bluuebunny/crossref_metadata_2025_split huggingface dataset:
A measure of effective crosslinks in formaldehyde‐modified cotton celluloses
Authors: Rowland Stanley P. , Post Arnold W. 
Published: April 2003

AbstractSol‐gel fractions have been measured for cotton celluloses crosslinked with formaldehyde under widely different conditions of reaction and have been employed for estimation of the efficiency of crosslinking in the various processes. Most efficient utilization of formaldehyde for insolubilization of molecular chains is indicated for an aqueous process (form W′) and least efficient utilization is indicated for a nonaqueous process (form D′), the difference in efficiency being approximately a factor of 40. Interpretation of sol‐gel data has been made relative to a model assuming random reaction of crosslinking agent throughout the cotton cellulose and by relationships developed by Charlesby and Pinner and by Shultz. This leads to estimates of relative numbers (moles) of effective chain elements per gram, ve (i.e., twice the number of effective crosslinks), which decrease in the following sequence for cottons at the 0.20% level of formaldehyde (i.e., 6.7 × 10−5 mole/g.): aqueous process, higher formaldehyde concentration (W′, ve = 4.8 × 10−5), vapor process (V, ve = 1.75 × 10−5), bake‐cure process (C, ve = 1.37 × 10−5), aqueous process, lower formaldehyde concentration (W, ve = 0.95 × 10−5), nonaqueous process (D, ve = 0.03 × 10−5).
Inhibited oxidation of vulcanized natural rubber
Authors: Bevilacqua E. M. 
Published: April 2003

AbstractRates of oxidation in oxygen at 140°C. of natural rubber gum vulcanizates containing PBNA as inhibitor have been compared. They are a function of sulfur combined with the rubber, and only slightly affected by curing system for sulfur alone, TMTD sulfurless, and very high‐efficiency sulfenamide plus dithiocarbamate‐accelerated compositions. Addition of diphenylguanidine to simple sulfur vulcanizates causes much faster oxidation. No conclusions about oxidation mechanism can be drawn from rates of oxidation alone.
Thermal stability of elastomeric networks at high temperatures
Authors: Lee T. C. P. , Sperling L. H. , Tobolsky A. V. 
Published: April 2003

AbstractStress relaxation experiments were carried out in a dry nitrogen atmosphere on polydimethylsiloxane and an ethylene‐propylene terpolymer. Relaxation times much longer than expected were observed, and plots of In f(t)/f(0) versus time were linear in all cases.
Gelation and fusion of vinyl plastisols
Authors: Hoy K. L. 
Published: April 2003

AbstractThe gelation of vinyl plastisols at constant temperature has been found to follow the equation ln [(C − Ce)/(U − Ce)] = (− π2/a2)Dτ + ln (8/π2), where C is the resin phase concentration, Ce the equilibrium resin phase concentration, U the critical resin phase concentration, a the average particle size, D the diffusion constant, and τ the time required for the onsent of gelation. A light reflectance apparatus capable of measuring the gelation process is described. The effect that various resin–plasticizer parameters have on the gelation and fusion process is discussed. The light‐reflectance apparatus is also useful for estimating various resin and formulating parameters.
Molecular weight distribution in alkyd resins. Part III. Presence of microgel in alkyd resins
Authors: Solomon D. H. , Hopwood J. J. 
Published: April 2003

AbstractAlkyd resins which have the same overall chemical composition and the same degree of polymerization have been prepared from synthetic mixtures of mono‐, di‐, and triglycerides of linoleic acid, glycerol, and phthalic anhydride. The properties of these resins differend significantly. Microgel particles are present in all resins, but the quantity and size of the gel particules is a function of the glyceride composition. The concept of microgel is used to explain the solution and film forming properties of these resins. Examination of a range of commercially available alkyd resins has shown that microgel particles are present where the functionality is greater than two.
Polymers for stabilization of colloidal cobalt particles
Authors: Hess Patrick H. , Parker P. Harold 
Published: April 2003

AbstractA process for preparing metiallic cobalt particles of uniform size in the 10–1000 A. range is described. Dicobalt octacarbonyl is thermally decomposed in solutions of dispersant polymers to form stable colloids of discrete particles which are separated by polymer coatings. Variatin of polymer composition, molecular weight, and solvent used results in a variation of particle size and colloid stability. Preparation of single‐domain ferromagnetic cobalt particles with good magnetic properties depends on a very delicate balance between dispersant polymer, solvent, and the growing metal particle. A number of addition and condensation polymers can act as dispersants. The most successful are linear addition polymers of high molecular weight having relatively nonpolar backbones. Ideally, groups with a polarity greater than the backbone are attached at intervals of at least 100 but not more than 200 backbone atoms. The need for more polar groups and their spacing becomes les critical with increasing polymer molecular weight. The polymers appear to stabilize the metal particles by adsorption to form a thick fiml which separates the particles sufficiently to keep van der Walls energy of attraction below thermal energy levels. The solvent must solubilize the polymer coating sufficiently to allow the particle to grow. It should be less polar than the most polar group in the polymer and be chemically inert.
Emulsion polymerization of ethylene. V. Kinetics and mechanism
Authors: Stryker H. K. , Mantell G. J. , Helin A. F. 
Published: April 2003

AbstractThe solubility of ethylene was measured in water, water–tert‐butyl alcohol, water‐emulsifier, water‐tert‐butyl alcohol‐emulsifier, and water–tert‐butyl alcohol–emulsifier–polyethylene. The polymerization of ethylene in an emulsion system differs from that of other vinyl monomers in several ways: the rate of polymer formation is inversely proportional to the emulsifier concentration and to the number of particles, the molecular weight of the polymer increases as the particle size increases, the polymer contains bound emulsifier whose concentration depends inversely on the particle diameter. These peculiarities are attributed to a transfer reaction between polymer radicals and emulsifier adsorbed on the surface of the polymer particle. In the presence of a fatty‐acid soap, the transfer probably occurs primarily at the carbon α to the carboxyl group.
Melt flow and strength of branched styrene copolymers
Authors: Toggenburger R. , Newman S. , Trementozzi Q. A. 
Published: April 2003

AbstractIn order to assess the dependence of strength properties of glassy polymers upon the extent of branching, copolymers of poly(styrene–acrylonitrile) were prepared. By using principally three methods: (a) hydroperoxide intermediates, (b) hydroxyl radical initiation, and (c) incorporation of transfer monomers, branched polymers with high levels of branching with comb and dendritic type structures were generated. The tensile strength was found to be strongly correlatable with melt flow, and, in general, the branched copolymers were found to have the same tensile strength as linear polymers of the same melt index.
Polyurethane elastomers from post‐grafted polymer–polyol systems
Authors: Kuryla William C. , Whitman Robert D. 
Published: April 2003

AbstractCertain homopolymer–polyol mixtures, after treatment with a free‐radical generating agent or ionizing radiation, will produce polyurethane elastomers of nearly twice the stiffness and tensile properties compared to control elastomers made with untreated mixtures. Specific examples of these mixtures include the homopolymers of acrylonitrile and vinyl chloride with a poly(oxypropyl) triol of about 3000 molecular weight as the polyol in each case. The marked improvement in the stiffness and tensile properties of elastomers made with the treated mixtures over those of the untreated controls indicates a grafting process occurring between the polyol and homopolymer upon the generation of free radicals. In the present work, grafting could occur by a chain‐transfer hydrogen‐abstraction mechanism, whereby a free‐radical site is generated on both the homopolymer and polyol chains. Coupling of these two free‐radical sites would thus result in the establishment of a polymer–polyol graft bond.
Thermal oxidation and photo‐oxidation of poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Kelleher P. G. , Jassie L. B. , Gesner B. D. 
Published: April 2003

AbstractThe thermal oxidation and photo‐oxidation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) have been examined. Oxidation of the plastic results in the evolution of carbon dioxide, nitrogen and traces of hydrogen, the introduction of considerable crosslinking, and increased absorption in the hydroxyl and carbonyl regions of the infrared spectrum. A free‐radical oxidation mechanism is postulated.
Some mechanical properties of an epoxy resin system cured with multiple crosslinking agents
Authors: Jenkins Robert K. 
Published: April 2003

AbstractArbitrary cure times and glass transition temperatures are reported for an epoxy resin cocrosslinked by various weight fractions of hexamethylenediamine (HMDA) and m‐phenylenediamine (m‐PLDA). The glass transition temperatures of the epoxy resin systems studied yielded an excellent fit to an empirical equation developed by Dyvik for copolymers. The cure time parameters were found to be a linear function of the weight fractions of each crosslinking agent present. The mechanical properties of the epoxy resins were measured by an in situ dynamic modulus technique which employed the use of a resin‐coated metallic substrate.
Plasticizer diffusion as the rate‐determining step in dry blending of poly(vinyl chloride)
Authors: McKinney P. V. 
Published: April 2003

AbstractDifferential thermal analysis has been used to examine the process of dry blending of plasticizer and PVC. The rate of transformation of the glass transition from that of the polymer initially in the cold mix to the glass transition of the blend (blend Tg) has been examined at various temperatures from room temperature to above the polymer Tg. The dependence on temperature of this rate of transformation of the observed Tg is similar to the temperature dependence of the diffusion of plasticizer into PVC. It is concluded that diffusion of plasticizer into polymer particles is the rate‐determining step in the dry blending of PVC. It also appears that a single mechanism of diffusion is involved both below and above the glass transition of the polymer.
Contact angle characteristics and breaking strength of paint plastic film
Authors: Tamai Y. , Tanaka S. 
Published: April 2003

AbstractThe advancing contact angle of water on plastic film coatings on metal was measured against both the air and the metal side surfaces after their being peeled off from the metal substrate. The plastic used was a methacrylate copolymer, and it was baked on cadmium, aluminum, nickel, iron, and gold. Contact angle for the air side was about 74° at 25°C. for all metals, but the values on the metal side differed considerably, ranging from 76° for gold to 50° for cadmium. At the same time the static breaking strengths of the same films were investigated by applying a knife‐edge vertically to the film with increasing load and measuring the weight at which the electric resistance through the film became zero. Increasing film thickness gave increasing strength, but further thickening made the film weaker with a tendency for crack formation. The film–metal combinations of larger contact angle difference generally also showed the higher breaking strength.
Polymer degradation. V. Changes in molecular weight distributions during sonic irradiation of polyisobutene
Authors: Porter Roger S. , Cantow Manfred J. R. , Johnson Julian F. 
Published: April 2003

AbstractGel permeation chromatography was used to follow changes in the molecular weight distribution of a polyisobutene, initial Mv = 466,000, during degradation induced by sonic irradiation. Seven samples taken at times of 200–163,500 sec. were studied. In general, a steady decrease in molecular weight was observed, although a bimodal distribution was present after 20,000 sec. irradiation. Various measures of inhomogeneity, Mw/Mn, U, etc., were examined. The function, σn/Mw, where σn is the standard deviation of the number distribution, is considered as a measure of the relative distribution. It is shown to be almost constant throughout the degradation.
Dynamic properties of PBNA–natural rubber vulcanizates
Authors: Payne A. R. 
Published: April 2003

AbstractSome crystalline organic compounds containing a β‐naphthyl group stiffen rubbers considerably. This paper discusses the dynamic behavior of these systems when subjected to oscillatory strain of increasing amplitude. Modulus–strain amplitude plots similar to that in carbon black–natural rubber systems are obtained. The implication of these results to reinforcement theory is discussed.
Effect of molecular weight distribution on viscosity of polymeric fluids
Authors: Middleman Stanley 
Published: April 2003

AbstractBueche's theory is modified to account for the effect of polydispersity on viscosity of polymeric fluids. Results indicate that the ratio of weight‐average to number‐average molecular weight, 〈Mw/Mn〉, though a common measure of polydispersity, is insufficient to account completely for the effect of polydispersity on viscosity.
Synthèse et caractérisation de copolymères cellulose–poly(méthacrylate de méthyle): Greffage par le système acide de Caro–ion Fe3+
Authors: Miléo Jean‐Claude , Nicolas Louis 
Published: April 2003

AbstractLe méthacrylate de méthyle a été greffé a la cellulose en utilisant l'acide de Caro en présence de sel ferrique comme initiateur. L'effet de la durée du greffage, de la concentration en ions ferriques et du rapport cellulose‐monomere sur le pourcentage du greffage a été étudié. Au départ d'études du mécanisme de réaction, a des composés modèles, on a admis que les greffages ne se passent pas via les unités glycols 1,2 ou à l'unité hémiacétalique ' la fin de la molécule cellulosique. Des dégradations concommittantes de la cellulose en cours de la copolymérisation greffée a été examinée. Une relation linéaire entre le pourcentage de greffage et le nombre de chaînes cellulosiques briées par hydrolyse a été trouvée, d'où il semble que la structure du copolymère greffé était plutôt du type séquencé. La structure du copolymere greffé a aussi été étudiée par détermination des poids moléculaires des branches de polyméthacrylate de méthyle greffées apres hydrolyse de la chaîne cellulosique. Dans tous les cas, indépendamment des conditions de réaction, les poids moléculaires des ramifications greffées étaient tres élevés et leur nombre faible. Le nombre de branches greffées par chaîne cellulosique a été calculé au départ du pourcentage de greffage, des poids moléculaires des branches de polyméthacrylate et des poids moléculaires de la chaîne cellulosique. Ce nombre a été comparé au nombre de liens cellulosiques brisés en cours de greffage.
Graft copolymers of starch. III. Copolymerization of gelatinized wheat starch with acrylonitrile. Influence of chain modifiers on copolymer composition
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E. 
Published: April 2003

AbstractA study was made of the influence of selected chain modifiers on both the molecular weight of grafted polyacrylonitrile and the grafting frequency of the starch–polyacrylo‐nitrile graft copolymer. Gelatinized wheat starch was used with ceric ammonium nitrate as the initiator. The organic chain modifiers investigated were ethyl mercaptan, 1‐dodecanethiol, methyl ethyl ketone, acetaldehyde, and chloroform. Sodium chromate, cupric bromide, cupric nitrate, cupric acetate, and cupric chloride were also tested as chain modifiers. In the presence of cupric chloride, there was a tenfold reduction in the molecular weight of grafted polyacrylonitrile; however, fewer chains were grafted to the starch backbone than were observed without cupric chloride.
Evaluation of polyglycidyl esters as cryogenic adhesives
Authors: Sandler Stanley R. 
Published: April 2003

AbstractPolyglycidyl esters of aromatic polycarboxylic acids were evaluated as adhesives for aluminum over the temperature range −453 to +400°F. The esters were cured either with amines or anhydrides. Cyclopentanetetracarboxylic acid dianhydride was found to be a superior curing agent and gave adhesives with tensile shear strengths in excess of 1000 psi at 400°F.
Investigation of conditions of spherulite formation in mixtures of crystalline and amorphous polymers
Authors: Bartoň J. , Rak J. 
Published: April 2003

AbstractThe supermolecular structure of mixtures of crystalline polymers (low pressure and high pressure polyethylene, isotactic polypropylene) with an amorphous polymer (atactic polypropylene) from the point of view of the influence of the amorphous component on the morphology of the crystalline component has been investigated. The criterion of changes in the morphological state of larger supermolecular formations was the microscopic image of the samples obtained with an optical microscope, both between crossed nicols and in phase contrast. It has been established that the formation of typical spherulites depends on the amount of admixture of the amorphous polymer and also on the treatment of the samples. Upon crystallization in presence of a small amount of solvent (p‐xylene), formation of typical spherulites of the crystalline component of the mixture can be observed while the same mixture in case of evaporation of the solvent presents a granulated refractive structure without typical spherulites, regardless of the rate of cooling. The probable role of the solvent is to facilitate mutual segregation of the microphases of both polymers in consequence of decrease in viscosity of the mixture. It has been further shown that even after briefly heating the mixture to a temperature of 220°C., before crystallization, spherulites do not form; on the contrary, spherulites originally present disappear and a structure consisting of smaller refractive formations of crystalline polymer is obtained. The formation of this structure, emerging after destruction of spherulites, might be attributed to an increase of interpenetration of both polymers and to an increase of the contact surfaces between components of the mixture.
Effect of environmental hydrogen pressure on the hydrogen yield from x‐irradiated polyethylenes
Authors: Hill Otto H. , Lightfoot R. Pat 
Published: April 2003

AbstractAn experimental assembly incorporating a capacitance‐type, differential pressure transducer, which provides resolutions of 3 × 10−4 torr at pressures extending to 30 torr, has been employed to monitor the effect of hydrogen environmental pressure on the hydrogen yield from x‐irradiated polyethylenes. Contrary to the observations of previous investigators, the hydrogen yield is found to be independent of hydrogen environmental pressures extending over the critical range up to at least 30 torr. It is demonstrated that neglecting the temperature and density gradients inherent in closed‐volume irradiation assemblies employing cryogenic traps to separate liberated gases into condensable and noncondensable fractions may lead to erroneous conclusions with respect to gas yields arising from the irradiation of materials. A homogeneous, variable‐plate separation ion chamber consisting of a polyethylene body and utilizing flowing ethylene as the cavity gas was employed to obtain total volatile G values of 3.6 ± 0.4, 3.8 ± 0.4, and 4.0 ± 0.4 molecules/100 e.v., for Marlex 6002, Dow Ziegler (Q 917.5), and DuPont A‐1410 polyethylenes, respectively. A hydrogen contribution of approximately 98 mole‐% was obtained with this experimental method.
Silane polysulfide polymers as solid composite propellant binders
Authors: Schwarz William W. , Lowrey R. Dean 
Published: April 2003

AbstractTwo mercaptosilane monomers were prepared and polymerized by oxidation to yield mercaptan functional silane polysulfide polymers. The mercaptosilane monomers were of the general formula, [HS(CH2)x]2SiY2, where x = 3 and Y = Et or Me. These monomers were prepared by the addition of thiolacetic to diallyldialkylsilanes. The dithioldiacetate that resulted from the addition reaction was hydrolyzed in alcoholic NaOH yielding the dimercaptan. Polymerization of the dimercaptan was accomplished with peroxides, iodine, or sulfur, yielding polymers of a molecular weight of approximately 1200. These polymers were cured to solid elastomers with mild oxidizing agents. The mercaptan monomers were also redistributed with diethylformal polysulfide polymers, which were then cured to solid elastomers with mild oxidizing agents. The redistributed silane–diethylformal polymers were used to make composite solid propellants. A 50% increase in propellant burning rate and a 16°C. lowering of the glass transition temperature were found when the redistributed polymer was used in place of diethylformal polymers as a propellant binder. Experimental procedures are given.
Molecular weight distribution in disulfide polymers
Authors: Shlyakhter R. A. , Ehrenburg E. G. , Nassonowa T. P. , Piskarewa E. P. 
Published: April 2003

AbstractThe published data on molecular weight distribution in polysulfide are rather contradictory and cannot be correlated with the concept of the existence of thiol–disulfide interchange in these polymers. In the present work the viscosity and molecular weights of liquid thiokols have been investigated (the number‐average molecular weight by iodometric titration and by ebulliometry and the weight‐average molecular weight by the light‐scattering method). When measuring the light scattering in Thiokol Solutions a considerable depolarization of the scattered light was observed. This fact must be taken into account in the molecular weight determination. It has been established that in polydisulfides with thiol endgroups thiol–disulfide interchange reactions take place not only during the synthesis, but also in the polymer itself (in bulk). These reactions lead to the formation of polymers with an equilibrium molecular weight distribution. A relation of log η = f(Mw)½ has been found that can be used in determining the weight‐average molecular weight of liquid Thiokols.
Viscoelastic investigation on the cure of unsaturated polyester coatings
Authors: Imai T. 
Published: April 2003

AbstractThe change of the viscoelastic behavior of an unsaturated polyester resin during curing was followed by a vibrometric technique, while the portion converted to gel in applied films was also determined by means of extraction with a solvent. Some relationship between the viscoelastic properties and the amount gelling has been found to exist. The dependency of the curing rate of polyesters on the concentration of initiator as well as accelerator seemed not to be unity. A marked delay in cure has been observed in the region of low concentrations of initiator and accelerator.
Elastomers from castor oil
Authors: Ghatge N. D. , Phadke V. B. 
Published: April 2003

AbstractCastor oil has been used to prepare millable elastomers by using 2,4‐toluene diisocyanate, 4,4′‐diphenylmethane diisocyanate, and 1,5‐naphthalene diisocyanate, respectively. These elastomers are vulcanized with sulfur and 4,4′‐diphenylmethane diisocyanate separately by using the standard methods of rubber technology, and the properties of these vulcanizates are reported.