bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation‐induced solid‐state polymerization in binary systems. VII. Polymerization in solid–liquid equilibrium phase containing long‐chain compounds
Authors: Kaetsu Isao , Ito Akihiko , Hayashi Koichiro 
Published: April 2003

AbstractThe radiation‐induced polymerization of binary systems consisting of vinyl monomers (mainly methyl methacrylate) and various long‐chain compounds in solid–liquid equilibrium state has been studied. Phase diagrams of these systems showed that all systems containing long‐chain compounds form a complete crystalline phase at temperatures below the solidus line. It was found that remarkable acceleration of the polymerization occurred in the solid–liquid equilibrium state. The long‐chain compounds are classified into three groups according to the acceleration effect. The group including paraffin, long‐chain esters, and cetyl alcohol exerted the largest acceleration effect over wide temperature regions at which the solid–liquid equilibrium exists. Maximum polymerization rate was observed at temperatures below the melting point in the presence of long‐chain compounds of the above‐mentioned group. It was observed in this case that the long‐chain compounds crystallized to form very fine colloidal particles and the system was soft and waxy in the solid–liquid equilibrium state. The acceleration of the polymerization in the binary system consisting of a vinyl monomer and a compound having no long‐chain substituents or in the homogeneous solution consisting of monomer and viscous solvent were far less than that in the presence of long‐chain compounds. It is suggested that the effect can be attributed to the effect of a special reaction matrix favorable to polymerization in the solid–liquid equilibrium.
Melting and crystallization behavior of poly(tetrafluoroethylene). New method for molecular weight measurement of poly(tetrafluoroethylene) using a differential scanning calorimeter
Authors: Suwa Takeshi , Takehisa Masaaki , Machi Sueo 
Published: April 2003

AbstractMelting and crystallization behavior of virgin polytetrafluoroethylene have been studied using a differential scanning calorimeter. Following quantitative relationship was found between number average molecular weight of polytetrafluoroethylene and the heat of crystallization in the molecular weight range of 5.2 × 105 to 4.5 × 107: M̄n = 2.1 × 1010 ΔHc−5.16, where M̄n is number average molecular weight and ΔHc is the heat of crystallization in cal/g. The heat of crystallization is independent of cooling rate ranging from 4 to 32°C/min. This relationship provides a simple rapid and reliable method for measuring the molecular weight of polytetrafluoroethylene.
Viscoelastic and friction characteristics of polydiene, and butadiene–styrene copolymer tread compounds with application to tire dynamics
Authors: White James L. , Lin Yih Ming 
Published: April 2003

AbstractAn experimental study of the linear viscoelastic and friction properties of passenger tire tread compounds containing realistic black and oil contents and several different types of elastomers including cis‐polyisoprene, cis‐polybutadiene, emulsion polymerized polybutadiene, and three emulsion polymerized butadiene—styrene copolymers (SBR's) has been carried out. E′ (ω) and tan δ were determined as a function of frequency and temperature. At any specific frequency and temperature, tan δ was an increasing function of Tg or a decreasing function of T − Tg. When the tan δ–frequency data were plotted at the same T − Tg, all of the treads based upon emulsion‐polymerized butadiene polymers yielded nearly the same curve. Wet coefficients of friction of the tread compounds correlated with both tan δ and T − Tg supporting the idea that lubricated friction is largely due to hysteresis. The correlation among the butadiene—styrene polymers was much better than with the natural rubber, which exhibits a lower tan δ and a higher wet coefficient of friction than an SBR of the same Tg. The experimental results are used to investigate the heat buildup and skid properties of tires containing these tread compounds.
Characterization of drag reduction and degradation effects in the turbulent pipe flow of dilute polymer solutions
Authors: Ting R. Y. , Little R. C. 
Published: April 2003

AbstractTurbulent drag reduction data were obtained at Re = 9000 in a 0.62‐cm‐I.D. pipe for five Polyox compounds covering a wide range of molecular weights. The concentration dependence of drag reduction was shown to obey an improved form of Virk's drag reduction equation, which was previously applied only to flows in capillary tubes. The efficiency of the drag‐reducing polymer additives on a unit concentration basis at infinite dilution was determined by using a characteristic parameter, DRm/[c], for each compound. A linear relationship was found to exist between this parameter and polymer molecular weight. The polymer degradation data were analyzed through use of a variable related to the dissipated energy in the wall region. The polymer molecular weight was found to decrease as a hyperbolic function of the dissipated energy function. By examining the change of molecular weight with respect to this function, a degradation index characteristic of the entire Polyox polymer family was established. This index may be of general application and provide a method by which the shear stability of various species of drag‐reducing polymers may be meaningfully compared.
Applications of gel permeation chromatography. III. Formulation
Authors: Schrager Morton 
Published: April 2003

AbstractThis paper describes a general theory for the optimization of multicomponent blending to achieve a desired chromatographic distribution. A procedure for compound blending is also discussed, where optimum replication of both the chromatographic spectra and a second independent parameter can be achieved. Lastly, this theory is applied in a hypothetical example.
Dynamic mechanical properties of some epoxy matrix composites
Authors: Jenness J. R. , Kline D. E. 
Published: April 2003

AbstractDynamic mechanical properties of some epoxy matrix composites have been studied, comparing experimental data with theoretical models. The matrix in all composite samples was Shell Epon 828, a diglycidyl ether of bisphenol A, cured with meta‐phenylenediamine. Fibrous composite samples were made with glass and graphite fibers. Particulate composite samples were made with glass microspheres, atomized aluminum, powdered silica, alumina, asbestos, mica, carbon black, and graphite. The dynamic elastic modulus and damping of these samples were measured at temperatures between 85° and 345°K by a free‐free flexural resonance technique. The dynamic modulus of parallel fiber composites follows the linear rule of mixtures for low fiber volume fractions; deviations from linearity at higher volume fractions appear to be due to defects caused by the sample fabrication technique. Dynamic moduli of the particulate composites conform, within experimental error, to the static modulus theory of Wu up to filler volume fractions of 0.35 to 0.40. Deviations from Wu's theory at higher volume fractions may be due to agglomeration of filler particles. The damping of particulate composites with quasi‐spherical filler particles appears to follow the rule of mixtures. In particulate composites with needle‐ and flake‐type fillers, and in fibrous composites, the fillers are more highly stressed; with more of the strain energy in the low‐damping fillers, overall damping is reduced. Damping greater than that attributable to the matrix and filler may be due to slippage at the interface between them. In addition to supporting Wu's theory of the elastic modulus of a particulate composite, this study demonstrates the utility of the nondestructive free‐free flexural resonance techniques for obtaining a large body of reliable data in a short time from relatively few small samples. This greatly facilitates the experimental testing of theoretical models and the evaluation of fillers, matrix materials, and fabrication techniques.
Mechanism for the action of tackifying resins in pressure‐sensitive adhesives
Authors: Sherriff M. , Knibbs R. W. , Langley P. G. 
Published: April 2003

AbstractIn a study of pressure‐sensitive adhesives prepared from mixtures of natural rubber and three different tackifying resins, it was shown that a tackifying resin may form either one‐ or two‐phase systems with natural rubber. Measurements of the viscoelastic properties of the adhesives show that the effect of tackifying resins is to modify the viscoelastic properties so that the adhesive performance in bonding and unbonding is improved. It is suggested that a two‐phase system is not necessary for good tack, and a theory based on a two‐phase system cannot adequately explain the rate dependence of tack tests. Tack measured by the probe test is shown to be dependent upon a balance between the viscoelastic properties and the transition temperature of the adhesives. This theory is used to explain the effect of contact time, withdrawal speed, and resin softening point on the tack of adhesives.
Nonlinear viscoelastic behavior of plasticized poly(vinyl chloride)
Authors: Dehoff P. H. , Chakrabarti M. K. 
Published: April 2003

AbstractThis paper shows how an empirical nonlinear creep relation suggested by Leaderman might be justified on the basis of an approximate nonlinear viscoelastic constitutive equation. In addition, experimental evidence is presented which tends to support the proposed theory.
Mechanism of the benzophenone‐sensitized photodegradation of polypropylene
Authors: Harper D. J. , McKellar J. F. 
Published: April 2003

AbstractThe photodegradation of polypropylene sensitized by benzophenone has been studied under accelerated light‐aging conditions using a Xenotest 150. Degradation of the polymer and consumption of the benzophenone was monitored by infrared spectroscopy. The results indicate that hydrogen stom abstraction from the polymer, by photo‐excited benzophenone, is the major primary process in the mechanism of sensitized photodegradation.
Nonlinear constrained optimization of filled polyesters
Authors: Fricke A. L. , Natarajan V. K. , Caskey J. A. , Kutat H. L. 
Published: April 2003

AbstractAn efficient method for optimization of a formulation problem subject to nonlinear constraints was demonstrated. Specifically, a nine‐variable polyester‐filler system was investigated experimentally. The investigation included selection of an efficient experimental design, regression analysis, and study of optimization methods. Recommended procedures are reported, along with examples and discussion of several typical applications.
Etude PAR spectroscopie de la deshydratation de dérivés de l'alcool polyvinylique: Mise en evidence d'une répartition séquentielle des substituants
Authors: Moigne J. Le , Gramain Ph. 
Published: April 2003

AbstractThe dehydration of sulfopropylic and alkyl derivatives of poly(vinyl alcohol), with varying degrees of substitution, was observed using ultraviolet and visible spectroscopy. The dehydration reactions were carried out in a KHSO4/heptane system kept under nitrogen at 100°C. Spectroscopic results show that definite sequences of conjugated double bonds are formed. The distribution of the number and length of these conjugated sequences was determined and compared with the theoretical values obtained assuming statistical distribution of the substituents. From this work it is concluded that: (1) the grafting of propane‐sultone onto poly(vinylalcohol) molecules does not follow a random, statistical pattern, rather the reaction is sequential, i.e., of a “zip” type. The product molecules contain blocks of sulfopropylic‐substituted vinyl alcohol groups. (2) The grafting of alkyl groups onto the poly(vinyl alcohol) molecules also occurs in a sequential manner. Results obtained show that the polymer chains contain at least two unreacted hydroxyl functions between each substituent alkyl group; this is in agreement with x‐ray studies of these derivates. Further evidence of an ordered distribution of the substituents along the polymer chain is given by the heterogeneity in the compositions of the substituted polymers. The difference in the observed structures of the two substituted polymers demonstrates the importance of the nature of the substituents in determining the reaction mechanism. It is concluded that the structural differences observed are due to differences in the solubility of the sulfopropylic and alkyl reactants in the original reaction medium, and the hydrophilic and hydrophobic character of the sulfopropylic and alkyl substituents in the polymer.
On the thermal degradation of poly(vinyl chloride). I. An apparatus for investigation of early stages of thermal degradation
Authors: Abbås Kent B. , Sörvik Erling M. 
Published: April 2003

AbstractA dehydrochlorination apparatus is described for studies of the early stages of the thermal degradation of poly(vinyl chloride) (PVC), combining good reproducibility, high accuracy, and a low detection limit. The evolved hydrogen chloride is absorbed in water and the electrical conductivity is continuously recorded. Measurements of the rate of dehydrochlorination repeated over an extended period of time showed a standard deviation of 2% of the mean value. The activation energies for the dehydrochlorination in nitrogen for two commercial suspension‐polymerized samples were found to be 27.9 ± 1.5 and 26.2 ± 0.6 kcal/mole.
Preparation and copolymerization of polyvalent metal salts of ethyleneglycol–methacrylate–maleate
Authors: Matsuda Hideaki , Kanaoka Kunio 
Published: April 2003

AbstractPreparation of polyvalent metal salts of ethyleneglycol–methacrylate–maleate (EMM) was investigated by the reaction of Na salt of EMM and chlorides of polyvalent metals such as Al3+, Cr3+, Fe3+, Ni2+, Co2−, and Cu2+. It was found that, among the metal salts obtained, the Cr salt could be obtained in the form of (EMM)2Cr(OH) in high purity, where EMM means EMM residue,

Then, (EMM)2Cr(OH) was copolymerized with styrene, MMA, and hydroxyethyl methacrylate. In the copolymerization, the rates of copolymerization increased markedly as the concentration of (EMM)2Cr(OH) increased. As for the physical properties of the copolymers obtained, Rockwell hardness and compressive strength can be improved by introducing (EMM)2Cr(OH) into the polymers, and HDT, tensile, and flexural strengths can also be improved by selecting the most suitable concentration of (EMM)2Cr(OH) according to the species of vinyl monomer. Further, TGA and boiling water resistance of the copolymers are also discussed.
Crystallization kinetics of poly‐ε‐caprolactone from poly‐ε‐caprolactone/poly(vinyl chloride) solutions
Authors: Robeson Lloyd M. 
Published: April 2003

AbstractThe polymer–polymer solution of poly(vinyl chloride) and poly‐ε‐caprolactone yields an excellent system for studying the crystallization kinetics of a crystallizable component from a polymer–polymer solution. Unlike previous studies of isotactic–atactic polystyrene solutions for which the glass transition temperature is invariant with composition, this system exhibits a marked dependence of Tg on the composition. The experimental data dE⅓(modulus)/dt (psi⅓/min) were obtained over a composition range of 40 to 70 wt‐% poly‐ε‐caprolactone. With the appropriate modification of the spherulitic growth rate equation, the expression

approximated a reasonable fit of the experimental data. This demonstrates a marked dependence of the crystallization rate on concentration. Secondary observations of this investigation show a slower crystallization rate for high molecular weight poly‐ε‐caprolactone and a slow secondary crystallization step. Both homopolymer poly‐ε‐caprolactone and poly‐ε‐caprolactone in the poly‐ε‐caprolactone/poly(vinyl chloride) solution show a slow (relative to the nucleation‐controlled step) crystallization stage considered to involve a slow diffusion mechanism.
Molecular weight decrease in the early pyrolysis of crystalline and amorphous cellulose
Authors: Broido A. , Javier‐Son A. C. , Ouano A. C. , Barrall Edward M. 
Published: April 2003

AbstractSamples of ordinary “ash‐free” cellulose papers and similar samples decrystallized by swelling in liquid ammonia were pyrolyzed in vacuo to a weight loss ranging from <0.1% to nearly 20%. The samples were then nitrated and their molecular weight distributions determined by gel permeation chromatography. When weight loss reached 1%, both the ordinary and the ammonia‐swelled celluloses showed a large drop in average degree of polymerization (D.P.). However, the ordinary cellulose showed this sharp drop long before there was any measurable weight loss; the ammonia‐swelled cellulose changed D.P. only gradually in the early stages. Further, x‐ray diffraction measurements showed that by the time the D.P. of the ammonia‐swelled cellulose had dropped appreciably, the material had developed a significant crystalline pattern. These results support the suggestion that initial rupture of the cellulose molecule occurs at strain points at the crystalline–amorphous boundaries.
On the dynamics of melt spinning
Authors: Cernia E. , Conti W. 
Published: April 2003

AbstractThe dynamics of melt spinning was examined in the case of a Lethersich liquid taking also into account a phenomenologic way as well the transition zone between shear and elongational flow. The shape of the fluid jet was measured under many spinning conditions; the filament temperature and the fluid viscosity were then calculated. The experimental viscosity temperature relationship was compared with the W. L. F. equation, and the comparison makes it clear that the Newtonian model is not adequate whereas all the experimental evidence is in qualitative accordiance with the proposed model.
Preparation of fine powdery copolymer with crosslinkage and monoalkyl maleate unit
Authors: Mizutani Yukio , Matsuoka Seishiro , Iwasaki Masatoshi , Miyazaki Yoshimichi 
Published: April 2003

AbstractIn order to prepare fine powdery and crosslinked copolymer as a foaming agent and a modifier for polypropylene, the following processes were investigated: (1) polymerization of monoalkyl maleate–styrene–divinylbenzene; (2) polymerization of monoalkyl maleate–maleic anhydride–styrene–divinylbenzene; (3) polymerization of maleic anhydride–styrene–divinylbenzene and esterification of the copolymer with methanol, and (4) polymerization of maleic anhydride–styrene–divinylbenzene in the presence of methanol. The thermal treatment of copolymer thus obtained and the foaming ability for polypropylene were then investigated.
Reverse osmosis separation of hydrocarbons in aqueous solutions using porous cellulose acetate membranes
Authors: Matsuura Takeshi , Sourirajan S. 
Published: April 2003

AbstractA physicochemical parameter, represented by the symbol Σs*, based on molar solubility in water and molar attraction constants of Small, has been developed to express quantitatively the relative hydrophobicity, or nonpolar character, of the hydrocarbon molecule. The value of Σs* can be calculated for a hydrocarbon from its chemical structure. The scale of Σs* is consistent within each group of aromatic, cyclic, and noncyclic hydrocarbons. Reverse osmosis data have been obtained at 250 psig for single‐solute aqueous feed solution systems involving low concentrations of 39 different hydrocarbons (including 13 aromatics, 10 cyclic, and 16 noncyclic compounds) and several samples of cellulose acetate membranes of different surface porosities. The effect of operating pressure on membrane performance has also been studied for two aromatic hydrocarbon solutes. The values of Σs* for the solutes used were in the range of 425 to 924 for aromatic hydrocarbons, 521 to 931 for cyclic hydrocarbons, and 369 to 960 for noncyclic hydrocarbons. The reverse osmosis data have been correlated with Σs* for each group of hydrocarbons studied. In all cases, positive solute separations were obtained, and the ratio [PR]/[PWP] was less than 1. With respect to each film, solute separation increased with increase in Σs*, and decreased with increase in operating pressure. Also, solute separation decreased in the order aromatic hydrocarbon > cyclic hydrocarbon > noncyclic hydrocarbon at any given value of Σs*. At a given operating pressure, for low values of Σs* (∼500 or less) solute separation increased with progressive decrease in average pore size on the membrane surface. For high values of Σs* (∼800 or more), solute separation initially increased with decrease in average pore size, then passed through a maximum and minimum with further decrease in average pore size, and again increased with still further decrease in average pore size. The results are discussed on the basis of preferential sorption of solute at the membrane–solution interface under the experimental conditions studied.
The formation of translucent cold‐drawn polypropylene
Authors: Lee C. , Uhlmann D. R. 
Published: April 2003

AbstractThe behavior of quenched samples of polypropylene subjected to stress relax–reload cycles during cold drawing has been investigated as a function of quench severity and strain rate. Results obtained by cooling the propagating neck of a drawing sample are also discussed. A translucent cold‐drawn form of the polymer, characterized by a small microvoid content, is observed when the propagating neck boundary is cooled or when stress relax–reload cycles are carried out at sufficiently high strain rates. A small mobility of the chains relative to the local strain rate is postulated as necessary for the formation of the translucent material.
Diffusion in polyelectrolyte solutions
Authors: Griskey Richard G. , Sedahmed G. H. 
Published: April 2003

AbstractDiffusion in polyelectrolyte solutions was studied. The mass transfer was determined by an electrochemical technique which involved transport from the fluid to the tube wall. It was found that diffusion behavior depended on the ionic nature of the diffusing species. Neutral molecules showed an increase in diffusion coefficients. This was apparently due to both solvation of solvent molecules and extension of polymer molecules. Ionic diffusing species showed a decrease in diffusion coefficients. The greater the ionic strength, the greater the decrease. The effect was most likely due to ionic interaction with the polyelectrolyte molecules.
Degradation of thin films of a fluoropolymer
Authors: Tompkins Harland G. 
Published: April 2003

Abstract1H‐1H‐Pentadecafluorooctyl methacrylate, a fluoropolymer, is used as a barrier coating to control spreading of thin liquid films, notably silicone oil. Using infrared spectroscopy and thermogravimetric analysis, this work describes the thermal degradation of thin films of this fluoropolymer. The conclusions are that the degradation is a two‐stage, thermal bond‐breaking phenomenon which does not required an additional reactant such as oxygen or water vapor. Rate constant data are presented for both stages of the degradation.
Isothermal transitions of a thermosetting system
Authors: Gillham J. K. , Benci J. A. , Noshay A. 
Published: April 2003

AbstractA study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures. These are Tg∞ (the maximum glass transition temperature of the thermoset system) and Tgg (the glass transition temperature of the material at its gel point). Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur: if Tcure > Tg∞, only gelation is observed; if Tg∞ > Tcure > Tgg, both gelation and vitrification are observed; if Tcure < Tgg, only vitrification is observed. Tgg corresponds to the isothermal cure temperature at which gelation and vitrification occur simultaneously. Methods for determining the time to gel and the time to vitrify, and also Tg∞ and Tgg, have been developed. The time to gel obeyed the Arrhenius relationship, whereas the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of Tg∞ and Tgg.