bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural characterization of vulcanizates. XII. Efficient vulcanization using a sulfenamide–thiuram disulfide accelerator system
Authors: Campbell D. S. 
Published: April 2003

AbstractVulcanizates obtained from the sulfur vulcanization of natural rubber using a combination of the accelerators N‐cyclohexylbenzothiazole‐2‐sulfenamide (CBS) and tetramethylthiuram disulfide (TMTD) have been analyzed in terms of the numbers of poly‐, di‐, and monosulfide crosslinks, network‐bound accelerator residues, and cyclic sulfide chain modifications as a function of cure time. The vulcanization system produced mainly monosulfide crosslinks at optimum cure, although there were differences in detail between this mixed system and a previously reported efficient sulfur vulcanization (EV) system using a high ratio of CBS to sulfur.
The determination of adjacent oxypropylene–oxyethylene units in propylene oxide–ethylene oxide adducts by infrared spectroscopy
Authors: Gibson U. H. , Quick Q. 
Published: April 2003

AbstractA study of several base‐catalyzed propylene oxide—ethylene oxide adducts of glycerin and certain model compounds has shown that an infrared absorption band at 10.30 μ can be associated with a structural entity represented by an oxyethylene unit attached to an oxypropylene unit at the secondary position. Coupled with other information such as total oxyethylene content and primary hydroxyl content, this finding has proved most useful in differentiating average molecular structure for commercial polyether polyols used in the manufacture of polyurethanes.
Effect of concentration of atactic polypropylene on its rate of autoxidation
Authors: Jadrnicek B. R. , Stivala S. S. , Reich Leo 
Published: April 2003

AbstractA general scheme previously reported for the autoxidation of polyolefins is further substantiated by results obtained for the uncatalyzed and catalyzed autoxidation of various concentrations of atactic polypropylene (APP) (by admixture with polyisobutylene) under various experimental conditions. Thus, rates of maximum carbonyl formation were measured as a function of APP concentration at 120°C, oxygen concentrations ranging from 0.5%–100% by volume and cobaltic acetylacetonate catalyst concentrations (3 and 17) × 10−7 mole/7.5 mg sample. Good agreement was found between experimentally observed and theoretical dependencies of the maximum carbonyl formation rate on APP concentration derived from the combined reaction scheme.
X‐ray low‐angle scattering from oriented poly(ethylene terephthalate) films
Authors: Heffelfinger C. J. , Lippert E. L. 
Published: April 2003

AbstractLow‐angle x‐ray scattering data are used to deduce the morphology of oriented polymeric films. Generally, the structural models proposed to explain these patterns have been extrapolations of observations made from solution‐grown polymer single crystals or from highly crystalline bulk polymers. These models and explanations may not be applicable broadly to oriented systems having only modest amounts of crystallinity or to those generated from precursor states that are grossly different. Poly(ethylene terephthalate) (PET) was chosen as a model polymer system for study. A systematic series of uniaxially and biaxially deformed films were produced from this polymer, made from the initially glassy or crystalline states. The low‐angle x‐ray scattering patterns generated from these films were studied as a function of (a) the sequence of deformation, (b) the precursor structure, (c) molecular orientation, and (d) the direction of observation. Optical diffraction and model structures were used to aid in the interpretation of the morphology produced. At least three different‐sized domains are developed upon deformation, ranging from that of the unit cell (about 10 Å) to large laminar domains of average size 2,000 Å × 10,000 Å. This structure is shown to be substantially different from that developed in an oriented polyethylene film.
Effect of wavelength region on photo‐induced graft copolymerization onto cellulose
Authors: Kubota Hitoshi , Ogiwara Yoshitaka 
Published: April 2003

AbstractThe effect of wavelength region of ultraviolet light was examined on the unsensitized photo‐induced graft copolymerization of methyl methacrylate onto cellulose. When the quartz tube system was compared to the glass tube system, there was no induction period of copolymerization, the rate of reaction was a little larger, the homopolymerization of methyl methacrylate was increased causing interference with graft copolymerization, and the depolymerization of grafts and the scission reaction of cellulose chains occurred easily. The number of grafts was hardly improved by varying the reaction conditions, and the copolymers obtained generally exhibited low per cent grafting and contained grafts with lower degree of polymerization.
Calculation of molecular weight for polymers produced in continuous‐flow stirred reactors
Authors: Cozewith Charles 
Published: April 2003

AbstractFor addition polymers produced in continuous flow stirred tank reactors, a method is described for deriving equations for the degree of polymerization directly from the equations for the polymerization kinetics. Through use of this technique, relationships are obtained for calculating the number and weight average degree of polymerization in both homo‐ and copolymerization.
Iodine treatment of nylon: Effect on metal plating of the polymer
Authors: Abu‐Isa Ismat A. 
Published: April 2003

AbstractThe iodine treatment of nylon surfaces consist essentially of dipping the nylon in an iodine—potassium iodide solution and quickly rinsing the absorbed iodine out of nylon surfaces using glycol—water—thiosulfate as a wash solution. The treatment was found to profoundly affect the adhesion between the nylon and an electrolessly deposited metal on its surface. The adhesion changes from no adhesion for an untreated nylon surface to a maximum of 28 lb/in. for a treated sample. The adhesion is dependent mainly on the nature of the nylon surface (crystallinity, molecular weight, etc.), the duration of the iodine treatment, and the nature and conditions of the wash solution. Electron microscope pictures of the nylon surface after the iodine treatment show a shallow etching pattern, and therefore mechanical keying between the metal and the polymer is not a probable factor of importance. Under certain experimental conditions, the iodine treatment changes the crystallinity from the α‐form predominant in the nylon before treating the sample to the γ‐form. It also decreases the overall crystallinity of the surface, softens the polymer, and improves its water wettability. All the above changes enhance a more intimate interaction between the deposited metal and the polymer.
Physicochemical criteria for reverse osmosis separation of alcohols, phenols, and monocarboxylic acid in aqueous solutions using porous cellulose acetate membranes
Authors: Matsuura Takeshi , Sourirajan S. 
Published: April 2003

AbstractReverse osmosis data of 32 different alcohols and phenols and 22 different monocarboxylic acids in aqueous solutions in the concentration range 0.0001 to 0.007M (∼100 ppm in most cases) have been studied using porous cellulose acetate membranes at 250 psig. Solute separation data for alcohols and phenols are correlated with Δνs (shift in the OH band maximum in the IR spectra), and those for the monocarboxylic acids are correlated with Ka (dissociation constant) and the degree of dissociation of the molecule. Solute separation decreases with increase in Δνs for alcohols and phenols. The solute separation‐versus‐Ka correlation for acids passes through a minimum, and solute separation always increases with increase in the degree of dissociation. The separation data are also correlated with Taft and Hammett numbers which represent the effect of the substituent group on the polar effect of the molecule. The product rate data show a general tendency to decrease with decrease in solute separation in all cases. These results show that, with respect to the systems considered, solute separation in reverse osmosis is governed by the hydrogen bonding ability of the organic molecule when it is essentially undissociated and by electrostatic repulsion of ions when the molecule is partially or completely dissociated. Thus, data on Δνs for alcohols and phenols, and those on Ka and degree of dissociation for monocarboxylic acids, constitute precise physicochemical criteria for reverse osmosis separation of the above solutes in aqueous solutions using porous cellulose acetate membranes.
The graft copolymerization of styrene and lignin. I. Hydrochloric acid lignin
Authors: Phillips R. B. , Brown W. , Stannett V. T. 
Published: April 2003

AbstractThe effects of methylation of phenolic hydroxyl groups and addition of solvent on the radiation and chemically initiated graft copolymerization of styrene and hydrochloric acid softwood lignin were studied. In the radiation‐induced experiments, methylation is found to increase the maximum per cent graft obtainable two or threefold, while methanol addition may increase the value tenfold. Chemically initiated experiments indicate that the main effect of methanol addition is to increase the accessibility of the lignin particles. A mechanism of graft copolymerization of polystyrene and lignin is proposed which requires the reaction to proceed primarily by chain transfer of a polystyrene chain radical to lignin and the subsequent reinitiation of polymerization (i.e., initiation of graft copolymerization) by the lignin radical. The grafting of lignin modifications is then dependent on the type of radical formation (i.e., phenoxy or benzylic) most favored, as well as the usual accessibility considerations.
Properties of hydroxyl‐terminated polybutadiene‐urethane systems
Authors: Consaga John P. , French David M. 
Published: April 2003

AbstractThe properties of liquid hydroxyl‐terminated polybutadiene (HTPB) stocks crosslinked with isocyanates of different functionalities were intensively investigated. The stocks were modified by inclusion of small proportions of various low molecular weight diols to increase the urethane concentration. The following studies were carried out: (1) the system functionality was varied at a low and relatively constant urethane concentration; (2) the system functionality was varied with the urethane concentration constant but at a higher level; (3) at a constant crosslink density, the urethane concentration was varied by adding low molecular weight diols; and (4) the structure of the diols used in the previous experiments was varied.A correlation between the per cent functional groups reacted, the average functionality of the system, and the mechanical properties of simple HTPB stocks was attained. Furthermore, a correlation was found between mechanical properties and urethane concentration at constant crosslink density. The properties of the stocks could be varied enormously by addition of low molecular weight diols in relatively small proportions by weight. The structure and concentrations of these diols caused significant variations in the elongation‐at‐break and tensile strength values.
Aqueous degradation of polyimides
Authors: DeIasi R. , Russell J. 
Published: April 2003

AbstractThe effect of an aqueous environment on the tensile properties of Kapton polyimide film has been investigated. Immersion of specimens in distilled water at 25° to 100°C for time periods ranging from one hour to several hundred hours resulted in a decrease in the ultimate tensile strength of the polymer from 23 ksi to approximately 14 ksi, and a corresponding decrease in elongation to failure from 38% to approximately 5%. The kinetics of this decrease in mechanical properties are second order and yield an activation energy of approximately 15.6 kcal/mole. The reaction is slightly dependent on pH in the range 2.0 to 12.0, but is highly dependent on the pH in the range 0.4 to 2.0. The decrease in mechanical properties at pH 2.0 to 6.0 appears to be due to hydrolysis of either uncyclized amic acid linkages or diamide functional groups present in the polyimide, whereas that at pH below 2.0 is probably the result of hydrolysis of both imide and amide bonds. Prolonged reflux of the polyimide in water resulted in the extraction of a water‐soluble, amide‐containing material.
Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I
Authors: Oraby W. , Hopfenberg H. B. , Stannett V. 
Published: April 2003

AbstractThe effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.
On creep test loading for soft polymers
Authors: Kobayashi Akira , Ohtani Nobuo , Ino Shuji 
Published: April 2003

AbstractThe dead‐weight loading speed in the creep test for soft polymers was investigated. The optimum dead‐weight loading speed can be determined so as to assure instantaneous elastic deformation and, at the same time, also avoid dynamic effects. It is found that small dynamic effects are inevitable for soft polymers such as polypropylene even at optimum speed. The experimentally determined optimum dead‐weight loading speed for polypropylene was 300 mm/min for 30 kg dead‐weight at 16°C.
The pyrolysis of wool and the action of flame retardants
Authors: Ingham Peter E. 
Published: April 2003

AbstractThe thermal degradation of untreated wool and wool treated with a number of flame retardants has been studied in a variety of atmospheres using thermogravimetric analysis and pyrolysis–gas chromatography. The major products of pyrolysis have been identified and their amounts determined. Gas evolution curves have been determined for the main light gases evolved.
Reaktionsverlaut während der härtung eines epoxidharzes mit dizyandiamid
Authors: Eyerer Peter 
Published: April 2003

AbstractNach einem kurzen Überblick über bisherige Untersuchungen an Epoxidharz–Dizyandiamid‐Systemen, wurde der Reaktionsverlauf eines handelsüblichen dizyandiamidhärtenden Epoxidharzes mittels Ultrarotspektroskopie verfolgt und mit den Ergebnissen früherer anderer Methoden am gleichen System verglichen. Dabei ergaben sich gute Übereinstimmungen hinsichtlich charakteristischer Reaktionszeiten (Polymerisationsbeginn, Polyadditionsbeginn, Vernetzungsende). Die Aktivierungsenergie für das Vernetzungsende wurde zu 20 kcal/mol bestimmt. Infolge einer Sedimentation der Dizyandiamidkristalle kommt es vor dem Polyadditionsbeginn zu einem völligen Entmischen von Harz und Härter. Mit Hilfe der Mikrohärtemessung ist es gelungen, den Reaktionsverlauf auch über der Schichtdicke zu erfassen. Zumischen von Quarzmehl verhinderte ein Absinken des Härters. Dadurch konnte die als Schwachstelle für Zugfestigkeitsmessungen wirkende Grenzschicht zwischen abgesunkenem Dizyandiamid und härterfreiem Epoxidharz vermieden werden. Außerdem erfolgte die Aushärtung über der Schichtdicke gleichmäßig. Als Folge ergaben sich für die gef¨︁llten Proben wesentlich höhere Zugestigkeiten.
Fractionation of linear polyethylene with gel permeation chromatography. IV
Authors: Nakajima Nobuyuki 
Published: April 2003

AbstractReproducibility was examined on the GPC fractionation of linear polyethylenes. The experiences over the period of two and a half years were used. Calibration was done with the same batches of narrow distribution polystyrene standards. A control sample of broad‐distribution polyethylene was run at each calibration. The reproducibility over ten calibrations with this control was in terms of standard deviation of ca. ±10% for the number‐average and ca. ±15% for the weight‐average chain length. The fractionation data of 36 commercial resins were corrected by using the control samples as an additional standard. The correction was very effective in decreasing the scattering of the data in the intrinsic viscosity–molecular weight plot, especially when the viscosity average was used for the molecular weight expression.
Fatigue of teflon bladder materials
Authors: Cuddihy Edward F. 
Published: April 2003

AbstractThe fatigue properties of Teflon laminates employed in the fabrication of liquid propellant expulsion bladders were studied by cyclically stretching specimens to constant load in order to achieve a correlation of cycles to failure versus the maximum stress amplitude. This approach provides a useful technique for evaluating the resistance of bladder materials to fatigue failure which could be caused by vibration‐induced cyclic loadings during ground testing and launch. Further, the data provides for a direct comparison of the relative fatigue properties of Teflon laminates and, in particular for those which were studied, the relative fatigue properties correlated with their ultimate breaking stresses. This observation, which suggests a simple and rapid method for evaluating relative fatigue behavior of candidate Teflon laminates, is discussed along with the effect of delamination on the fatigue properties observed for one laminate.
Polymer structure formed in radiation‐induced graft polymerization
Authors: Matsuzaki Kei , Kanai Taiichi , Morita Nobuyuki 
Published: April 2003

AbstractMethacrylic acid (MAA) and methyl methacrylate (MMA) were grafted onto nylon 6, cellulose triacetate, cotton, viscose rayon, and polyester fibers, and the stereoregularities of the grafted polymers were determined. The graft polymerization was carried out with preirradiation techniques using γ‐rays from a Co 60 source. The grafted copolymers were then separated from the homopolymers by Soxhlet extraction. The grafted (branch) polymers were isolated from the trunk polymers by acid hydrolysis and their stereoregularity was determined with a 100 MHz NMR spectrometer. The stereo‐regularity of PMAA or PMMA grafted onto viscose rayon or cotton fiber was different from that of the polymers formed in ordinary radical polymerization.
Pyrolysis and combustion of cellulose. II. Thermal analysis of mixtures of methyl α‐D‐glucopyranoside and levoglucosan with model phosphate flame retardants
Authors: Hendrix James E. , Drake George L. , Barker Robert H. 
Published: April 2003

AbstractThe thermal degradation of methyl α‐D‐glucopyranoside, a cellulose model of intermediate complexity, was investigated in an attempt to gain insight into the pyrolytic reactions of analogous cellulose systems. The pure glucoside pyrolysis proceeds through formation of an intermediate of higher thermal stability. Nitrogenous bases bring about decomposition of the glucoside at lower temperatures and without formation of a detectable intermediate. Phenyl phosphates and phosphoramides induce thermal degradation of methyl α‐D‐glucopyranoside at lower temperatures than observed for the pure glucoside. The postulated degradation mechanism involves esterification of the glucoside followed by dehydration and skeletal rearrangements. Nitrogenous bases assist the dehydration process but reduce the yield of residue and bound phosphorus. Levoglucosan, the cellulose degradation product responsible for flaming combustion, was pyrolyzed in the presence of model flame retardants. Nitrogenous bases were found to inhibit thermal polymerization of levoglucosan and to induce its decomposition at lower temperatures. Zinc chloride exerted its effects in two stages: acid‐catalyzed polymerization at lower temperatures and dehydration at higher temperatures. Phenyl phosphates and phosphoramides alter levoglucosan pyrolysis by action as Lewis acids in a manner similar to zinc chloride.
Color stabilization of poly(vinyl chloride) against high‐energy electron irradiation
Authors: Albarino R. V. , Otocka E. P. 
Published: April 2003

AbstractColor stability in irradiated PVC may be achieved by (1) structural modification to block dehydrochlorination, (2) addition of radiation protectors, or (3) addition of radical scavengers. This study explores the latter approaches. Twenty‐six compounds representing a variety of structural types were screened for their effectiveness as measured by subsequent color development. Fifteen of the compounds imparted partial or complete postirradiation stability. Possible stabilizer mechanisms are discussed.
Spinning of poly(ethylene terephthalate) fibers from a melt pool without a spinneret
Authors: Wampler F. C. , Gregory D. R. , Kennedy W. D. 
Published: April 2003

AbstractMonofilament fibers were spun continuously from the free surface of a pool of molten poly(ethylene terephthalate) without the aid of a spinneret. For take‐up velocities in the range of 12 to 400 ft/min, the denier of the filaments produced was an inverse power function of take‐up velocity, and the birefringence was an inverse power function of the filament diameter. Production rate and product uniformity were strongly dependent on take‐up velocity and surface temperature of the melt pool.
Preparation and properties of ABA block polymers of styrene and butadiene or isoprene made with sec‐C4H9Li·2(C2H5)2O
Authors: Cunningham Robert E. , Wise Mary L. 
Published: April 2003

AbstractABA‐type “tapered” block polymers were prepared from styrene (monomer A) and butadiene or isoprene, using an initiator of sec‐butyllithium complexed with two molecules of ethyl ether. The stress–strain curves of polymers containing about 20–50% styrene show the usual resemblance to curves of crosslinked elastomers. The SBS polymers had higher tensile strengths than the SIS polymers. They also had slightly higher tensile strengths than comparable SBS polymers made with sec‐butyllithium. The SIS polymers, however, had generally lower tensile strengths than those made with sec‐butyllithium. This is probably caused by higher styrene content of the isoprene block, brought about by increased randomization of the styrene–isoprene copolymerization due to the presence of the ether. The A and B blocks become more compatible, producing loss of strength in the polymer. Infrared analyses of polydienes made with the sec‐C4H9Li·2(C2H5)2O initiator showed a 6% to 8% increase in 1,2‐content (for polybutadiene) or 3,4‐content (for polyisoprene), compared to polymers made with sec‐butyllithium. The polymer microstructures still have high (>80%) total 1,4‐content, however. Thus, this amount of ether can be tolerated in the polymerization system without great loss of rubbery properties or block structure in the resultant polymers.
Thermal properties of unfilled cast cured sheets of polyesters based on bisacid A2
Authors: Lenk R. S. 
Published: April 2003

AbstractThe synthesis of bisacid A2 in a high state of purity, the preparation of unsaturated copolyesters therefrom, the preparation of solutions of the latter in suitable monomers, followed by casting of those solutions after addition of catalysts and curing of the material to obtain crosslinked polyester sheet, has been described in earlier communications.1–3 This paper deals with the heat distortion temperatures4 and the (modified) Vicat softening points5 of the cast sheets of various copolyesters at various monomer contents.