bluuebunny/crossref_metadata_2025_split huggingface dataset:
Factors affecting the promoted aggregation and coalescence of synthetic rubber particles
Authors: White W. W. , Reynolds J. A. , Gilbert R. D. 
Published: April 2003

AbstractSmall particles (ca. 700 A.) in an SB‐R latex can be agglomerated (aggregation and coalescence) to the large size and heterogeneous distribution required for fluid high solids latex. This agglomeration is promoted by high molecular weight materials such as polyvinyl methyl ether (PVM). The mechanism of this agglomeration has been investigated. The effects of controlled variations in the amounts of PVM, electrolyte, soap and latex solids content were determined using statistically designed experiments. The agglomeration was found to differ from Smoluchowski kinetics in that it could best be described by the relationship: (1/n) = (1/n0) + at − bt2 where n = particle number, t = time and a and b are constants. The agglomeration rates were about 1011 to 1012 times slower than the theoretical Smoluchowski rapid coagulation rate. Increases in PVM, soap, and latex solids increased the agglomeration rate. The agglomerations were self‐limiting and reached equilibria the level of which increased with increases in PVM and decreased with increases in soap. Regression equations relating the effects of the controlled variables on the agglomeration rate and the equilibria states are derived and presented graphically. The particle size distribution of the final latex was significantly correlated, with that expected from theoretical collision theory.
Effect of the concentration of phenyldichlorophosphine and reaction time on the intrinsic viscosity of copolymers of methyl methacrylate with phenyldichlorophosphine
Authors: Łaszkiewicz Bogumił 
Published: April 2003

AbstractThe relation between the intrinsic viscosity of methyl methacrylate–phenyldichlorophosphine copolymers and the copolymerization time were investigated. The copolymers of methyl methacrylate and phenyldichlorophosphine were prepared at mole ratios of 1:10.012, 1:0.026, and 1:0.062, respectively. The experiments indicate that the intrinsic viscosity of copolymers increases at the first stage of copolymerization and then decreases after reaching a maximum. These changes of the intrinsic viscosity can be explained by degradation and by small relative activity of organophosphorus comonomers.
Physicochemical studies of cellulose acetate decomposition reactions
Authors: Parks L. R. , Sperling L. H. 
Published: April 2003

AbstractThis work is a continuation in these laboratories of the study of the source of undesirable optical properties of molded cellulose acetate. The origin, mechanism of formation, and structure of the colored compounds formed upon heating cellulose acetate in the presence of plasticizer were studied. Extraction of heated mixtures gave evidence indicating the colored compounds are intermediates containing a conjugated carbonyl group. Efforts to fractionate and isolate color‐causing fractions were defeated by the well‐known solvent inclusion difficulties and upset of the little‐understood salt balance in the sample. The effects of additives known to degrade cellulose acetate were determined by heating mixtures of these materials with cellulose acetate dissolved in excess plasticizer. Acidic compounds caused the expected severe degradation and color formation. Air oxidation and free radical initiators had very little effect compared to the acidic materials. Inhibitors of the action of acidic compounds (neutralizers) and of oxidative degradation were studied.
Dielectric properties of an epoxy resin
Authors: Dasgupta S. , Mital P. K. 
Published: April 2003

AbstractThe dielectric properties of an unmodified epoxy resin with a wide range of hardener content were investigated over the frequency range 5 cycles/sec. to 50 Mcycles/sec and over the temperature range 12–95°C. In the frequency region below 1 Kcycle/sec., the loss is predominently high both in the pure resin and the pure hardener and, interestingly, is very much reduced when the two are mixed to obtain a plasticized product; the loss is at a minimum when the percentage of epoxy is about 10 and increases appreciable on both sides of the figure. At frequencies above 1 Kcycle/sec., a relaxation type loss is obtained in the hardener and the plasticized samples; pure resin again shows a predominently high loss, the maximum for it at room temperature being above 100 Mcycles/sec.
Caractérisation de structures de fibres de cellulose régénérée par l'étude détaillée de leurs diagrammes de diffraction de rayons X et par divers traitements de gonflement. I. Étude détaillée des diagrammes de diffraction de rayons X de fibres et de feuilles d'hydrate de cellulose
Authors: Lefébvre S. G. , Ludé A. C. , Larticle M. 
Published: April 2003

AbstractThe authors have designed different experimental devices for the realization of strictly monochromatic diagrams of orientated samples, the fully automatic recording of numerous radial tracings thereof, and the careful analysis of their components. Because of the difficulty of interpretation of high tenacity rayons diagrams (due to poor resolution of peaks and the occurrence of cellulose IV) preliminary experiments have been carried out, with (a) particular examination of rayons containing no cellulose IV, (b) application of moderate swelling treatments causing a sharpening of diffraction peaks, (c) x‐ray examination of planar‐oriented cellulose samples giving “simplified” diagrams when irradiated under particular conditions. The information obtained from these experiments establishes the occurrence of a noncrystalline anisotropic part in regenerated cellulose fibers. There is a twofold orientation of the “amorphous” background in regenerated cellulose sheets. This is in favor of the occurrence of doubly anisotropic “pseudo‐amorphous” parts whose structure is of a paracrystalline type with superimposed dislocations. On the basis of different observations made on photometric tracings, a nonsubjective method is suggested for the individual evaluation of A0, A3 + A4 of cellulose II, (002) and (101 + 101) of cellulose IV, pseudo‐amorphous and amorphous components in regenerated cellulose diagrams. Individual orientation factors may be defined and measured for the components.
Some observations on the melting behavior of textile fibers. Part I. Core melting during hot‐stretching of nylon
Authors: Farrow B. , Simmens S. C. 
Published: April 2003

AbstractIt has been found that under certain conditions of heating, filaments of nylong melt from the center outwards. It has been established that this is associated with the presence of moisture in the filaments and that moisture lowers the melting point of the material. Well‐defined core effects and internal cavitation resulting in delustering of the filament may occur under conditions of shock heating. The melting point of nylon is raised by the presence of stress.
Ultrasonic degradation of sol rubber in solution
Authors: Chandra Sarswati , Roy‐Chowdhury Phanibhusan , Biswas A. B. 
Published: April 2003

AbstractSol rubber dissolved in three solvents—cyclohexane, petroleum ether (40‐60°C. fraction), and toluene—was degraded by ultrasonic waves, the degradation kinetics being followed by measuring spectrophotometrically the consumption of the free radical scavenger α,α′‐diphenyl‐β‐picryl hydrazyl. The kinetic data have been examined by the rate equations developed from two different approaches: one by Jellinek and the other by Ovenall. It has been observed that the number of bonds broken as a function of time can be fitted equally well by both equations in the initial stage, but as the time of degradation increases, especially when the number‐average degree of polymerization attains a value less than 3Pe/2, the rate can be described better by Jellinek's equation than that of Ovenall. The rate constants K and the final degree of polymerization for rubber are found to depend on the nature of the solvent.
Block copolymerization of unsaturated monomers and octamethylcyclotetrasiloxane
Authors: Morton Maurice , Rembaum A. A. , Bostick E. E. 
Published: April 2003

AbstractA study has been carried out on the preparation of block copolymers of styrene–dimethylsiloxane and isoprene–dimethylsiloxane. This has been accomplished by means of anionic polymerization, using potassium metal or potassium naphthalene as initiator, in tetrahydrofuran. Block copolymers of the ABA type were synthesized by first preparing the polystyrene or polyisoprene dianion, followed by polymerization of the octamethylcyclotetrasiloxane. Proof of the presence of these block copolymers was obtained from their solubility behavior and from the ability of the isoprene–siloxane polymers to undergo vulcanization by sulfur. The chain length of the polymeric blocks could be controlled in a predictable fashion, leading to a central segment (B) of polystyrene or polyisoprene, having a narrow molecular weight distribution, and two end segments (A) of polydimethylsiloxane, having a most probable distribution. The reverse type of block copolymer was not possible due to the inability of the siloxane to initiate styrene or isoprene polymerization.
Oxidation of cellulose microfibril segments by alkaline silver nitrate and its relation to the fine structure of cellulose
Authors: Colvin J. Ross 
Published: April 2003

AbstractThe oxidation by alkaline silver nitrate of segments (ca 0.1 μ long) of cellulose microfibrils from Avena coleoptiles, ramie, bacteria, and Valonia has been followed by electron microscopy. For comparison, chitin microfibrils have been oxidized by the same reagent and observed by the same method. Oxidation proceeds equally at both ends of the segments, as judged by the rate of deposition of colloidal silver. As a consequence of oxidation, dissolution of the ordered array of 1→4β‐polyglucosan chains (or poly‐N‐acetylglucosamine chains) takes place rapidly from both ends, due to Coulomb repulsion between ionized carboxyl groups and/or electrostriction of water molecules about the same groups. The observations are consistent with the assumption that the neighboring chains run in opposite directions in the cellulose microfibril (i.e., with the Meyer‐Misch antiparallel postulate). They are not in agreement with expectations based upon the parallel arrangement.
Determination of diffusion rates in swelling systems
Authors: Watt I. C. 
Published: April 2003

AbstractA new method of measuring diffusion coefficients of ethyl alcohol in keratin is described. Ethyl alcohol, which is retained in keratin on desorption by evacuation, is released by swelling the keratin with water vapor. The essential measurement is the loss of weight of the keratin as the ethyl alcohol diffuses out after the absorption of water. Values of the diffusion coefficients at 35°C. are given for a range of volume swelling of keratin where it is not possible to obtain the data by absorption or permeation measurements. The change of diffusion coefficient with swelling is in agreement with values obtained by absorption at lower and higher levels of swelling. The method should have general applicability to many polymer sorption systems where swelling occurs.
Dielectric behavior of curing phenolic‐formal resins
Authors: Van Beek L. K. H. 
Published: April 2003

AbstractDielectric properties of phenolic‐formal resins are studied between 0.06 and 300 kHz. The resins are prepared from novolac and 1,3‐dioxalane with a strong acid as catalyst. The high dielectric losses are attributed to proton jumps felicitated by water molecules which are produced in the curing reaction. The activation energy of the dielectric relaxation is 0.77 e.v. Curing often continues for weeks after preparation, which is reflected by a gradual increase of the frequency of maximum loss. Drying the samples causes the loss maximum to return to lower frequencies.
Study of the structure of polymers by infrared spectra
Authors: Vol'kenshtein M. V. , Volchek B. Z. , Gotlib Yu. Ya. , Nikitin V. N. 
Published: April 2003

AbstractIn this review a short outline of the results of the application of IR‐spectroscopy to the study of polymer physics is summarized. Questions of rotational isomerism, mechanical deformation of polymers, crystallization, intramolecular order, and microtacticity determination are discussed. Details are given on the authors' data concerning polypropylene, 1,4‐trans‐polybutadiene, poly(methyl methacrylate), and cellulose triacetate, and also data on calculations of spectra for different conformations of poly(vinyl chloride), poly(vinyl bromide), and poly(ethylene terephthalate).
Monolayers of linear poly(vinyl benzoate) and its mixtures with stearic acid
Authors: Beredjick Nicky 
Published: April 2003

AbstractMonomolecular films of linear poly(vinyl benzoate) (PVBz) and of mixtures of linear PVBz and stearic acid, show properties similar to branched PVBz and its mixtures with stearic acid. Nuclear magnetic resonance of linear and branched PVBz show no phenyl‐hydrogen splitting, chemical shift, or other differences in relative peak positions. These results are consistent with the structure of PVBz as derived from general mechanistic considerations. The unusual monolayer properties of this polymer may be attributed to superior contiguous alignment of aromatic rings and tighter packing, but not to branching.
Tack in urethane elastomers
Authors: Boenig H. V. , Miller C. B. , Shottafer J. E. 
Published: April 2003

AbstractThe phenomenon of tack has been studied in urethane‐urea elastomers prepared from polyether or polyester prepolymers and 4,4′‐methylenebis(2‐chloroaniline). It is shown that tack at zero elongation is attained only in polymers in which the flexible chains, i.e., polyesters or polyethers, contain 50 chain links or more. This coincides with the requirements for the Gaussian vector function in elastomers. The results suggest that, in the absence of flexible chain ends in these polymers, tack is solely contributed by the flexible segments along the polymer chains, while the rigid blocks in the chains do not participate in the formation of tack.
Polymers suitable for increasing the viscosity of formic acid: Application to the printing of wool with reactive dyes
Authors: Harrap B. S. , Rosman R. E. , Solomon D. H. 
Published: April 2003

AbstractA study has been made of the properties of formic acid solutions of several polymers in relation to their usefulness as thickening agents for printing pastes composed of reactive dyes dissolved in formic acid. Polybases effectively increase the viscosity of formic acid to a satisfactory level but because of their ionization in formic acid, they inhibit the uptake of dye on wool due to the “salt effect” previously described. Incorporation of styrene with the base into a copolymer dilutes the salt effect but not sufficiently to be of practical importance. It was found that high molecular weight poly(ethylene glycol) and several natural carbohydrate gums effectively increased the viscosity without affecting the dye uptake. Moreover, contrary to their behavior in aqueous solutions, these natural gums did not react with the reactive dyes in formic acid solution. It is suggested that these dyes do not react with wool itself in formic acid solution, but reaction takes place only after the formic acid has been removed by washing.
Nonlinear dynamic behavior of plastics
Authors: Sharma M. G. , Sen J. K. 
Published: April 2003

AbstractThe dynamic behavior at low frequencies of Penton (chlorinated polyether) which displays nonlinear response is described in terms of a free energy function and a dissipated energy function. The variation of the energy functions with frequency and magnitude of stress is determined experimentally from hysteresis tests. The dynamic properties of the material are expressed in terms of storage and loss modulus functions. In addition the dynamic behavior of the material at low frequencies is predicted from uniaxial static creep properties, using a modified superposition principle.
Fracture surface work measurements on glassy polymers by a cleavage technique. I. Effects of temperature
Authors: Broutman L. J. , McGarry F. J. 
Published: April 2003

AbstractIt has recently been postulated that viscous flow or plastic deformation occurs near the tip of an advancing crack in glassy amorphous polymers such as Plexiglas, and this results in molecular orientation of the fracture surface. The evidence for this has been the appearance of colors on fresh fracture surfaces of Plexiglas and the extremely high measured surface work which is 1000 times greater than the theoretical surface energy. The surface energy of a solid is defined as the amount of energy required to create unit area of surface in the material by separating two planes each of half a unit area in extent, and the measured surface work of a polymer may also include any irreversible work which occurred during the fracture process. In the present investigation a cleavage test has been empolyed to measure the surface work of glassy polymers and to measure the effects of temperature on the surface work. A reproducible procedure has been developed to measure the surface work of cracks which propagate continuously and for cracks which propagate in a stick‐slip fashion. The measured surface work of Plexiglas II is 1.2 × 102 erg/cm.2, and the value for a typical polystyrene is 4 × 105 erg/cm.2, compared to a theoretical estimate of 450 erg/cm.2. The surface work varies with temperature over the range of −40 to 80°C. The surface work of Plexiglas II and polystyrene decrease with increasing temperature. Colors have been seen on the Plexiglas fracture surfaces over the entire temperature range, and the fracture surface changes from rough to mirror‐smooth at elevated temperatures. The inherent flaw size of the polymers, from Griffith's equation, also varies with temperature and is thought to be related to the crazing behavior of the polymer. At 23°C. the flaw size for polystyrene is 0.05 in. and for Plexiglas II, 0.002 in.
Application of differential thermal analysis to polyethylene blends
Authors: Stafford Bill B. 
Published: April 2003

AbstractThe analytical application of differential thermal analysis (DTA) for the identification and evaluation of a number of polyethylene blends is described. New DTA data are presented for hompolymer blends of low and intermediate density polyethylenes and low and high density polyethylenes whose degrees of branching are sufficiently different. The concentration by weight of each of the crystalline components in the blend is determined from DTA thermograms by the peak area method and the melting point‐density method. The density of polyethylenes and polyethylene blends is determined with the use of density gradient columns.
Specific heat of wool in the temperature range −50 to 100°C
Authors: Haly A. R. , Abu‐Isa I. , Dole Malcolm 
Published: April 2003

AbstractThe specific heat of wool containing 2.6, 2.9, and 8.9 g. of water per 100 g. 01 dry wool has been measured over the temperature range −50 to 100°C. All of the wool samples showed an approximately linear increase of cp, with temperature, but small increments appeared at −30, 20, 50, and 70°C. With increasing water content at any one temperature the specific heat increased. The specific heat of the sorbed water seemed to be more nearly like that of ice than of liquid water; if the sorbed water is assumed to have the specific heat of ice a t all compositions and temperatures, an apparent specific heat of the wool can be calculated. With increasing water content the apparent specific heat of the wool approaches that of the synthetic polymer, nylon 6.
Transient permeation of organic vapors through polymer membranes
Authors: Meares Patrick 
Published: April 2003

AbstractA method of analyzing permeation data has been developed which permits the diffusion coefficient D, its variation with concentration, and the solubility coefficient to be determined from a single experiment on the permeation of a vapor through a membrane when diffusion is known to be Fickian. There is evidence that in the range from the glass temperature Tg to (Tg + 20°C.) the diffusion of an organic vapor into a polymer is not always Fickian. In such a case a single permeation experiment gives the limiting value of D at zero vapor concentration. If the sorption isotherm is determined, two or three permeation experiments give sufficient information to characterize the concentration dependence of D and to predict a “Fickian time lag.” The difference between the observed and the predicted time lag is the mean relaxation time of the time‐dependent factors in the non‐Fickian permeation. When there is a transient period of rapid permeation at the beginning of an experiment a plot of permeation rate against logarithmic time permits another relaxation time to be defined. By comparing these relaxation times with the mechanical characteristics of the polymer the time‐dependent mechanisms of permeation may be identified.
Factors affecting the solution properties of cellulose acetate
Authors: Neal J. L. 
Published: April 2003

AbstractAbsorbance measurements on concentrated solutions of cellulose 2 1/2‐acetates in acetone show that the apparent absorbance is almost entirely due to turbidity. The size of the scattering particles is comparable with the wavelength of light. Sedimentable fractions are responsible for the anomalous viscosity of concentrated solutions of cellulose acetates as well as for their turbidity. These sedimentable fractions are enriched in xylan and mannan acetate. Solubility differences found for sediments rich in either xylan or mannan acetate, and extraction experiments with polar and nonpolar solvents revealed that more polar impurities, such as xylan acetates, are responsible for turbidity, while less polar impurities, such as mannan acetates, are responsible for false viscosity. A hypothesis based on solvent interaction and polymer incompatibility has been advanced to coordinate these and earlier findings.
The photooxidation of polymers. IV. A note on the coloration of polystyrene
Authors: Grassie N. , Weir N. A. 
Published: April 2003

AbstractYellow coloration develops in polystyrene under 2537 A. radiation a t comparable rates whether or not oxygen is present. Thus the commonly accepted view that coloration is a manifestation of oxidation is wrong. The coloration increases in intensity with time but does not move toward the red end of the spectrum, behavior which is typical of poly(vinyl chloride), polyacrylonitrile, etc., and which is due to the development of long conjugation sequences. It is suggested that the color in polystyrene is due to conjugated carbon–carbon unsaturation in the polystyrene backbone but that the lack of mobility of the molecules within the rigid polymer films prevents long sequences of double bonds becoming coplanar and color consequently moving through the spectrum. The rapid darkening of irradiated polymer which occurs on melting is probably due to relaxation of this rigidity allowing coplanarity of longer sequences.
Cold water‐soluble films from cyanoethylated polyvinyl alcohol
Authors: Roth Roy W. , Patella Lawrence J. , Williams Bernard L. 
Published: April 2003

AbstractThe cyanoethylation of polyvinyl alcohol and the merits of using NaCN as the catallyst are discussed. The application of cyanoethylated PVA to cold water‐soluble films is specifically discussed. The use of NaOH catalysis was found to lead to nitrile hydrolysis which resulted in humidity‐susceptible films. By using NaCN catalysis, it was found that the reaction temperature and per cent solids could be increased resulting in a decrease in undersirable by‐product formation. It was found that films could be cast from cyanoethylated PVA with a degree of cyanoethylation between 5 and 10 mole‐% which were readily soluble in cold water and which had physical properties very similar to several commercial water‐soluble films.