bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vapor phase polymerization of vinyl chloride
Authors: Kahle G. R. , Moberly C. W. 
Published: April 2003

AbstractA study of the polymerization of vinyl chloride was made at conditions under which the monomer exists in the gas phase. In the presence of a bed of poly(vinyl chloride) particles, free‐flowing product was obtained. By using free‐radical initiators, such as dialkylperoxy dicarbonates or acetylcyclohexane sulfonyl peroxide, high initiator productivities were obtained in reaction periods of 1.5 to 3 hr. Although some modifiers, such as ethyl bromomalonate and bromoform, were demonstrated to lower molecular weight, satisfactory molecular weight modification was accomplished by adjusting polymerization temperature. Several peroxy compounds of different reactivity were studied. Hydrocarbon additives improve the polymerization rate. It is believed that the hydrocarbon and initiator are absorbed on the PVC particle surface and allow the monomer concentration to be increased at the polymerization locus. PVC particles of small size may be prepared in a liquid bulk polymerization for use as seed polymer for the vapor phase process. This provides a seed of high porosity which enables one to prepare a vapor phase product with suitable plasticizer absorption. The physical properties of products prepared by the vapor phase process were evaluated in a rigid formulation.
Greffage radiochimique de l'acide acrylique sur les fibres de polyester
Authors: Bonnefis J. C. , Puig J. R. 
Published: April 2003

AbstractLe greffage par irradiation directe de fibres de polytéréphtalate d'éthylène glycol en contact avec des solutions aqueuses d'acide acrylique a été étudié dans les conditions suivantes: (a) irradiation par rayonnement gamma de 60Co entre 10.000 et 100.000 rads/hr pour des doses allant jusqu'à 1 Mrad; (b) irradiation par faisceau d'électrons des fibres imprégnées, avec des doses allant jusqu'à 4,5 Mrad. Les essais utilisant les rayons gamma se sont déroulés à des températures comprises entre 0°C et 90°C. Les influences des concentrations en monomère et an inhibiteurs sélectifs de l'homopolymérisation ont permis le choix des conditions opératoires les meilleures. La vitesse initiale de greffage est une fonction complexe du débit de dose puisqu'elle passe par un maximum vers 2,5 · 105 rad par heure à la température ambiante. La vitesse de greffage qui diminue avec la dose pour éventuellement s'annuler est une fonction croissante de la température. Deux énergies d'activation globales interviennent: 5,10 Kcal/mole entre 0°C et 55°C et 1,46 Kcal/mole au dessus de 55°C. Les fibres greffées contenant jusqu'à 40% de polyacide acrylique manifestent des propriétés intéressantes vis‐à‐vis de la reprise d'humidité, de l'affinité tinctoriale et de l'électricité statique, alors que leurs propriétés mécaniques ne sont pratiquement pas affectées. Les taux de greffage des plus utiles sont compris entre 15% et 20%.
Transport properties of eastman cellulose acetate membranes: Influence of diffusant size and shape on permeability
Authors: Osterhoudt H. W. 
Published: April 2003

AbstractEastman cellulose acetate membranes (acetyl content = 40%) have been studied by means of dialysis rate experiments with uncharged permeants of selected sizes and shapes. The experimental results show that the high flux membranes exert no molecular size or shape selectivity on the transport of permeants whose molecular weights are less than 1152. The membranes used in desalination, however, are selective as to molecular size and shape. Desalination membranes, therefore, may be useful in separations where differences in size and shape are present.
Continuous flow operation in emulsion polymerization of styrene
Authors: Nomura Mamoru , Kojima Hideki , Harada Makoto , Eguchi Wataru , Nagata Shinji 
Published: April 2003

AbstractThe kinetics of continuous emulsion polymerization of styrene were studied theoretically on the basis of the authors' batch reaction model, and a new reaction model was proposed for continuous operation. The validity of the model was tested by experiments conducted with stirred tank reactors in series. The characteristics of the first reactor used to generate polymer particles were studied in particular detail. It was found that there was an optimum residence time for the first reactor, the value of which was quantitatively predictable from the operating variables. The most suitable combinations of several types of reactors for continuous emulsion polymerization are also discussed.
The prediction of the tensile properties of flexible foams
Authors: Lederman J. M. 
Published: April 2003

AbstractAn idealized model for flexible foam in tension is developed. The model includes large deformations and cell structure orientation before and after deformation. It is predicted that two quantities affect the initial modulus of an unoriented foam: the density and a cell structure parameter. Data for latex foam show that the model correctly predicts the initial tensile modulus. The model also predicts that cell structure orientation is a reasonable method for achieving a desired modulus without altering the density.
Vapor permeabilities by dynamic sorption
Authors: Osburn James O. , Kammermeyer Karl , Laine Roney 
Published: April 2003

AbstractA new method of measuring the permeability of plastic films to vapors is described. The method is simple and convenient, uses general‐purpose equipment, and gives good results in a short time. It is easily adapted to vapors other than water vapor. This method is recommended for measurements of permeability where the expense of specialized equipment is not justified. Further studies on effects of parameters such as temperature, humidity, solvation of polymer, etc., are under way.
Synthesis of alternating polyamideurethans by reacting diisocyanates with N,N′‐di‐(6‐hydroxy‐caproyl)alkylenediamines and N‐hydroxy‐alkyl‐6‐hydroxycaproamide
Authors: Katayama Shitomi , Horikawa Hideichi , Ito Yoshihiro , Gomyo Noboru , Obuchi Yukio 
Published: April 2003

AbstractPolyamideurethans of structures I and II were prepared by reacting N,N′‐di‐(6‐hydroxycaproyl)alkylenediamines and N‐hydroxyalkyl‐6‐hydroxycaproamide with hexa‐methylene diisocyanate and 4,4′‐diphenylmethane diisocyanate:
magnified image
where R1 is either a dimethylene or hexamethylene radical, and R2 is a hexamethylene or 4,4′‐diphenylmethane radical. Polymers I and II were of a high degree of polymerization and crystallinity, had high enough melting points for practical use, and gave colorless tough films both by dry and melt castings. The polymers from hexamethylene diisocyanate were much more crystalline and thermally more stable above the melting points than those from 4,4′‐diphenylmethane diisocyanate. Polymerization conditions and characteristic properties of the resulting polymers were studied.
The mechanism of extender action by potassium persulfate in the suspension polymerization of styrene
Authors: MacLay William N. 
Published: April 2003

AbstractThe contribution by potassium persulfate to suspension stability in the bead polymerization of styrene which is stabilized by hydroxyl apatite (tricalcium phosphate) powders has been studied. Potassium persulfate, when used in lieu of an anionic surfactant as the extender, causes the formation of polystyrene sulfate in the aqueous phase. This anion‐active polymer adsorbs on the surface of the hydroxyl apatite crystals and thus alters their wetting characteristics, causing them to become more effective suspension stabilizers. Polystyrene sulfates of molecular weights ranging from 2000 to 100,000 have been synthesized, characterized, and shown to be effective hydroxyl apatite extenders. The capability of polystyrene sulfate to adsorb onto hydroxyl apatite crystals is not strongly dependent upon the molecular weight of the polymeric ester. The tolerance of the system to high molecular weight polystyrene sulfate is relatively high since excess extender is taken up by dissolving in the monomer phase. The tolerance for water‐soluble polystyrene sulfate, on the other hand, is low because excess extender of this type engages in double‐layer adsorption on hydroxyl apatite, which renders the latter too hydrophilic to permit effective suspension stabilization. Use of a water‐soluble polymerization inhibitor in the suspension polymerization system has no effect on suspension stability when sodium dodecylbenzene sulfonate or preformed polystyrene sulfate is used as the extender; however, suspension stability is destroyed when the inhibitor is used with persulfate, because it prevents the formation of polystyrene sulfate. Potassium persulfate is therefore more accurately described as a precursor of the active extender, which is the mono‐ or disulfate ester of polystyrene.
Effect of surface characteristics on polymer growth on titanium trichloride catalyst
Authors: Carradine William R. , Rase Howard F. 
Published: April 2003

AbstractLarge sublimed leaflets of titanium trichloride have been observed over a wide range of magnification both by optical and electron microscopy under conditions such that ethylene polymerization was slow enough so that its progress could be observed in detail. After treatment with triethylaluminum, a network of cracks develops on which polymer grows upon introducing ethylene. Polymer also appears on steps, crushed areas, and cleaved edges but not on as‐grown edges. The polymer appearing on lateral surfaces was nodular in character while that growing on basal surfaces was fibrous. The physical properties of these two forms may be different, and methods for favoring one or the other are suggested.
The effects of varying the polymer composition on the cut growth characteristics of E/P/1,4 HD tire treads
Authors: Stewart C. W. , Verbanc J. J. 
Published: April 2003

AbstractExperimental ethylene–propylene–1,4‐hexadiene polymers covering a range of compositions which possess satisfactory processing characteristics and economics have been evaluated in passenger car tires with emphasis on groove cracking. The tearing energy criterion was used in a laboratory test to correctly predict the groove cracking behavior of the tires made from these polymers. Road tests indicate that ethylene–propylene–1,4‐hexadiene tripolymers containing 36%–42% propylene and 1.8%–2.2% diene exhibit resistance to cut growth and abrasion which is superior to standard SBR–BR bias tires. Polymers containing more than 42% propylene or 2.2% diene were inferior in wear and resistance to groove cracking, but sufficient data are not available to pinpoint the reason.
Strain rate dependency on stress–strain relations of polypropylene
Authors: Kobayashi Akira , Ohtani Nobuo 
Published: April 2003

AbstractTrue constant strain rate tensile tests of polypropylene up to 2% initial strain were performed to investigate the strain rate dependency of the initial stress–strain gradient dσ/dε with the aid of “slack grip.” The experimental results fairly agree with even the simplest mechanical model analysis with three parameters, showing the conspicuous strain rate dependency on the initial stress–strain gradient dσ/dε. The limiting cases corresponding to zero strain rate and strain rate of infinite magnitude, both predicted by the analysis, were experimentally verified.
Protection against intense light. I. Discussion of the usual mechanisms of energy dissipation
Authors: Prosser R. A. 
Published: April 2003

AbstractThe relative thermal protection offered by a series of halogenated vinyl polymers is discussed in terms of the usual modes of energy attenuation and dissipation, such as reflection, endothermic decomposition, etc. It is shown that none of these modes is so overwhelming that it alone can account for the relative thermal protection offered by these polymers.
Adsorption of polyamides and the stability of dispersion
Authors: Sato Tatsuo 
Published: April 2003

AbstractThe stability of red iron oxide, titanium dioxide, and carbon black dispersed in cyclohexanone and isopropyl alcohol solutions of fatty polyamides was studied by measuring adsorption, viscosity, zeta potential, and sedimentation volumes. It was found that the stability of dispersion is markedly affected by the adsorption of polyamides. The greater the amount of adsorption, the greater the stability. On the other hand, a negative adsorption impaired the stability. A stabilization mechanism of polyamide adsorption was discussed in terms of entropic repulsion, electrostatic repulsion, and van der Waal's attraction.
Rheology of shaped fiber formation
Authors: Han Chang Dae 
Published: April 2003

AbstractA rheological interpretation is given for the formation of shaped fibers whose cross section is different from the spinnerette shape. For the study, a rectangular die having an aspect ratio of 6 was constructed, with dimensions 0.1 in. by 0.6 in. Measurements were then taken of the distributions of wall normal stresses at two adjacent walls of the rectangular duct. The measurements show the nonuniform distributions of wall normal stresses over the long and short sides of the rectangle, which is in accord with the nonuniform distributions of extrudate swell on both sides of the rectangle. Explanations are then given for the observed fact that extrudate swell is more pronounced at the long side than at the short side.
Studies on the ability of cellulosic materials to initiate graft copolymerization
Authors: Ogiwara Yoshitaka , Igeta Kikuji , Kubota Hitoshi 
Published: April 2003

AbstractThe activity to initiate graft copolymerization was investigated for various cellulose samples. Oxidation of the sample with hydrogen peroxide or sodium hypochlorite indicated a remarkable increase in the per cent grafting as well as the number of grafts. This phenomenon must be attributed to the formation of special reactive groups in cellulosic materials. However, the treatment with hot water caused a definite decrease in the per cent grafting or the number of grafts for the graft copolymerization on the sample, indicating a lower activity to initiate graft copolymerization. Accordingly, the reactive groups, once formed on the sample by oxidation, seemed to be easily decomposed by hot water. The ferric ion adsorbed on cellulose increased the per cent grafting and accelerated the formation of grafts, and the contribution of metallic ions to the initiation was recognized as one of the important factors of graft copolymerization.
Rheological properties of molten polymers. I. Homopolymer systems
Authors: Han Chang Dae , Yu Thomas C. , Kim Kwang Ung 
Published: April 2003

AbstractExperimental work has been carried out to investigate the influence of molecular weight distribution and long chain branching on both viscous and elastic properties of molten polymers, using a capillary rheometer, as described in a recent paper by Han. The materials used for the study are three high‐density polyethylene samples of widely different molecular weight distributions and a low‐density polyethylene containing much long‐chain branching. For the analysis of the experimental data, and to obtain the information on the melt elasticity, the concept of the exit pressure recently advanced by Han is used. The study shows that the sample containing long‐chain branching is much more elastic than the samples containing little or no long‐chain branching, and that the broader the molecular weight distribution of the material, the more elastic the material is. These findings are in conformity with those reported in the literature. Also studied were blends of two high‐density polyethylenes having widely different molecular weight distributions. The results of the blends systems show a maximum in melt viscosity as well as in elasticity for a certain blending ratio. The results of the present study may be of considerable interest to those who are concerned with modifying the structure of polymer and also with determining optimum processing conditions.
A novel method for preparing poly(alkyl methacrylates) and poly(methacrylic acids) of varying tacticity
Authors: Chlanda Frederick P. , Donaruma L. Guy 
Published: April 2003

AbstractIn order to synthesize poly(methacrylic acid) and poly(alkyl methacrylates) over a wide range of polymer tacticity, the anionic polymerization of the following alkyl methacrylates (ethyl, n‐propyl, isopropyl, n‐butyl, sec‐butyl, isobutyl, tert‐butyl, n‐amyl, n‐hexyl, n‐octyl, n‐decyl, n‐lauryl, and n‐octadecyl) in toluene using phenylmagnesium bromide initiation was studied. It was found that the amount of isotactic polymer structure generally decreased as the size of the ester group increased. In all cases, the polymers had greater than 50% isotactic triad structure. Whether the polymerization was carried out at 0° or −78°C had little or no effect on the tacticity of the polymer produced. It was found that the poly(alkyl methacrylates) produced could be hydrolyzed in concentrated sulfuric acid to poly(methacrylic acid). The poly(methacrylic acid) produced in the hydrolysis could be esterified with diazomethane to give poly(methyl methacrylate) or with diazoethane to give poly(ethyl methacrylate) with the same tacticity as the poly(alkyl methacrylate) from which the poly(methacrylic acid) was derived. It is possible, therefore, to produce poly(alkyl methacrylates) of a desired tacticity by polymerizing the appropriate monomer, hydrolyzing, and reesterifying the resultant poly(methacrylic acid) with a diazoalkane to give the desired poly(alkyl methacrylate).
Synthetic biologically active polymers. VI. Sulfonamide‐ and sulfone‐dimethylolurea copolymers
Authors: Dombroski John R. , Donaruma L. Guy 
Published: April 2003

AbstractDimethylolurea was found to copolymerize with a number of sulfonamides and sulfones (Ia–h) to yield oligomeric condensation products (IIa–h). The preparation and characterization studies relevant to these materials are described. Products IId, IIf, IIg, and IIh were active as antimalarial drugs.
The effect of short‐chain branch structure on the properties of low‐density polyethylene
Authors: Mortimer George A. 
Published: April 2003

AbstractIn order to determine the effect of the molecular structure of short side branches in lowdensity polyethylene upon the physical properties of the resin, a study was carried out in which small amounts of various comonomers were added to an otherwise relatively unbranched polymer. It was found that linear short side branches have about the same effect in decreasing stiffness and increasing toughness as the natural short‐chain branches of polyethylene have. However, branches containing a tert‐butyl group increased resin toughness more than linear branches while decreasing stiffness by about the same amount. Thus, by adding a small amount of branched, short side branches, it is possible to obtain an optimum balance of physical properties not obtainable from low‐density ethylene homopolymer.
Infrared studies of cryogenic transitions in poly(ethylene terephthalate) and polystyrene
Authors: Huang Y. S. , Koenig J. L. 
Published: April 2003

AbstractInfrared absorbance measurements as a function of temperature down to 13°K have been made on poly(ethylene terephthalate) and polystyrene. Transition temperatures are assigned to the temperatures where there are abrupt changes in the absorbance or integrated band intensities. Bands of known structural origin arising from either crystal‐line or amorphous phases are studied to probe the structure basis and environment effect for each transition. Transitions are found around 50, 120, 180, and 220°K for PET and around 50° and 235°K for polystyrene.
Composite membranes for seawater desalination by reverse osmosis
Authors: Riley R. L. , Lonsdale H. K. , Lyons C. R. 
Published: April 2003

AbstractA composite reverse‐osmosis membrane has been developed for seawater desalination having a 400‐Å semipermeable barrier. The membrane is prepared by directly forming a very thin film of a polymer, generally cellulose triacetate, upon the finely porous surface of a supporting membrane. The composite membrane, capable of desalinating seawater in a single pass, has demonstrated improved flux stability at high pressures over modified membranes currently used to desalinate brackish water.
The application of thermogravimetric analysis to an electrophoretically deposited polymer coating
Authors: Levine Solomon L. , Bell Harry F. 
Published: April 2003

AbstractAn electrophoretically deposited poly(vinylidene chloride)–poly(vinyl chloride) and epoxy ester coating has been shown to provide adequate protection for Be‐Cu from hostile environments. The data presented show that thermogravimetric analysis can be readily applied for drying analysis and quality control of the polymer ratio.
Thin water vapor barriers for paper
Authors: Liepins R. , Kearney J. 
Published: April 2003

AbstractLow‐pressure plasma technique was used in the deposition of thin polymeric coatings upon a filter paper. Sixteen different monomers, including aromatic and aliphatic hydrocarbons, nitriles, chlorine‐containing compounds, and a silane, were used in the coatings. Most of the coatings functioned as water vapor barriers in different degrees, and the coated samples possessed wet tensile strengths anywhere from 3 to 34 times that of the untreated samples. Attenuated total reflectance infrared spectroscopy was used to study the chemical structure of the coatings.
Cure behavior of some resin–glass cloth systems
Authors: Jenkins Robert K. , Lister James 
Published: April 2003

AbstractChanges in the dynamic modulus E′dyn of some phenolic glass cloth systems were studied as a function of cure temperatures and formaldehyde factors. The modulus changes were followed by continuously monitoring in situ the fundamental frequency of vibration of resin‐impregnated glass cloth systems bonded to metallic cantilever reeds. The apparent activation energy of crosslinking was a direct function of the formaldehyde content in the resin synthesis, ranging from 9 kcal/mole for a 1.2 formaldehyde factor phenolic, to 20 kcal/mole for a 1.8 factor. Two cure parameters at 50% and 100% apparent mechanical conversion were established.
Studies on sulfur vulcanization of natural rubber accelerated with diphenylguanidine both in presence and absence of dicumyl peroxide
Authors: Manik S. P. , Banerjee S. 
Published: April 2003

AbstractDiphenylguanidine acceleration of sulfuration of natural rubber both in the presence and absence of dicumyl peroxide (DCP) has been studied. DPG enhances the rate of decomposition of DCP, and the crosslinking maxima due to DCP are lowered by DPG to some extent, which increases with the concentration up to a limiting value. The rate of sulfur decrease is very high and is dependent on DPG concentration but practically independent of the presence of ZnO and stearic acid. It is observed that with constant level of DCP and sulfur, crosslinking increases with the increase of DPG concentration and finally becomes additive when the molar proportion of DPG: S8 approximately equals 1:1. In presence of ZnO and stearic acid, with each increment of DCP concentration crosslinking is retarded for both systems. Mechanisms have been suggested in terms of polar and radical process.
Surface morphology of polyethylene after treatment in a corona discharge
Authors: Kim C. Y. , Goring D. A. I. 
Published: April 2003

AbstractCorona treatment of low‐density polyethylene in oxygen or oxygen‐containing gases produced bumps on the surface, while treatment in nitrogen, hydrogen, argon, or helium caused no detectable surface change. Bumps made by an oxygen corona increased in size with time and temperature of the treatment. The bumps were removed when a treated polymer sheet was dipped into solvents such as CCl4, ethanol, or 0.2% aqueous NaOH. Infrared analysis indicated that most of the oxidized layer was eliminated from the polymer surface by solvent dipping and that the degraded products contained a substantial proportion of CH2 groups. It is suggested that the bumps are caused by the migration of low molecular weight degradation products to charged areas of the polymer surface.