of C > (Cc)e, or M > (Mc)e, the number of chain entanglement increases to three.
Derivation and correction of polyethylene melt strength equation
Authors: Combs R. L. , Slonaker D. F. , Coover H. W. 
Published: April 2003

AbstractThe following equation for the determination of polyethylene melt strength (MS) has been derived:

where Δl is the length (inches) of extruded polymer cord required for 50% decrease in diameter of the cord, r0 is the radius (inches) of the molten polymer cord as it first emerges from the melt indexer die, and MF is melt flow rate in grams/10 min. The required measurements are made on the initially extruded 0.5‐in. portion of the polymer cord from a conventional melt indexer using the standard 0.0825‐in.‐diameter die and 2160‐g. load and a temperature of 230°C. This melt strength equation was derived by using the assumption that the melt strength can be expressed as melt viscosity at low shear rates. Melt strengths of polyethylenes having similar melt indices have been shown to have over a 37‐fold difference.
Ionic graft copolymerization. I. Homopolymerization of β‐propiolactone by sodium acetate catalyst
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro 
Published: April 2003

AbstractThe polymerization of β‐propiolactone (βPL) by sodium acetate catalyst has been investigated. The polymerization behavior with monomer purified with calcium chloride was found to be a little different from that previously reported for this monomer. That is, poly‐β‐propiolactone (PβPL) obtained from βPL dried with CaCl2 has a higher degree of polymerization than that obtained from conventionally treated βPL, and its infrared spectrum shows type II configuration, which differs from that reported in previous papers. Some chain transfer reaction is observed even for the polymerization of the CaCl2–dried βPL; however, this is less important in toluene. The electronegativity of the anion or cation in catalyst greatly influences the rate of polymerization.
Ionic graft copolymerization. III. Graft copolymerization of β‐propiolactone onto polyacrylonitrile containing diketene units
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractPolyacrylonitrile (PAN)–β‐propiolactone (βPL) graft copolymer was synthesized by means of the ionic polymerization of βPL in the presence of polyacrylonitrile containing diketene units by using basic catalysts. A graft copolymer was produced by the copolymerization of βPL with the lactone ring in the trunk polymer. In this graft copolymerization method, the grafting efficiency was low. However, grafting efficiency increased with the mole ratio of polymeric lactone to βPL; also higher molecular weight of PβPL favored higher grafting efficiency. The reactivity ratio of polymeric lactone to βPL was estimated to be in the range of 0.1–0.3.
Certain fine structure and thermal properties of benzhydrylated cotton cellulose
Authors: Stanonis D. J. , King Walter D. , Harbrink Pieter , Conrad Carl M. 
Published: April 2003

AbstractThe present paper describes the results of a preliminary study of certain physical and thermal properties of benzhydrylated cotton yarns. The 200‐yd. lengths of 7/2 yarn consisting of purified mercerized cellulose were reacted in a special reactor to various degrees of substitution from DS 0.31 to DS 1.22 with benzhydryl bromide in a mixture of equal volumes of 2,6‐lutidine and dimethylformamide. The products were examined for tensile strength at break, which decreased only slightly with substitution; ultimate elongation, which was relatively uniform at 60–70% of the control yarn; and tenacity, which decreased with substitution largely due to added weight. The energy of rupture remained relatively constant at about 50% above the control. Tensile stiffness decreased progressively with substitution to about 25% of the control. Density decreased 10–11% with substitution. Crystallinity of the cellulose largely disappeared with substitutions above DS 1, and the lattice of benzhydryl cellulose began to appear. Stiffness, elastic recovery and work recovery were measured on 5‐in. specimens of the yarn in an oven while they were subjected to repeated extension to about 1–2% and relaxed as the temperature was raised twice to 200°C. and lowered. During the heating phase of the first cycle the yarn underwent considerable heat adaptation. However, during the cooling phase and during both heating and cooling phases of the second cycle, the yarns showed generally favorable behavior. Attempts are made to interpret the results in terms of molecular modifications.
Membrane potentials of thin nitrocellulose membranes
Authors: Carnell Paul H. , McGunegle Daniel E. 
Published: April 2003

AbstractThe membrane potentials of thin (300–1300 A.) nitrocellulose (Parlodion) membranes have been investigated. Measurements were made in a Lucite cell by use of calomel electrodes with 0.05N KCl and 0.1N KCl. Variables having an influence on membrane structure, such as solvent polarity, temperature, and thickness, have been studied in relation to membrane potential. The range of potentials observed for Parlodion (2.1–9.2 mv.) is believed to be the result of differences in the orientation of the nitrocellulose molecules (and their accompanying electrochemically active carboxyl groups) in the membrane structure.
Radiation‐induced reactions with cellulose. II. The Trommsdorff effect: Dose and dose rate studies involving copolymerization with monomers in methanol
Authors: Dilli S. , Garnett J. L. 
Published: April 2003

AbstractThe radiation‐induced grafting to cellulose of styrene, methyl methacrylate, vinyl acetate, 2‐vinylpyridine, and 4‐vinylpyridine in methanol has been studied. All monomers exhibit appreciable grafting at room temperature in either vacuum or air for total doses up to 10 Mrad and at dose rates as high as 1.4 Mrad/hr. in a spent fuel or 60Co facility. The magnitude of the grafting depends upon both the total dose and dose rate. Under certain experimental conditions, the grafting experiences a maximum which has been attributed to the Trommsdorff effect. A novel mechanism involving charge‐transfer bond formation is proposed to account for the observed data in the grafting reactions.
Radiation‐induced reactions with cellulose. III. Kinetics of styrene copolymerization in methanol
Authors: Dilli S. , Garnett J. L. 
Published: April 2003

AbstractThe kinetics of the radiation‐induced grafting of styrene to cellulose in methanol have been studied in air at dose rates of 0.007, 0.014, and 0.078 Mrad/hr. in 60Co and spent fuel element facilities. The variables affecting rate of grafting include monomer concentration, radiation dose rate, and total dose. Grafting reaches a maximum at 60–70% by volume methanol in styrene. The results have been interpreted in terms of possible grafting mechanisms, including charge‐transfer intermediates; however, a complete mathematical treatment of the data is not possible at present because of the absence of appropriate swelling data for cellulose in mixtures of styrene and methanol. Poor grafting observed in solutions of up to 10% monomer is attributed to radical scavenging (predominantly from the solvent) by the monomer leading to the formation of scavenged products including homopolymer. Rate of grafting falls off for solutions above 80–90% monomer concentration and radical scavenging by monomer radicals is again postulated to account for the observed behavior.
Étude de l'étirage à froid des fibres de polymères synthétiques dans les agents organiques
Authors: Grellier M. R. 
Published: April 2003

AbstractThe cold drawing of synthetic polymers is generally carried out through necking at a short collar between the drawn part and the undrawn part of the fiber; if the drawing is carried out in certain organic liquids, the lengthening is realized through thousands of simultaneous necks which permit the fiber to be penetrated by a dye dissolved in the liquid. The stress–strain curves for the drawing in liquid show an important decrease in the force at the time the multiple necking are produced. This decrease is the result of an increase in the mobility of the macromolecular chains through the penetration of the organic liquid to the level of the shoulder of the necks. A morphological study has been carried out through the observation of cuts by optical microscopy, along with a utilization of the techniques of x‐ray diffraction, IR spectroscopy, and electron microscopy. It was found that the liquid penetrates t̀he fiber to the level of the necking via a rupture of the interchain bonds which takes place during the change of structural following the drawing. The bonds are maintained ruptured as long as the liquid is not squeezed out by the aligning of the chains; they reform later to produce a new highly crystalline structure.
Delayed yielding of epoxy resin under tension, compression, and flexure. I. Behavior under constant strain rate
Authors: Ishai Ori 
Published: April 2003

AbstractSeries of loading tests were carried out on epoxy resin specimens, at varying constant strain rates, under tension, compression, and flexure. The stress–strain relationship revealed a distinct yielding stage followed shortly by a post‐yielding region of decreasing load. In all cases, results indicate linearity between yield stress and log strain rate, in accordance with Eyring's theory of viscous flow. For specimens unloaded close to the yield point, photoelastic observations revealed a residual pattern parallel to the theoretical principal shear stresses. These results, supported by additional data from other works, indicate a viscoplastic deviatoric stress‐biased diffusional mechanism as the dominant factor in the yielding of an amorphous crosslinked epoxy system.
A generalized equation of state for polymers
Authors: Whitaker Herbert L. , Griskey Richard G. 
Published: April 2003

AbstractA simple, generalized equation of state has been developed that describes the pressure–volume–temperature behavior of both addition and condensation polymers. Use of the equation requires only that the polymer's glass temperature and density at 25°C. and one atmosphere be known. The equation applies to both amorphous and crystalline polymers for pressures up to 10,000 atm. It also appears to hold for copolymers. Polymer glass temperatures can also be estimated with the equation.
Fiber structures: A fresh look from metallography
Authors: Viswanathan A. 
Published: April 2003

AbstractThe parallel between fibers and metals is discussed in terms of their behavior upon heat treatment, crystallite size and orientation, and diffusion of atoms and molecules. It is pointed out that the degree of crystallinity employed to interpret the x‐ray diffraction patterns of fibers is not an important physical parameter. The need for critical study of the mechanism of the growth of primary and secondary walls is stressed for a better understanding of the physical properties of fibers. Reference is made to Hosemann's theory of paracrystals which will help to resolve the “open” problems in polymer physics.
A generalized flow theory
Authors: Lenk R. S. 
Published: April 2003

AbstractA generalized flow theory is put forward which is derived from a review of accepted types of stress–response curves. The theory is summarized in a single flow curve of universal shape from which all types of liquid flow can be interpreted. This “generalized flow curve” can be applied to polymer melts in particular, but there is no reason why it should not equally apply to solutions, dispersions, suspensions, emulsions, or pure liquids. The generalized flow curve is exactly analogous to the typical fully developed load–deformation curve which applies to tough plastics in the solid state. A molecular interpretation of the processes involved in producing the flow phenomena implicit in the various portions of the generalized flow curve is put forward. The evidence on which the theory is based is reviewed. Some fundamental implications are discussed.
Effect of carbon black on time dependence of the melt flow index
Authors: Schreiber H. P. , Rudin A. 
Published: April 2003

AbstractTime dependence in the melt indexing of polyolefins stabilized against thermally induced changes is well known, the prevalent effect being an increase in melt index toward a steady‐state value. The melt index of polyethylenes compounded with carbon black has been found to decrease, in some cases radically, although oxygen uptake data show no evidence of thermal instability. The melt index–time plot can be restored to its normal shape by adding excess quantities of a standard thioether antioxidant. Data are rationalized by assuming that polyethylene adsorbs on the available pigment surface, forming a crosslink network. The thioether antioxidant, however, may adsorb preferentially, thereby restoring the normal response of the polymer to forces resulting in its capillary extrusion. The results emphasize the contribution of chain orientation effects to the time dependence of melt index.
Infrared study of the cure of unsaturated polyester
Authors: Imai T. 
Published: April 2003

AbstractThe infrared spectra of unsaturated polyesters in process of cure have been taken of samples free from unreacted protion. Styrene and polyester fractions in the curing polyester films were assessed from comparison of the band intensities at 695 and 740 cm.−1. The styrene fraction in curing films was found to increase as cure proceeded, and the delayed curing was seen to be accompanied by a build‐up of films of lower styrene content. The differences between samples observed in the mechanical behavior were considered attributable for the most part to the difference in styrene content.
Radiation‐induced changes in the index of refraction, density, and dielectric constant of poly(methyl methacrylate)
Authors: Gardner Donald G. , Toosi Mohammad T. A. 
Published: April 2003

AbstractSamples of commercially prepared poly(methyl methacrylate) (Lucite) were irradiated with 13‐M.e.v. electrons in the dose range 0–11 Mrad, and the induced changes in the index of refraction, density, and dielectric constant were observed. An attempt is made to interrelate the observed changes theoretically.
Experimental determination of ultrasonic wave velocities in plastics as functions of temperature. IV. Shear velocities in common plastics
Authors: Asay James R. , Guenther Arthur H. 
Published: April 2003

AbstractThe temperature dependence of acoustic shear velocities are reported for Poly‐Penco nylon, type G Plexiglass [poly(methyl methacrylate)], TFE Teflon (tetrafluoroethylene), low‐ and high‐density polyethylene, Lexan (polycarbonate), and Delrin Acetal (nylon). Most of the data were obtained at a frequency of 1 Mc./sec. over the temperature range of 25–100°C. In addition, previously unreported longitudinal velocities to ∼125°C. are reported for Lexan and Delrin Acetal.
Radiation‐induced solid‐state polymerization in binary systems. V. Polymerization in binary systems containing long chain compounds
Authors: Kaetsu Isao , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractRadiation‐induced solid‐state polymerization in binary systems containing long‐chain compounds has been investigated. Butyl stearate–methyl methacrylate and stearyl alcohol–methyl methacrylate systems have been studied in detail. In these systems insource polymerization does not occur but a remarkable post‐polymerization takes place on warming after irradiation at low temperature. The limiting conversion characteristics of this post‐polymerization depend greatly on the nature and the concentration of the long‐chain compounds. The post‐polymerization is observed to be more marked in the butyl stearate–methyl methacrylate system than in the stearyl alcohol–methyl methacrylate system, and it increases with increasing concentration of the long‐chain component. An optimum warming rate and warming temperature exists for the maximum saturated conversion. Irradiation in air causes some decrease of conversion compared to irradiation in vacuo. The possible mechanism is that monomer diffuses into the crystals of the long‐chain compound after melting at the eutectic temperature. The polymerization may be initiated by trapped radicals of the long‐chain compound and carried out in the crystal of the long‐chain compound with a smaller possibility of termination. In binary systems containing long‐chain compounds, lowering of the melting point is slight, and the eutectic composition exists at the richer composition of monomer, so almost all the long‐chain substance remains as excess crystals, which are suitable for holding trapped radicals. The crystal lattices of long‐chain compounds may be softer than those of compounds of small molecular size. This fact is favorable for monomer diffusion. This explains why such a post‐polymerization takes place only in systems containing long‐chain molecules.
Radiation‐induced solid‐state polymerization of vinyl compounds in binary systems
Authors: Nishii Masanobu , Tsukamoto Hiroshi , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractThe radiation‐induced solid‐state polymerization in the binary systems such as acryl‐amide–methacrylamide and acrylamide–acenaphthylene was studied. The former system forms a solid solution, and the latter one forms a eutectic mixture. In the solid solution, the polymerization proceeds homogeneously and copolymer is formed, while in the eutectic mixture, it proceeds heterogeneously, forming only homopolymer. The post‐polymerization of the same binary systems was also studied. Linearity between the conversion and the logarithm of the post‐polymerization time was found for the various monomer compositions at various temperatures. This relationship satisfied the kinetic equation presented by Morawetz et al. for the post‐polymerization of acrylamide. The kinetics of the binary systems might be considered similarly to the single system, considering that the crystalline state of the system is changed by the monomer compositions.