bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cocrystallization and polymer miscibility
Authors: Starkweather Howard W. 
Published: April 2003

AbstractLow‐density polyethylene was blended in various proportions with an ethylene/propylene/1,4‐hexadiene copolymer having an ethylene/propylene mole ratio of 4.5 and a low level of crystallinity. The DSC melting peak of polyethylene was decreased, the unit cell was expanded, and the spherulitic development was disturbed. The temperature of a dynamic mechanical loss peak varied smoothly with composition between the Tg of the copolymer and the β‐relaxation of the polyethylene, but the glass temperature of the copolymer measured by DSC was unchanged. These effects were all diminished when the ethylene/propylene ratio of the copolymer was reduced. Blends with highdensity polyethylene showed little depression of the melting point or change in crystal structure and much less effect on the dynamic mechanical behavior. However, the behavior of copolymers of ethylene with low levels of vinyl acetate or methyl methacrylate was similar to that of low‐density polyethylene. Therefore, the ability to cocrystallize is an important factor for limiting the tendency of nonpolar polymers to separate, thereby facilitating the preparation of blends with desirable combinations of properties.
New approach to aqueous gel permeation chromatography of nonderivatized cellulose
Authors: Bao Yen T. , Bose Arindam , Ladisch Michael R. , Tsao George T. 
Published: April 2003

AbstractA novel approach to the gel permeation chromatography (GPC) of nonderivatized cellulose is reported using Sepharose CL‐6B as the column packing material, 0.5N NaOH as the eluent, and cadoxen as the cellulose solvent. The traditional approach to GPC of cellulose has been to convert the cellulose to its nitrate thereby making it soluble in the solvent tetrahydrofuran. The circumvention of the need to derivatize the cellulose in the new system results in considerable saving of time. The new system gives good fractionation for cellulose. It also provides excellent separation of polystyrene sulfonate and dextran standards thereby making the system amenable to calibration. The effect of the particle size distribution of the column packing material on the efficiency of separation is discussed. Potential applications for this new method include studies on both acidic and enzymatic hydrolysis as well as fine structure of cellulose, starch, and other polymers capable of forming stable alkaline solutions.
Phosphorylation of cellulose: Effect of the reactivity of the starting polymer on the properties of the phosphorylated product
Authors: Zeronian S. H. , Adams S. , Alger K. , Lipska A. E. 
Published: April 2003

AbstractWhen cellulose is phosphorylated with phosphorus oxychloride, the reactivity of the cellulose, as well as reaction time and temperature, influences the relative amounts of phosphorylated and chlorinated product formed. The swelling ability of the phosphorylated product is affected by the pretreatment received by the cellulose (i.e., prior to phosphorylation) to change its reactivity. The thermal decomposition process of phosphorylated cellulose, as indicated by differential thermal analysis, is affected also by the pretreatment received by the cellulose.
Microphase separation and properties of urethane elastomers
Authors: Nierzwicki W. , Wysocka E. 
Published: April 2003

AbstractSeveral polyurethanes were prepared from poly(ethylene adipate)glycol, 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol, or 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane. Thermomechanical curves were determined for all investigated systems, and the glass transitions found thereof formed the basis of subsequent analysis. The analysis showed that the investigated systems belonged to those polyurethanes that can undergo microphase separation. It was also shown that the separation in the diamine‐extended elastomers was less sensitive to changes in chemical composition than in the diol‐extended systems. The diamine‐based polyurethanes were also closer to the ideal separation than the diol‐extended elastomers. Examinations of elastomers of varying amount of chemical crosslinking revealed a joint action of the crosslinking and microphase separation in determining mechanical properties of the systems. Together with swelling measurements, the examinations showed that optimum mechanical properties were obtained while keeping a very careful balance between these two factors.
Effects of fiber length on the tensile strength of epoxy/glass fiber and polyester/glass fiber composites
Authors: Miwa Minoru , Ohsawa Tadashi , Tahara Kenji 
Published: April 2003

AbstractIn discontinuous fiber‐reinforced composites, the shear strength at the fiber–matrix interface plays an important role in determining the reinforcing effect. In this paper, a method was devised to accurately determine this shear strength, taking the strength distribution of glass fiber into consideration. Calculated strength values based on the shear strenght obtained by the method were in better agreement with the experimental observations than those calculated by employing the shear strength obtained on the assumption that the fiber strength was uniform. The tensile strength of composites increases with increasing aspect ratio of the reinforcing fibers. This trend is almost the same regardless of the kind of matrix, the nature of interfacial treatment, and the environmental temperature. When composites are reinforced with random‐planar orientation of short glass fibers of 1.5 times the mean critical fiber length, the tensile strength of composite reaches about 90% of the theoretical strength of composites reinforced with continuous glass fiber. Reinforcing with glass fibers 5 times the critical length, the tensile strength reaches about 97% of theoretical. However, from a practical point of view, it is adequate to reinforce with short fibers of 1.5–2.0 times the mean critical fiber lenght.
On shift and resolution of relaxation maxima in two‐phase polymeric systems
Authors: Lipatov Yu. S. , Rosovitsky V. F. , Babich B. V. , Kvitka N. A. 
Published: April 2003

AbstractThe results of calculations of viscoelastic properties of filled polymers assuming “boundary layer” and the polymer matrix having their own and different glass transition temperatures are presented. The calculations have been made on the basis of the models in series and parallel coupling of viscoelastic bodies as well as Takayanagi's model. Using specified temperature, dependences of viscoelastic properties of the polymer and the “boundary layer” temperature dependences of the real part G′ of the complex shear modulus and tan δ for such a two‐phase system with varied differences in glass transition temperatures and concentration of the components were derived. The degree of maxima shift observed experimentally for the filled polymer owing to variation of properties of the “boundary layer” (its concentration and glass transition temperature) were evaluated. Conditions for the appearance of two maxima tan δ for the respective glass transtion temperatures of the polymer and “boundary layer” on the curves tan δ = f(T) were determined.
Morphology and fracture properties of pure and reinforced aluminum‐epoxy adhesive joints
Authors: Mijović Jovan 
Published: April 2003

AbstractSeveral types of nonreinforced and reinforced epoxy‐aluminum adhesive joints were prepared and investigated. High modulus carbon fibers and hollow glass microspheres were used as reinforcement. The amount of curing agent, postcure time, adhesive thickness, and type and amount of reinforcement were varied throughout this study, and their effect on fracture energy was determined. Unstable crack propagation through the adhesive layer was observed. Nodular morphology typified all fracture surfaces of nonreinforced adhesive joints, indicating the existence of an inhomogeneous thermosetting network. Electron microscopic evidence was obtained for plastic flow in crack initiation and crack arrest regions. The nature of this plastic flow was discussed in terms of changes in the resin morphology.
Stabilization of poly(vinyl chloride). VI. Synergetic effects of aminopolycarboxylates or nitrogen‐containing agents with zinc stearate/calcium stearate soap
Authors: Iida Takeo , Gotō Kunio 
Published: April 2003

AbstractDiscoloration such as zinc burning was observed in aged poly(vinyl chloride) (PVC) compounded with synergetic soaps. This discoloration was caused by excessive formation of cool color‐producing π complexes formed between double bonds in polyene chain and zinc chloride or cadmium chloride produced from the corresponding metal soap. The appearance of excessive color of the π complexes was reduced by adding some masking agents into PVC admixed with synergetic soaps. In the present study differences in masking effects results by adding solid or an aqueous solution of aminopoly‐carboxylates such as glycine, ethylenediaminetetraacetates, and nitrilotriacetates to PVC stabilized with zinc stearate/calcium stearate synergetic soap. The mechanism of synergetic effect between nitrogen‐containing agents and synergetic soaps upon the stabilization of PVC is also investigated by colorimetry. The aqueous solution of aminopolycarboxylates exhibits a greater masking effect than the solid. The masking effect of aminopolycarboxylates depends on the ease with which they are fnely dispersed into PVC. Colorimetry indicated that the masking effect of aminopolycarboxylates and other nitrogen‐containing agents depends on forming the colorless complex compound with the excessive cool color‐producing metal chlorides.
Structure and properties of acrylonitrile‐[(2‐methacryloyloxy)alkoxy]trimethyl silane copolymers
Authors: Bajaj P. , Gupta D. C. , Gupta A. K. 
Published: April 2003

AbstractDielectric, x‐ray diffraction, density, thermomechanical, and thermogravimetric studies on polyacrylonitrile (PAN), poly[acrylonitrile‐(2 methacryloyloxy)ethoxytrimethylsilane] [poly(AN‐2MAETMS)], and poly[acrylonitrile‐(2 methacryloyloxy)propoxytrimethylsilene] [poly(AN‐2MAPTMS)] copolymers have been carried out for investigating their structure. The glass transition temperature as indicated from the dielectric and thermomechanical analysis data are lower for the copolymers as compared to PAN. Crystallinity is influenced by the introduction of the silylated acrylic comonomer units but the crystalline lattice remains similar to that of PAN. The changes obseved in the various properties of these coplymers clearly suggest a more closely packed structure of poly(AN‐2MAETMS) than poly(AN‐2MAPTMS), and the uninterrupted PAN sequences are longer in the former. Thermal stability of copolymers has also been investigated.
Investigation on the synthesis and characterization of rare earth metal‐containing polymers. II. Fluorescence properties of Eu3+–polymer complexes containing β‐diketone ligand
Authors: Ueba Y. , Banks E. , Okamoto Y. 
Published: April 2003

AbstractEuropium(III) chelates of dibenzoylmethane (DBM) (1) and β‐diketone‐containing polymers, i.e., poly(p‐benzoylacetylstyrene) (2) and poly(aryl β‐diketone) (3), were prepared. In the polymer 2 the β‐diketone moiety is attached to the phenyl ring, and for polymer 3 the β‐diketone group is incorporated in the linear chain. The chelate structures were confirmed by measuring IR spectra, TGA, and DTA. The fluorescence emission intensity was measured on fine powder samples. For the composite samples of Eu(DBM)4 in polystyrene, the fluorescence intensity was found to increase linearly with increasing Eu content. However, for Eu coordination polymers, the intensity reached a maximum at Eu3+ content as small as 1 wt % and remained constant on further increasing the Eu3+ content. When the fluorescence intensities of Eu complexes were compared under the same conditions, namely, 1 wt % Eu, at which Eu–2 and Eu–3 show nearly maximum intensity, the order was found to be Eu–1 > Eu–2 > Eu–3. These phenomena were accounted for by the differences in the coordination number of the Eu complexes.
Kinetics and conversion monitoring in a RIM themoplastic polyurethane system
Authors: Steinle Edmund C. , Critchfield Frank E. , Castro José M. , Macosko Christopher W. 
Published: April 2003

AbstractKinetic data are reported for the fast polymerization of a thermoplastic polyurethane under conditions similar to that of commercial reaction injection molding (RIM). The components were a 2000 molecular weight polyester polyol, butanediol and 4,4′‐diphenylmethane diisocyanate. Three catalysts–dibutyltin dilaurate, phenyl mercuric propionate, and triethylenediamine–as well as uncatalyzed formulations were studied. Kinetic parameters were obtained by numerically fitting adiabatic temperature rise data with both second‐order and hyperbolic models. The hyperbolic model gave consistently better fits and is supported by mechanistic studies in the literature. Activation energies compare well to literature values. The uncatalyzed rate was found to be significant. The kinetic parameters obtained by this method are useful measures of catalyst performance in the RIM systems. Moreover, the models provide a conveient way to predict the extent of reaction during the production of parts by the RIM process. The shape of the reaction pathway (extent of reaction time) may be important in the development of physical properties of polymers produced by the RIM process. Physical properties for these samples compare favorably to those for a conventionally produced (batch) polyurethane of the same formulation.
Flammability resistance synergism in BPA polycarbonate–silicone block polymers
Authors: Kambour R. P. 
Published: April 2003

AbstractThe synergism in limiting oxygen index found in BPA carbonate–dimethylsiloxane block polymers (BPAC/DMS) is correlated with a rise in yield of pyrolytic char and an improvement in char oxidation resistance. These changes in turn are related to a peaking of fractional silicon retention in the char at a resin composition of 50 mole % DMS. This behavior, the fine dispersion of silicon in the char, and analyses of the pyrolysates suggest that an important feature of char formation in the block polymers is a polycondensation reaction between pyrolysis products from the two blocks. In addition to the role of chars in withholding fuel from the flame, they are thought to function effectively as thermal insulators.
Gas permeability of copolypeptide membranes composed of γ‐methyl L‐glutamate and γ‐benzyl L‐glutamate
Authors: Minoura Norihiko , Fujiwara Yukihiko , Nakagawa Tsutomu 
Published: April 2003

AbstractMembranes of copoly(γ‐methyl L‐glutamate, γ‐benzyl L‐glutamate) (PMBLG) as well as the related homopolymer membranes were prepared, and permeabilities of oxygen, nitrogen, argon, and carbon dioxide were measured in the 0–70°C temperature range. The values of permeability coefficients and solubility coefficients of the copolymers were smaller than those of permeability coefficients and solubility coefficients of the two homopolymers for every gas studied. The diffusion coefficients of the gases showed a minimum at around 25 mole % benzyl glutamate. The temperature at a maximum of tan δ spectra for the membranes showed a maximum at around 25 mole % benzyl glutamate. The Arrhenius plots of diffusion coefficients and solubility coefficients for PMBLG, which contained 50 and 71 mole % benzyl glutamate, showed a break at about 50 and 40°C, respectively. This permeation behavior is explained by assuming a unique interaction between methyl glutamate and benzyl glutamate side chains.
Effects of ionizing radiation on perfluorosulfonic acid ion‐exchange polymer
Authors: Balko E. N. , Chaklos J. T. 
Published: April 2003

AbstractThe effects of β and γ radiation on the Nafion perfluorinated ion‐exchange polymer have been examined and the radiolysis products have been identified. The polymer degrades by simple chain scission, and the rate of degradation is not affected by the state of polymer hydration of the nature of the ion which occupies an exchange site.
Delignification and degelation: Analogy in chemical kinetics
Authors: Yan Johnson F. , Johnson Donald C. 
Published: April 2003

AbstractStructurally and kinetically, chemical pulping can be treated as a degelation process. Kinetics derived from the empirical power law is rejected on the grounds that lignin is a polymer. Using an extended version of the Flory–Stockmayer theory and a kinetic expression derived by Whittle, the delignification kinetics is expressed in terms of opposing unimolecular–bimolecular reactions. The quantity replacing lignin concentration is the “extent of reaction” defined in the theory. Parameters used in this reaction are estimated, and the time dependence of the undissolved lignin fraction can be calculated. The calculated delignification curve is shown to be in good agreement with experimental results.
Copolymerization of styrene with acrylamide in an emulsifier‐free aqueous medium
Authors: Ohtsuka Yasuji , Kawaguchi Haruma , Sugi Yoshishige 
Published: April 2003

AbstractCopolymerization of styrene with acrylamide was carried out in an emulsifier‐free aqueous medium. The resulting latex contained an appreciable amount of acrylamide‐rich copolymer in the serum. The copolymerization course was divided into three stages on the basis of the main reaction locus. At first, acrylamide polymerized in preference to styrene in the aqueous phase. Water‐soluble growing radicals lost hydrophilicity rapidly and nucleated the particles. After particle formation, styrene polymerized exclusively in the particles until styrene droplets disappeared. The decrease in the concentration of residual styrene monomer caused growing radicals to keep the hydrophilicity for a long time, and polymerization of acrylamide was accelerated in the aqueous phase. Polymerizations at higher temperature and lower pH resulted in prolongation of the first stage of the polymerization, that is, preferential polymerization of acrylamide in the aqueous phase. An increase in the acrylamide fraction in monomer feed caused some decreases in the particle size and its uniformity.
Model networks of end‐linked polydimethylsiloxane chains. XII. Dependence of ultimate properties on dangling‐chain irregularities
Authors: Andrady A. L. , Llorente M. A. , Sharaf M. A. , Rahalkar R. R. , Mark J. E. , Sullivan J. L. , Yu C. U. , Falender J. R. 
Published: April 2003

AbstractElastomeric networks were prepared by end‐linking vinyl‐terminated polydimethylsiloxane (PDMS) chains having number‐average molecular weights of 11.3 × 103 g mol−1. The tetra‐functional end‐linking agent, Si[OSi(CH3)2H]4, was used in varying amounts smaller than that corresponding to a stoichiometric balance between its active hydrogen atoms and the chain vinyl groups. The number of dangling‐chain irregularities thus introduced into the networks was directly determined by iodometric titration for unreacted vinyl groups. The (unfilled) PDMS networks thus obtained were studied in elongation to their rupture points at 25°C (a temperature sufficiently high to prevent complications from strain‐induced crystallization), and in swelling equilibrium in benzene at room temperature. Small to moderately large proportions of dangling chains were found to have less of an effect on the elongation modulus than might be expected, and similarly a relatively small effect on the degree of equilibrium swelling. Most importantly, comparisons of constant values of the high deformation modulus show that dangling‐chain irregularities decrease both the maximum extensibility of a network and its ultimate strength.
Dicyandiamide analysis and solubility in epoxy resins
Authors: Hagnauer Gary L. , Dunn David A. 
Published: April 2003

AbstractA simple procedure is described for the rapid, quantitative analysis of dicyandiamide in epoxy resins and epoxy resin prepregs. High performance liquid chromatography is used to analyze for dicyandiamide and to investigate the solubility behavior of dicyandiamide and 3‐(p‐chlorophenyl)‐1,1‐dimethylurea (Monuron) in liquid epoxy resins. Solubility expressions and differential heats of solution are determined. The formation of soluble amine‐epoxy reaction products and epoxy resin additives such as Monuron are found to enhance the solubility of dicyandiamide.
Wettability of glow discharge polymers
Authors: Sharma Ashok K. , Millich Frank , Hellmuth Eckhard W. 
Published: April 2003

AbstractTreatment of good adhering glow discharge polymerized propylene (GDPP) coatings with reactive gas plasma from oxygen, nitrogen, or water (produced in a tubular reactor operation at 27.1 MHz) results in surfaces characterized by more hydrophilic interactions. Zisman's plots indicate a change in surface energy after such treatment. Transmission electron microscopy depicts that the pronounced improvement in wettability of GDPP polymer after oxygen plasma treatment in part results from the high surface development in the polymer. However, the effect is not permanent. The wettability of plasma‐treated polymer diminishes with time and reaches a limiting value in 2–3 months indicating structural rearrangements at the polymer surface. Argon, carbon monoxide, or bromotrichloromethane plasma does not change the polymer surface wettability significantly. In contrast to the O2 plasma‐treated GDPP polymer, a glow discharged polymer synthesized from ϵ‐caprolactam maintains its inherent hydrophilicily over an extended period of time.
Shrinkage and internal stress during curing of epoxide resins
Authors: Shimbo M. , Ochi M. , Shigeta Y. 
Published: April 2003

AbstractThe shrinkage and internal stress of bisphenol‐type epoxide resins cured with aliphatic α,ω‐diamines, H2N(CH2)m′NH2(m′ = 2, 4, 6, and 12), were investigated by measuring the change of density and the strain of the steel ring embedded in the cured resins. Internal stress was found to be induced by the shrinkage occurring in the cooling process from the glass transition temperature (Tg) to room temperature. Shrinkage and internal stress increased with increase in the concentration of network chains and Tg of the cured systems, and then with a decrease in m′ of the curing agents. It appears that the reductions in the concentration of network chains and Tg were necessary to reduce the shrinkage and internal stress caused by the curing.
Thermal diffusivity and conductivity of crystalline polymers
Authors: Choy C. L. , Ong E. L. , Chen F. C. 
Published: April 2003

AbstractThe thermal diffusivity and conductivity of the isotropic and drawn samples of five semicrystalline polymers—nylon 6, poly(ethylene terephthalate), poly(butylene terephthalate), polybutene‐1, and poly(4‐methylpentene‐1)—were measured by the flash method over the temperature range 100–350 K. The temperature dependence of the thermal diffusivity was found to follow a simple phenomenological pattern, while a more detailed understanding of the temperature dependence and the effect of orientation on thermal conductivity was obtained by using the modified Maxwell model.
Studies on the light‐focusing plastic rod. IX. Chemical composition of the copolymer rod‐diethylene glycol bis(allyl carbonate) with 2,2,3,3‐tetrafluoropropyl methacrylate
Authors: Ohtsuka Yasuji , Terao Yukiko 
Published: April 2003

AbstractFor the preparation of the light‐focusing plastic rod (LFR) a gel rod of partially polymerized diethylene glycol bis(allyl carbonate) (CR‐39) was immersed in 2,2,3,3‐tetrafluoropropyl methacrylate (4FMA) followed by heat treatment under nitrogen. Variations in the chemical composition in this process indicated the following mode of copolymerization: copolymerization of 4FMA with the allylic group in the gel rod occurs to some extent in the immersion process, but a significant amount of either 4FMA or CR‐39 remains in the rod. Under heat treatment, these monomers copolymerize to a CR‐39–4FMA network copolymer, the preferential component of the LFR. Excellent imaging of the representative LFR is also demonstrated.