bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular dynamics of polybenzimidazole and contributions from chaos
Authors: Iwamoto N. 
Published: May 2005

AbstractMolecular dynamics has been used to study possible dynamic mechanisms that may contribute to the property degradation known to exist for polybenzimidazole (PBI) upon hydration. During this study, chaotic movements of a chain pair were observed. Changes in onset and duration of this movement were also observed, which depended upon both hydration state and stress direction involved. Such trends suggested that specific mechanistic pathways may exist that could directly lead to property (such as modulus) loss.
Multiobjective dynamic optimization of a nonvaporizing nylon 6 batch reactor
Authors: Wajge Rajesh M. , Gupta Santosh K. 
Published: May 2005

AbstractMultiobjective dynamic optimization has been carried out on a nonvaporizing nylon 6 batch reactor. Three objective functions have been identified, viz., minimization of the concentration of unreacted monomer in the product, minimization of the dimer concentration, and minimization of the reaction time, for producing polymer having a specified value, μn, d, of the number average chain length. Two problems have been studied in this paper, each consisting of two objective functions taken from the above set. Pareto solutions have been generated using an algorithm based on Pontryagin's minimum principle and the method of Lagrangian multipliers. The effects of various physical and computational parameters have been studied, and methods have been developed to overcome the numerical difficulties that arise during the solution. The Pareto sets so generated can be coupled with the surrogate worth trade‐off (SWT) method, which facilitates interaction with a decision maker (DM). The optimal temperature histories obtained for the two problems studied are quite different and suggest that one must solve the three‐dimensional problem in which the vector objective function incorporates all three objective functions. Results from the present study could be used as starting guesses to converge rapidly on the solution of the three‐dimensional problem.
Thermal behavior of hydrostatically extruded polycarbonate and high‐impact polystyrene
Authors: Ariyama Takashi , Nakayama Toshio 
Published: May 2005

AbstractEffects of hydrostatic extrusion on the thermal properties of polycarbonate (PC) and of high‐impact polystyrene (HIPS) were studied using differential scanning calorimeter (DSC) measurements. A glass transition temperature (Tg) and a peak temperature were determined from the DSC curves for both PC and HIPS extrudates. The Tg values of the PC extrudates, with a percentage reduction in area, R, from 40 to 50%, change appreciably from the value for the as–received PC. The results of the hydrostatic extrusion of the PC billets suggest that a two stage deformation process of molecular chains may be involved. Shear‐banding is observed for HIPS extrudates with R = 30 to 60%; this fact indicates that a sub‐glass transition (β‐transition) occurs at temperatures below Tg. It is suggested that the molecular chains of the HIPS extrudate with R = 70% are oriented in the direction of hydrostatic extrusion. The deformation mechanism of molecular chains caused by the hydrostatic extrusion is discussed.
Effect of grafting degree and side PEO chain length on the ionic conductivities of NBR‐g‐PEO based polymer electrolytes
Authors: Kim Dong‐Won , Park Jung‐Ki , Gong Myoung‐Seon , Song Hae‐Young 
Published: May 2005

AbstractComb‐shaped graft polymers were synthesized and complexed with a LiCF3SO3 salt to form a new class of polymer electrolytes. The polymers based on an acrylonitrile‐butadiene copolymer (NBR) have pendant, short‐chain poly(ethylene oxide) (PEO) grafted onto a butadiene unit. The characteristics of these polymer electrolytes were investigated in terms of number of pendant EO groups and grafting degree in the graft copolymer. The maximum conductivity was observed at the optimum side PEO chain length, and the PEO chain length for the maximum conductivity decreased with an increase in the grafting degree. And a solid 7Li NMR relaxation technique was used to study the local environments and dynamics of the ions in the polymer electrolytes. The maximum conductivity value obtained from our study was three orders of magnitude higher than that of classical PEO‐based electrolytes at ambient temperature. These improved low temperature conducting polymers with higher relative mechanical strength are expected to be suitable for practical applications, such as in rechargeable lithium batteries or electrochromic devices.
Viscoelastic‐plastic deformation behavior of polypropylene after cyclic preloadings
Authors: Ariyama Takashi 
Published: May 2005

AbstractStress‐relaxation behavior is studied in polypropylene samples subjected to different cyclic preloadings and to simple tension. The relaxation tests are performed under different sets of strain amplitude, number of cycles, and strain rate, using a closed‐loop, electrohydraulic, servocontrolled testing machine. The calculated stress‐strain curves are determined from a constitutive equation based on an overstress theory in which an equilibrium stress and a viscosity function are treated. The calculated results agree well with the experimental ones. It is concluded that the overstress theory explains the nonlinear viscoelastic‐plastic behavior of polypropylene.
Thermal and mechanical properties of injection molded liquid crystalline polymer/amorphous polymer blends
Authors: Engberg K. , Strömberg O. , Martinsson J. , Gedde U. W. 
Published: May 2005

AbstractInjection molded samples of binary blends of Vectra (LCP) and the three amorphous polymers polyethersulfone (PES), polycarbonate (PC), and aromatic poly(ester carbonate) (APEC) have been subjected to morphological and rheological characterization, and coefficients of linear thermal expansion and Young's moduli have been determined. The Young's modulus of the PES/LCP blends exhibited a near lower‐bound behavior that could be predicted by the one‐adjustable‐parameter equations of Halpin‐Tsai (ζ = 0.18) and Takayanaga (b = 0.23), whereas the coefficients of linear thermal expansion followed the Takayanaga equation with a value of b = 0.50. The chain orientation of the LCP component was essentially constant in all PES/LCP blends with a Herman's orientation parameter of 0.39 ± 0.03. Transesterification reactions led to randomization of the constituents of the PC/LCP and APEC/LCP blends. The effect was more pronounced in the PC/LCP blends. The introduction of the LCP into the PC/LCP blends led to no reduction in melt viscosity and no self‐reinforcement. APEC/LCP exhibited self‐reinforcement in blends with a content greater than 27 vol% LCP, and especially the blend with 67 vol% LCP. The self‐reinforcement was caused by the presence of an oriented LCP phase, confirmed by X‐ray diffraction, and by improved interfacial bonding, presumably resulting from the transesterification reactions occurring at the phase boundaries.
Fatigue crack propagation behavior of cellulose esters
Authors: Moskala Eric J. , Pecorini Thomas J. 
Published: May 2005

AbstractThe effect of plasticizer concentration on fatigue crack propagation (FCP) rate in cellulose acetate‐propionate (CAP) was determined. Compact tension specimens were machined from 6.2 mm‐thick injection molded plaques and tested on an MTS servohydraulic testing machine using a sinusoidal waveform with a frequency of 1 Hz. Two FCP mechanisms were identified: a crazing mechanism, which dominated at low values of stress intensity factor range, ΔK, and a shear yielding mechanism, which dominated at high values of ΔK. The value of ΔK at the onset of the transition from the crazing mechanism to the shear yielding mechanism was a function of plasticizer concentration, and therefore yield strength of the CAP. The transition in crack propagation mechanism created a V‐shaped feature on the fracture surface, which could be used to weight the contributions from the two crack propagation mechanisms to the overall FCP rate.
The behavior of bubbles in Bueche model fluids
Authors: Brujan Emil‐Alexandru 
Published: May 2005

AbstractThe nonlinear oscillation of a spherical gas bubble in polymer solutions was theoretically analyzed. Using the rheological equation of Bueche model fluid, the equation of motion and the pressure equation for a bubble are derived. According to the numerical calculations, the effects of rheological properties and initial radius of the bubble on the bubble radius‐time history, pressure at the bubble wall, critical and equilibrium radii of the bubble, as well as pressure distribution in liquid are discussed.
About the existence of a percolation threshold in solid solution of N‐isopropylcarbazole/polycarbonate mixtures
Authors: Santos‐Lémus Simón J. 
Published: May 2005

AbstractDirect current (DC) dark conductivity, (σ) measurements have been carried out in thin films of N‐isopropylcarbazole/polycarbonate mixtures (NIPC/PC) for relative weight ratio (x) in the range 2 to 80% by weight of NIPC in PC at room temperature. The experimental results suggest a non‐percolative transport in the concentration range explored. In the range 20 to 80%, a hopping character and power law dependence σ ∼ (x − xc)3 is found with xc = 0.16. In the range 2 to 20% these relations are masked by the influence of hops involving polymer matrix which makes such a system not a suitable model for testing percolation ideas.
Characterization of poly(3‐octylthiophene). II: Melt rheological characterization
Authors: Heffner Glenn W. , Rochefort Wille E. , Pearson Dale S. 
Published: May 2005

AbstractThe poly(3‐alkythiophenes) are electrically conducting polymers which are of particular interest due to their melt‐processibility. We have studied the melt properties of poly(3‐octylthiophene) (P3OT) by dynamic rheological measurements at temperatures between 180 and 250°C. The samples investigated have molecular weights in the range Mw = 30,000 to 400,000 and have been carefully characterized by dilute solution techniques, Residual iron chloride, a reagent used in the polymerization of these materials, was found to cause a high degree of crosslinking in the polymer melt. By contrast, samples which had been carefully purified demonstrated a negligible rate of crosslinking in a nitrogen atmosphere; however, the presence of air and higher temperatures were found to increase the rate of crosslinking substantially. The temperature dependence of the viscoelastic properties was characterized according to the principles of time‐temperature superposition, and the influence of molecular weight was also evaluated. Overall, the rheological behavior was determined to be similar to that commonly observed for linear flexible polymers, which is in agreement with the results of our solution characterization of these materials.
Structure and mechanical anisotropy of cold‐rolled ultrahigh molecular weight polypropylene
Authors: Hibi Sadao , Niwa Takahiro , Wang Chi , Kyu Thein , Lin Jar‐Shyong 
Published: May 2005

AbstractWide angle X‐ray diffraction pole figure, small angle X‐ray scattering (SAXS), and refractive index techniques have been employed to investigate structure and deformation mechanisms in unidirectionally cold‐rolled ultrahigh molecular weight polypropylene (UHMWPP) films. All reciprocal lattice vectors (plane normals) of (110), (040), and (130) were found to populate in the film normal (thickness) direction, suggesting that more than one orientation process must be involved in the deformation. SAXS studies on the cold‐rolled UHMWPP reveal an oriented lamellar structure with its long axis perpendicular to the rolled direction, however, the lamellae are somewhat tilted. Refractive index and tensile measurements were undertaken to determine the optical and mechanical anisotropy of the cold‐rolled UHMWPP films. A similar study was undertaken of unidirectionally rolled conventional polypropylene (PP) for comparison.
The leveling of thermosetting waterborne coatings. Part II: Drying of coated wet films
Authors: Kojima Shunji , Moriga Toshinori 
Published: May 2005

AbstractEvaporation behavior of water/solvent blends was estimated using the universal functional activity coefficient, UNIFAC, method. The evaporation rate from a free surface of a waterborne coating, WBC, containing a co‐solvent was experimentally determined. These results were used to estimate the evaporation rate from wet films of a WBC containing a variety of co‐solvents with a range of initial thickness. Knowing the composition of the WBC during the drying process, the change in the viscosity and the surface tension was determined. The results strongly support the development of a surface tension gradient in the film. It is also suggested that a surface tension gradient would accelerate the leveling of the ribs if a proper co‐solvent were employed.
Effect of casting solvent on the heterogeneity of films of polymer blends
Authors: Lu Shaoxiang , Pearce Eli M. , Kwei T. K. 
Published: May 2005

AbstractThe miscibility window of the 50/50 w/w poly(styrene‐co‐4‐vinylphenyl)‐dimethylsilanol/poly(n‐butyl methacrylate) (ST‐VPDMS/PBMA) blends prepared from toluene was studied and determined to be in the VPDMS composition range of 4 to 18 mole% in the copolymers. The observed miscibility window was to be compared to the range of 9 to 34 mole% found for the blends prepared from methyl ethyl ketone which was capable of competing for hydrogen bonding. The fact that the observed miscibility windows are influenced by the choice of solvents illustrates that an equilibrium state of polymer mixing is not always attained in solvent casting films and that caution needs to be exercised in studying polymer miscibility when solvent cast films are used.
The effect of crystallinity on the light scattering of regenerated cellulose tubular films
Authors: Larena Alcia , Pinot Gabriel 
Published: May 2005

AbstractAn experimental study of the effect of crystallinity on the light scattering of regenerated cellulose tubular films is reported. Several films were prepared by varying manufacturing conditions, so that thickness and surface roughness were maintained approximately constant and the degrees of crystallinity varied between 38 and 66%. The scattered radiation intensity, measured between 220 and 550 nm decreases with the increasing wavelength. It was demonstrated that for the polymeric films studied, there was excellent agreement between crystallinity and scattering radiation intensity for a given wavelength. It was found that for crystallinity values less than around 57%, scattered radiation intensity decreases with increasing crystallinity, the reverse of that for crystallinity values greater than that percentage.
Impact behavior of microcellular foams of polystyrene and styrene‐acrylonitrile copolymer, and single‐edge‐notched tensile toughness of microcellular foams of polystyrene, styrene‐acrylonitrile copolymer, and palycarbonate
Authors: Collias Dimitris I. , Baird Donald G. 
Published: May 2005

AbstractIn the first part of this series of papers, the tensile properties of microcellular foams of polystyrene (PS), styrene‐acrylonitrile copolymer (SAN), and polycarbonate (PC) were reported. In this part, the impact properties of unnotched, sharply and bluntly notched samples of microcellularly foamed PS and SAN samples were studied. Furthermore, the effects of the sharpness of the notch as well as of the speed of the test were studied by comparing the impact tests with the single‐edge‐notched (SEN) tensile tests, which were carried out for the PS, SAN, and PC sample. Some limited improvement in impact and SEN tensile properties was exhibited in some experimental conditions. The impact properties of microcellularly foamed PC samples are reported elsewhere.
Compatibility and tensile behavior of polypropylene/ethylene‐propylene rubber blends
Authors: Nomura T. , Nishio T. , Fujii T. , Sakai J. , Yamamoto M. , Uemura A. , Kakugo M. 
Published: May 2005

AbstractThis study clarifies and quantifies factors which increase the ductility of a low‐molecular‐weight propylene homopolymer having an intrinsic viscosity of 0.89 dl/g. The tensile behavior of homopolymer/ethylene‐propylene rubber (EPR) blends was studied from the viewpoint of the associated molecular structure of EPR and its compatibility with the homopolymer. When EPR is “dissolved” in a homopolymer, the glass transition temperature (Tg) of the amorphous phase of a homopolymer was found to shift to a lower temperature, with homopolymer/EPR compatibility being subsequently evaluated using this shift, i.e., Δtg. Results show two conditions are required to improve the ductility of the low‐molecular weight propylene homopolymer: ΔTg must be ≥ 3°C and ≥ 30 wt% EPR must be blended with the homopolymer.
Tension effects on the properties of oxidized polyacrylonitrile and carbon fibers during continuous oxidation
Authors: Tsai Jin‐Shy 
Published: May 2005

AbstractIn this study we used continuous oxidizing equipment to produce carbon fiber. The results show when the stretch of the fiber during continuous oxidation is increased, the orientation and modulus of resultant carbon fiber is unexpectedly decreased. This effect is much different from other published results. In this case, the stretching occurs after the cyclization of the molecular chains in the amorphous region. The stretching leads to the scission of some cyclized molecular chains in the amorphous region and the shrinkage of the crystalline region.
Change of molecular weight distribution of statistical poly(styrene‐co‐acrylonitriles) with compositio of copolymer
Authors: Mencer H. J. , Gomzi Z. , Rogošić M. 
Published: May 2005

AbstractStatistical poly(styrene‐co‐acrylonitrile) (SAN) copolymes with varying mole fractions of comonomer units have been synthesized in a batch reactor. The intrinsic viscosity and gel permeation chromatography (GPC) patterns of model copolymer samples were the basic experimental results. Chromatographic patterns of SAN copolymer samples were converted into molecular weight distributions and afterwards fitted to the theoretical distribution functions. The correlation between the composition of copolymers and the best fitted model distribution (Schulz's two parameters distribution in this case) was established. The treatment of data shows that parameter α is inversely proportional to the content of acrylonitrile units in the sample and indicates the molecular weight interval. Parameter b shows the invariability of the molecular weight distribution shape.
Magnesium chloride‐supported, high‐mileage catalysts for olefin polymerization. V. BET, porosimetry, and x‐ray diffraction studies
Authors: Chien James C. W. , Wu Jiun‐Chen , Kuo Chi‐I 
Published: May 2005

AbstractThe physical state of the material obtained during the various stages of preparation of a typical MgCl2‐supported, high‐mileage propylene polymerization catalyst was studied by BET, mercury porosimetry, and x‐ray diffraction techniques. The starting MgCl2 and the substance after HCl treatment have negligible BET surface areas. Mercury porosimetry showed that they have large pores with radii > 200 nm which are probably crevices between MgCl2 crystallites. The most pronounced physical changes occur during dry porcelain ball milling in the presence of ethyl benzoate. After 60 h or more of ball milling the material had a 5.1–7.3 m2 g−1 BET surface area, twice the pore surface area, and a smaller pore radius than before ball milling and a large reduction in crystallite sizes to almost ultimate dimensions. The crystallites were probably held together by complexation with ethyl benzoate in the form of large agglomerates. Subsequent reactions with p‐cresol and triethyl aluminum had minor effects in further reduction of the MgCl2 crystallite size but efficiently brokeup the agglomerates. The final refluxing with TiCl4 increased the BET surface area to 110–150 m2 g−1 but may have increased the crystallite size somewhat due to cocrystallization of TiCl3 and AlCl3 with MgCl2. There may have been only 8–10 crystallites in each catalyst particle. The surface structure of the catalyst resembled those of the classical Ziegler‐Natta γ‐TiCl3·0.33 AlCl3 catalyst.
Metal chelates in vinyl polymerization: Kinetics and mechanism of acrylonitrile polymerization initiated by Cu(II) imine complexes
Authors: Marjit D. N. , Kalpagam V. , Nandi U. S. 
Published: May 2005

AbstractThe free radical polymerization of acrylonitrile (AN) initiated by Cu(II) 4‐anilino 2‐one [Cu(II) ANIPO] Cu(II), 4‐p‐toluedeno 3‐pentene 2‐one [Cu(II) TPO], and Cu(II) 4‐p‐nitroanilino 3‐pentene 2‐one [Cu(II) NAPO] was studied in benzene at 50 and 60°C and in carbon tetrachloride (CCl4), dimethyl sulfoxide (DMSO), and methanol (MeOH) at 60°C. Although the polymerization proceeded in a heterogeneous phase, it followed the kinetics of a homogeneous process. The monomer exponents were ≥2 at two different temperatures and in different solvents. The square‐root dependence of Rp on initiator concentration and higher monomer exponents accounted for a 1:2 complex formation between the chelate and monomer. The complex formation was shown by ultraviolet (UV) study. The activation energies, kinetics, and chain transfer constants were also evaluated.
Electrolytically initiated polymerization of N‐vinylcarbazole
Authors: Mano Eloisa B. , Calafate Bettina A. L. 
Published: May 2005

AbstractPolymerization of N‐vinylcarbazole was studied systematically using electroinitiation with several quaternary ammonium salts as electrolytes in methylene chloride solution. Polymer was obtained only when the following electrolytes were used: tetraethylammonium perchlorate, tetrabutylammonium perchlorate, and tetrabutylammonium fluoroborate. Polymeric products of molecular weight 104–105 were formed in the anodic compartment of a divided cell. IR and 13C‐NMR spectra showed that the structures of the polymers were similar to those produced by conventional cationic polymerization, which suggests a similar mechanism for the resulting anodic product.
Selective surface modification of polymers by means of hydrogen and oxygen plasmas
Authors: Clark D. T. , Wilson R. 
Published: May 2005

AbstractAn ESCA investigation has been made of the changes in surface functionalization for a series of polymers effected by means of low‐powered inductively coupled rf plasmas excited in hydrogen and oxygen. Reactions in each case are confined to the outermost surfaces of the polymer films and the use of oxygen plasmas leads to extensive oxidative functionalization. Bisphenol‐A polycarbonate and polyethylene terephthalate exhibit similar overall reactivities to both oxygen and hydrogen plasmas, while polystyrene is shown to be substantially more reactive than high‐density polyethylene to the plasma treatments of interest in this work. Comparison has been made of the effects of straight hydrogen and oxygen plasmas and of sequential hydrogen/oxygen and oxygen/hydrogen plasma treatments.