bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of metal cation type on the structure and properties of ethylene ionomers
Authors: Hirasawa Eisaku , Yamamoto Yoshimasa , Tadano Kenji , Yano Shinichi 
Published: April 2003

AbstractThermal properties by DSC, stiffness, melt viscosity, tensile properties, and dynamic mechanical properties were measured for the Na+, K+, Mg2+, Zn2+, Cu2+, Mn2+, and Co2+ salts of poly(ethylene‐co‐methacrylic acid) (EMAA). The changes in the structure and properties with increasing neutralization are larger in the alkaline and alkaline earth metal salts than in the transition metal salts. The stiffness shows a maximum at 33% neutralization in both the alkaline and alkaline earth metal salts, while no maxima are found up to 60% neutralization in the transition metal salts. The microphase separation of salt group aggregates is observed in both the alkaline and alkaline earth metal salts, but is not seen in the transition metal salts. These differences were attributed to both the stronger ionic interactions and the larger number of carboxyl groups associated with the alkaline and alkaline earth metal salts in the ordered structure of ionic salt groups (ionic crystallites). The mechanical properties measured at low strain, such as stiffness and yield stress, strongly depend on the degree of the crystalline order of the ionic crystallites. The high‐strain properties, such as tensile strength and elongation at break, depend on the strength of the ionic interactions and the valence of the cation.
The heterogeneous character of the dilute acid hydrolysis of crystalline cellulose. II. Hydrolysis in sulfuric acid
Authors: Lin Chyong‐Huey , Conner Anthony H. , Hill Charles G. 
Published: April 2003

AbstractNine prehydrolyzed cellulose samples, including native, mercerized, and regenerated celluloses were hydrolyzed in 2% sulfuric acid at 150, 160, and 170°C. The first‐order rate constants and the weight average degrees of polymerization (by size exclusion chromatography) were determined for each sample. The results indicate that Sharples' end‐attack model [Trans. Faraday Soc., 53, 1003 (1957)] is consistent with kinetic data for cellulose II samples, but is not appropriate for characterizing the reactions of cellulose I samples.
Acid–Base interactions in filler characterization by inverse gas chromatography
Authors: Tiburcio Astrophel C. , Manson John A. 
Published: April 2003

AbstractGlass beads as model fillers were characterized by inverse gas chromatography (IGC) according to the Lewis acid–Lewis base (donor–acceptor) concepts as adapted by Fowkes. A range of organic probes (acidic chloromethanes, neutral n‐alkanes, and basic acetone and diethylether) was used to elucidate the acid–base nature of the glass bead surface. The untreated glass bead surface was found to contain predominantly acidic sites while the treated glass bead (treated with an aminopropyltriethoxysilane coupling agent) was more basic than its unmodified counterpart. Calculation of the enthalpies of acid–base interactions (ΔHab) form the retention behavior of the basic probes with the two glass beads produced at least an 8‐kJ/mol difference between the two glass types, the ΔHab of the untreated glass being greater than the treated glass. A difference of this magnitude is sufficient to produce a corresponding difference in the interfacial behavior of the two glass types. Therefore, IGC can be used as a quantitative technique for characterizing filler surfaces.
Studies on the preparation and properties of conductive polymers. Part II. Novel method to prepare metallized plastics from metal chelates of polyamides
Authors: Yen Chih‐Chao , Huang Chueh‐Jung , Chang Teh‐Chou 
Published: April 2003

AbstractNew metallized films were obtained by the reduction of polyamide metal chelate films with reducing agents. Polyamide metal chelates films exhibited excellent surface resistivity around 10°–101 Ω/cm2 when treated with sodium borohydride aqueous solutions. Aqueous solutions of polyamide–formic acid with metal salts, and films prepared from those solutions, were analyzed by UV‐visible and IR spectroscopy, respectively, in order to investigate and identify the structure of the polyamide metal chelates. Factors that include kinds and concentrations of metal salts, kinds and concentrations of reducing agents, and reduction time, which may affect the conductivity of metallized films, were investigated. The surfaces of these films were treated with sodium borohydride aqueous solution to form a definite metallic luster appearance. The surfaces of these conductive films were proved to be metallized, by means of ESCA analysis. The strongly adhered metal on the films was believed to be responsible for the improvement in electrical conductivity. The mechanical properties and scanning electron microscope (SEM) observations were also studied.
Rheological properties of polypropylene/high‐density polyethylene blend melts. II. Dynamic viscoelastic properties
Authors: Fujiyama Mitsuyoshi , Kawasaki Youtoku 
Published: April 2003

AbstractThree kinds of isotactic polypropylenes with different MFI were melt‐blended with three kinds of high‐density polyethylenes with different MFI using a screw extruder and the dynamic viscoelastic properties were studied. The storage moduli G′(ω) of the blends showed second plateaus and the dynamic viscosities η′(ω) of the blends showed two‐step drops with increasing angular frequency ω. Such phenomenon was particularly notable for blend systems in which particles of lower viscosity were suspended in the disperse medium of higher viscosity and is considered to be the cause of abnormally large die swell.
Permeability properties of glycol chitosan membrane modified with thiol groups
Authors: Kubota Naoji , Ohga Kazuya , Moriguchi Mitsuaki 
Published: April 2003

AbstractWater‐soluble glycol chitosan (GC), having the ability to form a membrane, was modified with 3,3′‐dithiodipropionic acid (DTPA), a functional group that causes the thiol ⟷ disulfide transition through redox reaction. The membrane derived from this modified GC was water‐insoluble. The permeabilities of KCI and socrose through the GC membrane modified with DTPA (MDTPA), the reduced membrane (MSH), and the oxidized membrane (MSS) were investigated. The permeability through the MSH membrane increased twofold relative to that through the MDTPA membrane, and the MSS membrane showed a 60% decrease in the permeability, which had increased in the case of the MSH membrane. The permeability of sucrose was lower and more changeable than that of KCl. These permeation phenomena were discussed from the viewpoint that the thiol ⟷ disulfide transition is responsible for the water content of each membrane.
Determination of molecular weight for poly(vinyl butyral) using size exclusion chromatography/low‐angle laser light scattering (SEC/LALLS) in hexafluoroisopropanol
Authors: Remsen Edward E. 
Published: April 2003

AbstractSize exclusion chromatography/low‐angle laser light‐scattering (SEC/LALLS) determinations of molecular weight for poly(vinyl butyral) (PVB) using hexafluoroisopropanol (HFIP) as the polymer solvent and chromatographic mobile phase are described. The use of HFIP provided aggregate‐free SEC/LALLS chromatograms from which molecular weight distribution averages were calculated. Comparison of SEC/LALLS molecular weights determined in HFIP with similar data obtained using tetrahydrofuran as the polymer solvent and chromatographic mobile phase indicated that the former is more generally applicable for PVB of different vinyl alcohol content.
Prediction of cure time for a rubber cement used for conveyer belt splicing
Authors: Focke W. W. , Van Eeden G. S. 
Published: April 2003

AbstractThe evolution of bonding strength for a commercial cold vulcanizing rubber cement was determined using small–mscale simulated conveyer belt splicing. Peel and shear data obtained under isothermal conditions fit a modified Avrami model X = 1 − exp(−kt1/2), where X is the degree of ultimate shear or peel bond strength obtained and the rate constant k shows a typical Arrhenius type temperature dependence k = 42 exp(1670/T) min1/2 for peel strength, and k = 57 exp(−2000/T) min1/2 for shear strength. (T is the absolute temperature in K.) Bonding strength evolution under nonisothermal cure conditions can be estimated by integrating the general rate expression dX/dt = 0.5k2(1 − X)/(−ln[1 − X]).
Particle size control in emulsions of hydrocarbon soluble polymers
Authors: Falk John C. , Benedetto M. A. 
Published: April 2003

AbstractHydrocarbon solutions of polybutadiene, polyisoprene, and polystyrene may be converted into emulsions. The hydrocarbon solvent may then be removed by distillation. The molecular weight of the polymer controls the particle size of its emulsion. An increase in polymer molecular weight causes an increase in the particle size of its emulsion.
Epoxy resins based on aromatic glycidylamines. IV. Preparation of N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane from aniline and analysis of the product by GPC and HPLC
Authors: Podzimek Š. , Dobáš I. , Švestka Š. , Tkaczyk M. , Kubín M. , Štěrba V. 
Published: April 2003

AbstractEpoxy resins containing N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) were prepared from aniline and epichlorohydrin and analyzed by GPC and HPLC. The product composition was compared with that of resins prepared from 4,4′‐diaminodiphenylmethane (DDM) and epichlorohydrin, which had been analyzed in our previous work. A new byproduct designated Y4 was isolated by semipreparative HPLC and identified by NMR and mass spectroscopy. The course of formaldehyde condensation with N,N‐dichlorohydrin of aniline (DCHA) was followed by GPC and HPLC and the mechanism of formation of Y4 was proposed on the basis of obtained results. Attention was also paid to the differences in reactivity of DCHA diastereoisomers.
Effects of fibers on the glass transition temperature of polyphenylene sulfide composites
Authors: Rebenfeld Ludwig , Desio Glenn P. , Wu James C. 
Published: April 2003

AbstractThe glass transition temperature (Tg) of polyphenylene sulfide (PPS), and of several commercial and model PPS prepregs with aramid, carbon, and glass fibers was studied by means of differential scanning calorimetry. The Tg of unreinforced PPS was found to range between 83–90°C, depending on source and molecular weight. The Tg of the commercial prepregs was depressed by about 3–5°C from that of the corresponding unfilled PPS, an effect that was ascribed to the plasticization of the PPS by one or more components of the fiber finish (size) that was assumed to have diffused into the PPS polymer. In the case of model prepregs prepared with finish‐free reinforcing fibers, an expected increase in Tg was observed. In model prepregs prepared with finished (sized) aramid fibers, the Tg was depressed as in the case of the commercial prepregs. With sized AS‐4 carbon fibers, the Tg was increased, but significantly less so than with unsized AS‐4 fibers. With sized glass fibers, the same slight increase in Tg was observed as with unsized glass fibers. The increase or decrease of Tg in all cases was a function of the fiber content in the model PPS prepregs.
Preceramic organoboron–silicon polymers
Authors: Hsu Ming‐Ta S. , Chen Timothy S. , Riccitiello Salvatore R. 
Published: April 2003

AbstractSeveral boron‐containing organosilicon polymers were synthesized from a sodium‐coupling reaction of silicon and boron halides with and without alkyl halide in hydrocarbon solvents. The B–Si preceramic polymers were characterized using techniques such as IR, UV, and NMR spectrometry, gel permeation chromatography, elemental analysis, molecular weight measurement, and thermal analyses (TGA, DSC, DTA, and TMA). The chemical structures of the preceramic polymers were postulated based on the analytical results. Black ceramic materials were obtained from the precursor polymers upon thermal degradation at temperatures above 1000°C in an inert atmosphere. The precursor polymers had a ceramic yield of up to 70%. Thermogravimetric analysis of the ceramic material in air at a flow rate of 100 mL/min showed it was stable up to 1000°C with little weight gain or loss. Several methods were used to characterize the ceramic materials: XRD, solid NMR, high‐temperature DTA, elemental analysis, and acid digestion. The analyses indicated that the ceramic materials comprised a mixture of silicon carbide (SiC), silicon borides (SiB4, SiB6), and amorphous Si–B–C ceramics, with small amounts of silica and free silicon.
Liquid crystalline polymer laminates
Authors: Avramova N. , Fakirov S. 
Published: April 2003

AbstractOn the basis of a poly(ethylene terephthalate) copolyester containing 60 mol %p‐hydroxybenzoic acid, thin liquid crystalline films (160 μm thick) are obtained by melting the polymer at 300°C and chilling at 0°C. The undrawn films obtained have a high degree of orientation as evidenced by X‐ray measurements. Due to molecular orientation, these films are characterized by their excellent mechanical properties. In order to avoid losses in the mechanical strength due to increase in their thickness, laminates are prepared using thin liquid crystalline films. Lamination is carried out by annealing under pressure at 170°C for 6 h, resulting in samples with excellent mechanical properties regardless of their thickness. A method is proposed that makes it possible to combine the unique mechanical properties of thin films of liquid crystalline polymers with a lamination process in order to obtain thick and very strong materials.
Chemical modification of jute fibers. II: A study on the Fe2+/H2O2‐initiated graft copolymerization of methyl methacrylate, acrylonitrile, and acrylamide onto jute fibers
Authors: Moharana Sibendu , Tripathy S. S. 
Published: April 2003

AbstractThe study of graft copolymerization of methyl methacrylate, acrylonitrile, and acrylamide onto both defatted and bleached jute fibers using the ferrous ammonium sulfate / H2O2 redox initiator system has been made. To determine the optimum conditions of grafting, the effects of concentrations of ferrous ammonium sulfate, monomer, H2O2; time and temperature on percentage of graft yield have been studied. Acrylamide was found to graft onto the fiber only at a fixed ferrous ammonium ion concentration (5 × 10−4M). Kinetic studies showed that the rates of grafting follow the second‐order mechanism. The activation energies of the reactions were found to be 3.351 and 2.53 kcal/mol in the methyl methacrylate and acrylonitrile systems, respectively. The grafted fibers have been characterized by thermogravimetric analysis, IR spectroscopy, and XRD studies.
Thermal behavior and curing kinetics of poly(carbosilane)
Authors: Suwardie Herman , Kalyon Dilhan M. , Kovenklioglu Suphan 
Published: April 2003

AbstractThis study focuses on the thermal behavior and curing kinetics of a commercially available poly(carbosilane). Poly(carbosilane) is used for the production of silicon carbide (SiC) fibers by high‐temperature pyrolysis. Thermal characterization studies were carried out by employing a differential scanning calorimeter and thermogravimetric analyzer. The change in the chemical structure during curing with oxygen was studied with an infrared spectrometer. It was found that the uncured poly(carbosilane) would froth under a nitrogen environment around 450°C. Curing with oxygen, which results in crosslinking at the surface, enables the sample to retain its shape during high‐temperature pyrolysis. Curing was carried out at various temperatures, and the kinetics of the curing reactions were characterized.
Thermal conductivity of glass fiber reinforced polypropylene under high pressure
Authors: Yen C. L. , Tseng H. C. , Wang Y. Z. , Hsieh K. H. 
Published: April 2003

AbstractThe thermal conductivities of molten polypropylene and its glass fiber composites were measured by the compensating hot wire method. The testing apparatus empolyed was designed and tested in our laboratory. The measurements were carried out with temperatures ranging from 170 to 230°C and pressures from 1 to 2000 kg/cm2. The results show that the thermal conductivity increases with increasing pressure and glass fiber content, but is almost independent of temperature. The thermal conductivity data were fitted satisfactorily with a proposed empirical equation for polypropylene and Lewies‐Nielsen equation for the composites, respectively.
Translucent blends of chlorinated polyethylene with poly(vinyl chloride)
Authors: Tse A. , Laakso R. , Baer E. , Hiltner A. 
Published: April 2003

AbstractSome experimental chlorinated polyethylene (CPE) resins that produced translucent blends with PVC were used to study the effects of CPE chlorine content and chlorine distribution on the morphology, optical clarity, and toughness of blends with PVC. The CPE resins were characterized in terms of the glass transition temperature, residual crystallinity, density, and refractive index. Increasing residual crystallinity and increasing chlorine content both increased the refractive index closer to that of PVC. A linear relationship was observed between the fourth power of the refractive index and the CPE glass transition temperature. With a phase‐separated blend morphology in all cases, improved transparency was achieved in this system by reducing the refractive index difference between CPE and PVC. Both haze and transparency showed the predicted linear dependence on the square of the refractive index difference. To a first approximation, modifications of the experimental CPE resins that improved optical transparency of the blends also tended to reduce the toughness enhancement.
Unified theory and guidelines on adhesion
Authors: Chung Frank H. 
Published: April 2003

AbstractA new approach was proposed to consolidate the many adhesion theories into one coherent concept. The maximum attractive force between two sets of molecules (adhesion strength) is derived from the Lennard–Jones potential function and calculated with measured bond length and bond energy. It leads to two criteria for strong adhesion: intimate molecular contact of closer than 9 Å (necessary condition), and maximum attractive force with minimum potential energy (sufficient condition). The criteria conform to the key elements of most prior adhesion theories. Seven prior adhesion theories and their relevance to these two criteria were briefly reviewed/discussed. In order to draw up a set of guidelines on adhesion and supplement the missing pieces of information, 21 model polymers of varied functionality were synthesized to study (1) the effect of polar groups on adhesion and (2) the effect of polymer conformations on adhesion. The results indicate that polar groups are more effective in polymer backbone than in side chains for promoting adhesion. The presence of both hydrogen donors and acceptors in the same backbone maximizes adhesion. True (active) solvents enhance adhesion, cosolvents (latent solvents) boost adhesion by inducing favorable conformation of polymers in solution, but thinners (diluents) reduce adhesion. The set of guidelines covered the effects of functional groups, solvent blends, pigment loadings, adhesion promotion, and adhesion loss.
Dielectric properties above the glass transition for a series of epoxide prepolymers
Authors: Koike Tsuneo , Tanaka Ryohei 
Published: April 2003

AbstractDielectric properties above the glass transition have been investigated for a series of bisphenol‐A type epoxide prepolymers (388 ≤ M̄w ≤ 2640). Dielectric measurements were performed over a frequency range of 50 Hz–1 MHz using a vertical parallel plate cell which was constructed in the laboratory. The dielectric α‐relaxation for each prepolymer fits the empirical model of the Havriliak–Negami equation. The temperature dependence of the dielectric relaxation time τ is described by the Williams–Landel–Ferry (WLF) equation as well as that of the direct current conductivity σ, which can be measured using the same cell. The relationship between τ and σ, σ· τm = const, is derived from experimental results. The exponent m, which depends on the molecular weight of the prepolymer, is considered to correspond to the ratio of the segmental mobility to ionic mobility. The dielectric loss ε″ can be used as an indicator of the direct current conduction in the temperatures where the ionic component in ε″ becomes much larger than the dipole one.
The analysis of the surface chemical structure of biomedical aliphatic polyanhydrides using XPS and ToF‐SIMS
Authors: Davies M. C. , Khan M. A. , Domb A. , Langer R. , Watts J. F. , Paul A. J. 
Published: April 2003

AbstractThe surface chemical structure of a range of aliphatic polyanhydride films has been examined using XPS and ToF‐SIMS. The XPS data confirms the purity of the surface, and the experimental surface elemental ratios are in good general agreement with the known stoichiometry of the polyanhydrides. The ToF‐SIMS spectra of the polyanhydrides are shown to be significantly different. The SIMS data conforms to a systematic fragmentation, in both negative‐ and positive‐ion SSIMS spectra, occurring throughout the entire series of polyanhydrides examined. Radical cations are observed in the positive‐ion spectra. These results are discussed in terms of the general fragmentation patterns observed in the SIMS analysis of polymers. The combined use of ToF‐SIMS and XPS is shown, to provide a detailed insight into the interfacial chemical structure of these polyanhydrides.
On the dynamic mechanical behavior of poly(ethyl methacrylate) reinforced with kevlar fibers
Authors: Ribelles J. L. Gómez , Sebastià J. Mañó , Soler R. Martí , Pradas M. Monleón , Greus A. Ribes , Antón J. J. Suay 
Published: April 2003

AbstractThe dynamic mechanical relaxation spectra of a series of composites with a matrix of poly(ethyl methacrylate) reinforced with continuous Kevlar fibers present several characteristics that have been proposed in the literature regarding polymer composites as a proof of the existence of an interphase between the polymeric matrix and the filler with mechanical properties different from both: The α‐relaxation, associated with the glass transition of the matrix, is shifted in the temperature axis, and a peak appears in the tan δ vs. temperature plot, which was not present either in the matrix or in the fiber relaxation spectra. Nevertheless, a simple block model which does not include the existence of such an interphase is able to reproduce not only the dependence of the loss tangent and storage modulus with the fiber content, but also the shift of the α‐relaxation and the presence of the new α′ peak in the composites.
Studies on polyurea‐amide membranes
Authors: Joshi S. V. , Rao A. V. 
Published: April 2003

AbstractDifferent polyurea‐amides were synthesized by interfacial polymerization of acid chloride, diamine, and diisocyanate. The polymers and the membranes were characterized for their RO/UF applications. Highly porous membranes could be prepared from the sulfuric acid‐based casting formulation and the membrane casting conditions were established. The resulting membranes are not asymmetric as they give high permeability to water and salt solutions. They are found to be resistant to many organic solvents, thus making them useful in concentration/separation applications. Whole milk, egg albumin and Na‐alginate were found to be rejected 100% by these membranes, while solutes of about 20,000 Mw are found to be rejected to the extent of 70‐80%.