bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion of low molecular weight substances into a fiber with skin‐core structure—rigorous solution of the diffusion in a coaxial cylinder of multiple components
Authors: Fukuda Mitsuhiro , Kawai Hiromichi 
Published: May 2005

AbstractThe diffusion equation of low molecular weight substances (penetrant) into a coaxial cylinder of multiple components (m) was formulated in general and solved rigorously. As the simplest but a practical case of m = 2, which corresponds to the diffusion of penetrant into fibrous material with skin and core structure, the diffusion of penetrant was analyzed in detail. That is, changes in the penetrant concentration distribution within the coaxial dual cylinder of skin and core components and the total amount of penetrant sorbed within the cylinder both with time after exposing the cylinder to atmosphere of fixed penetrant concentration of Cout were calculated with variation of the diffusion coefficient ratio (D1/D2) and the radius ratio (R2/R1), where D1 and D2 are the diffusion coefficients of penetrant in the core and the skin, and R2 and R1 are the radii of the fibrous material and the core, respectively. Keeping (R2/R1) at a constant value of 1.2 but varying (D1/D2) from 104 to 10−2, the penetrant concentration distribution was calculated and found to be much different particularly within the core between (D1/D2) > 1 and (D1/D2) < 1. The sorption curves were also found to deviate in their respective ways from that of Fickian curve of a homogeneous cylinder with (D1/D2) = 1 except at initial stage of sorption. Further, by keeping (D1/D2) constant but varying (R2/R1) from 1.1 to 1.5, the effects of relative skin thickness upon the sorption curve were studied.
Principal features of structural relaxation in glassy polymers. A Review
Authors: Mijović Jovan , Nicolais Luigi , D'amore Alberto , Kenny Jose M. 
Published: May 2005

AbstractThe principal features of models of structural relaxation in the glassy state were reviewed. The concepts of fictive temperature as the structural parameter and nonexponentiality and nonlinearity of structural relaxations were described. Various expressions for the structural relaxation time were presented and compared. One particular model was selected and utilized in a parametric optimization study of structural relaxation. Model predictions were checked against experimental results obtained by volumetric and calorimetric measurements.
Mechanism of shear modification of low density polyethylene
Authors: Van Prooyen M. , Bremner T. , Rudin A. 
Published: May 2005

AbstractIn this paper we address the aspects associated with shear modification of low density polyethylene by extrusion. By successive passes of the polymer through an extruder it can be shown that both the melt viscosity and melt elasticity are reduced by shear modification. These reversible variations are not accompanied by significant changes in molecular weight distribution. The major effects of extrusion are to decrease the amount of elastically effecitve material. Study of proton relaxation times at 150°C shows that the melt comprises regions of relatively ordered, entangled, and unentangled polymer. Shearing reduces the proportion of more ordered material. The elastically effective anchors that are reduced by shearing are regions with restricted segmental mobility rather than conventional entanglements or intermolecular knots. Successive extrusions produce a relatively small decrease in the number of such constraints to molecular motion. Repeated shearing has a diminishing effect on the proportion of more ordered material in the polyethlene melt. This parallels observations of the effects of repeated shear modification on the properties of polyethylene films and other extrudates.
Modeling of polypropylene degradation during reactive extrusion with implications for process control
Authors: Pabedinskas A. , Cluett W. R. , Balke S. T. 
Published: May 2005

AbstractThis paper presents the development of a model for free radical initiated polypropylene degradation during reactive extrusion that combines a kinetic model of the polypropylene degradation reaction with a simplified model of the melting mechanism in the extruder. The free radical initiated degradation of polypropylene is characterized by a narrowing of the molecular weight distribution (MWD) and a decrease in the molecular weight averages. A high temperature SEC is used to determine MWD's for three different commercially available polypropylenes degraded at various initiator concentrations in a 1.5 inch single screw extruder (L/D = 24:1). The predictions of the kinetic model alone and the combined kinetic‐melting model are compared with the experimentally determined MWD's and molecular weight averages for the degraded polypropylenes. The predictions of a modified kinetic model that includes the possibility of termination by combination are also examined. The kinetic‐melting model is found to provide significantly improved predictions of the experimentally determined MWD's and molecular weight averages in comparison to the original kinetic model. A viscosity‐molecular weight relationship is also developed, which is then used to determine the gain of the degradation process as a function of the initiator concentration from the molecular weight averages predicted by the kinetic‐melting model. Earlier work has shown such prior knowledge of the process gain can be used to significantly improve the performance of process control schemes for the degradation process.
Nonisothermal elongational behavior of blends with liquid crystalline polymers
Authors: La Mantia F. P. , Valenza A. , Scargiali F. 
Published: May 2005

AbstractMeasurements of melt strength and breaking stretching ratio of several blends of thermoplastic polymers with liquid crystalline polymers are presented. The melt strength behavior depends not only on the viscosity of the blends but also on the temperature dependence of the viscosity. In particular, even if the viscosities of the blends are, at the extrusion temperature, lower than that of the thermoplastic matrices, the melt strength can be larger than that of the pure thermoplastics if its viscosity‐temperature curve exceeds that of the matrices far from the solidification temperature. This behavior allows one to spin or film blow these blends despite the low viscosity.
Isocyanate trimerization kinetics and heat transfer in structural reaction injection molding
Authors: Viola G. G. , Schmeal W. R. 
Published: May 2005

AbstractGuidelines are developed for molding large composite parts via structural reaction injection molding using glass preforms and polyisocyanurate resins. These are based on numerical simulations of the simultaneous heat transfer and reaction kinetics of a commercial system during and after mold filling. Premised requirements are that resin does not gel before the mold is filled, yet, reactions are sufficiently vigorous to approach completion. An existing mechanistic kinetic model is used and material parameters found from a chemical kinetics study employing an insulated cup. It is found desirable to use a high mold temperature and a low preform temperature in molding. Nondimensionalization of the governing equations reveals the existence of a Nusselt number (Nu), which describes the relative importance of heat transfer between resin and glass relative to thermal diffusion to the mold wall. With a Nusselt number of about 50 or higher it is possible to use the cooling capacity of the preform to extend gel time. The magnitude of Nu is influenced by part thickness, glass fraction, strand diameter, and flow velocity. Thus, the effect of the preform on extending resin gel time is within control of the molder.
Annealing effects in poly(phenylene sulfide) as observed by dynamic mechanical analysis
Authors: Scobbo J. J. , Hwang C. R. 
Published: May 2005

AbstractPoly(phenylene sulfide) (PPS) is a semicrystalline engineering resin with exceptional solvent resistance and thermal performance. Properties such as these are directly related to the high crystallinity of PPS. In order to exploit its crystalline nature, PPS should be molded at a high tool temperature (hot oil tool) to allow for the highest crystallization rate, and therefore the highest percent crystallinity. Alternately, if a low mold temperature is used, the molded parts should be annealed. This latter process has been studied for injection molded neat PPS resin for various annealing temperatures. Two different grades of PPS were studied that represent cured and linear types. Samples were studied as‐molded, and annealed at 160, 180, 200 and 220°C. Increases in glass transition temperature were noted upon annealing. An increase in storage modulus was also noted for annealed samples. This increase persisted up to approximately the annealing temperature. Differential scanning calorimetry has been used to show that annealing PPS allows for a secondary crystallization to occur whereby an endotherm appears that corresponds to the secondary crystalline phase melting near the annealing temperature. As the annealing temperature is increased, the area of the endotherm increases. The secondary crystallization explains the higher storage modulus that persists up to the annealing temperature. These results are discussed in terms of crystallinity and overall effect on heat distortion temperature.
In‐line monitoring of molten polymers: Near infrared spectroscopy, robust probes, and rapid data analysis
Authors: Hansen Marion G. , Khettry Atul 
Published: May 2005

AbstractThe concept of improved product quality and reduced costs has revolutionized analytical techniques in the polymer industry. It has brought in‐line analysis to the forefront, with near infrared (NIR) spectroscopy proving to be a very viable technique for such operations. A system for continuous in‐line near infrared monitoring of molten polymer blends, copolymers, and polymer reactions is being developed. The ultimate objective is to use this monitoring system to develop feedback control for polymeric processes. Experiments on blends of polystyrene and poly(phenylene oxide) have been performed by using a flow cell, located at the exit port of a single‐screw extruder. Qualitative analysis of spectral data has been substantiated by a variety of quantitative (multivariate) techniques. Robust calibration models, suitable for on‐line predictions, have been developed. The success of in‐line process analysis depends on the performance of fiber‐optic probes that are inserted into the process stream. These probes normally succumb to the demands of the rigorous process environment, typical of polymeric processes, i.e., high temperatures, high pressures, and adverse chemical conditions. Design and development of fiber‐optic probes that are capable of withstanding such harsh conditions have also been undertaken. Results will be reported on the polymeric systems and optical probes.
Ballistic performance of polycarbonate/polyester and polycarbonate/styrene‐acrylonitrile microlayer sheets
Authors: Kohlman William G. 
Published: May 2005

AbstractExtruded microlayer sheets of Polycarbonate/Polyester (PC/PCTG) and Polycarbonate/Styrene‐acrylonitrile (PC/SAN) were tested for ballistic performance. Composition of the microlayer sheets ranged from 60 to 100 percent polycarbonate. The number of layers in the approximately 3 mm thick sheets ranged from on for the blend control samples to 3713 layers in the PC/PCTG sheets. The normalized ballistic test results showed that some samples performed as well as as and slightly better than injection molded polycarbonate samples. The failure mechanism was affected by the composition and the number of layers. Increasing composition of polycarbonate and number of layers decreased the percent of brittle failures.
A comparative study on the electrochemical properties of ring‐substituted polyanilines
Authors: Dai Lizong , Xu Yiting , He Yunyou , Gal Jean‐Yves , Wu Huihuang 
Published: May 2005

AbstractThe redox behavior of polyanilines with ring‐substituted groups synthesized by chemical polymerization, poly‐2,5‐dimethoxyaniline (PDMAn), poly‐m‐chloroaniline (PmClAn) and poly‐o‐toluidine (POT), was studied and the morphology and crystal orientation of platinum particles deposited on these polymer membranes was compared. The oxidation of isopropanol on platinized polyaniline‐modified electrodes as a model reaction was also investigated to examine the electrocatalytic properties of the polymers. The results show that the first oxidation potential of the polymers increases in the following sequence: PDMAn, POT and then PmClAn, which can be explained in terms of the electronic and steric effects of ring‐substituted groups. The growth of Pt particles electrodeposited on doping‐state POT and PDMAn polymer membranes takes place by a ‘progressive nucleation mechanism’, but by an ‘instantaneous nucleation mechanism’ on PmClAn. Platinum crystallites trend towards preferred‐orientation and Pt (200) is the preferred face, but the degree of preferred orientation depends on the polymer. The oxidation potentials of isopropanol are located near 0.3 V, and the oxidation currents increase on platinized polymer‐modified electrodes, indicating that the interaction of polymer with Pt particles might improve the catalytic activity of Pt. Polyanilines act not only as dispersion media but also change the electronic properties of Pt crystalline grains. Copyright © 2005 Society of Chemical Industry
Synthesis of polyurethane cationomers with anil groups: intramolecular proton transfer in salicylideneanil structures
Authors: Buruiana Emil C , Olaru Mihaela , Strat Mitache , Strat Geta , Simionescu Bogdan C 
Published: May 2005

AbstractThree new o‐hydroxy Schiff bases, 2‐chloromethyl‐N‐(2‐hydroxybenzilidene)aniline, 3‐(11‐bromoundecanoyloxymethyl)‐N‐(2‐hydroxybenzilidene)aniline and 4‐chloromethylphenyl (carbamoyloxymethyl‐2‐hydroxybenzylidene)aniline, used as quaternization agents for a polyetherurethane precursor based on poly(tetramethylene oxide) diol of 2000 g mol−1 average molar mass (PTMO), 2,4‐toluene diisocyanate and N‐methyldiethanolamine (1:3:2 molar ratio), have been synthesized in order to obtain polymeric films with fluorescent properties. The structure and the photochromic mechanism of the salicylideneanil units were investigated. The excited state intramolecular proton‐transfer process (ESIPT) with the cis‐ and trans‐keto isomers formation as intermediate compounds and the formation of a keto tautomer were evidenced by a large Stokes shifted emission (100 nm). Copyright © 2005 Society of Chemical Industry
Synthesis of a novel luminescent copolymer based on bisphenol A
Authors: Trad Hager , Jaballah Najmeddine , Majdoub Mustapha , Roudesli Sadok , Roussel Joseph , Fave Jean Louis 
Published: May 2005

AbstractA new luminescent copolymer (BPAEt2‐BP; Scheme 1), with short alternating divinylbiphenyl units and O‐diethylated bisphenol A (BPAEt2), was synthesized via the Wittig reaction. The polymer is fully soluble in common organic solvents and has a number‐average molecular weight of 4600 g mol−1 with a polydispersity index of 1.79. The structure of the polymer was confirmed by 1H NMR, 13C NMR, FTIR and Raman analysis. Thermal analysis of the polymer showed good stability up to 280 °C. Furthermore, polymer film absorbs at 360 nm and emits in the blue at 426 and 451 nm. The band‐gap calculated from the UV‐vis spectrum was about 2.80 eV. A single‐layer device of the configuration indium tin oxide (ITO)/BPAEt2‐BP/Al has a relatively low turn‐on voltage of 3 V. Copyright © 2005 Society of Chemical Industry
An activated neodymium‐based catalyst for styrene polymerization
Authors: Wang Jing , Wu Yi‐Xian , Xu Xu , Zhu Han , Wu Guan‐Ying 
Published: May 2005

AbstractCoordination polymerization of styrene with a ternary catalyst system composed of catalyst neodymium tricarboxylate (Nd), co‐catalyst Al(i‐Bu)3 (Al) and chlorinating agent trichloroethane (Cl) was carried out in cyclohexane. The effects of the catalyst system preparation procedure and of the reaction conditions on catalytic activity, molecular weight and molecular weight distribution of the resultant polymers were investigated. The catalytic activity depended mainly on the molar ratios of Al/Nd and of Cl/Nd and on the ageing temperature and polymerization temperature. High polymerization conversion and high catalytic activity could be obtained at high Al/Nd ratios and/or at high ageing temperature. The catalyst system exhibited high activity of 8.32 × 104 g polystyrene (mol Nd h)−1 at 50 °C. The molecular weight of the polymers obtained reached high weight‐average (Mw) values (Mw = 4.35 × 105 g mol−1) when Al/Nd = 8, but relatively low values (6000–11 000 g mol−1) at high Al/Nd ratios. Copyright © 2005 Society of Chemical Industry
Supported zirconocene catalyst for preventing reactor fouling in ethylene polymerization
Authors: Entezami Ali , Najafi Moghadam Peyman 
Published: May 2005

AbstractThe commercial interest of metallocene complexes for olefin polymerization has led to additional efforts to prepare suitable metallocene complexes efficiently and economically. Ethylene polymerization was carried out with a series of heterogeneous catalysts which were prepared in various Zr/silica ratios by immobilization of Ind2ZrCl2 preactivated with methylaluminoxane (MAO) on silica. This method to form the catalyst system resulted in a polymerization catalyst with reduced fouling tendencies and improved reactor operability. Polymerization of ethylene was conducted in Buchi reactors in a slurry phase under mild pressure. Some of the physical properties of the obtained polymers were also determined. Copyright © 2005 Society of Chemical Industry
Intramolecular hydrogen bonding in o‐hydroxyaryl Schiff bases
Authors: Filarowski Aleksander 
Published: May 2005

AbstractThis review deals with selected aspects of research on o‐hydroxyaryl Schiff bases. Special attention is given to results obtained by x‐ray, IR, UV and NMR spectroscopic methods and quantum‐mechanical calculations that allow a better understanding of the nature of o‐hydroxyaryl Schiff bases. The paper reports on studies of sterically modified o‐hydroxyaryl Schiff bases with an intramolecular hydrogen bond made short owing to steric repulsion. The following points are focused upon: structural and energetic analysis of the steric effect and its influence on the hydrogen bond length; proton localization and the proton transfer process; the impact of proton transfer on the chelate and phenol rings in the intramolecular hydrogen bond; a generalized scheme of tautomer equilibrium and its study with the use of experimental and theoretical methods; some discrepancies found in standard parameters for a particular tautomeric form; calculations of the potential energy curve for basic tautomer forms; influence of the steric effect on the potential curve shape; and a review of semi‐empirical and quantum‐mechanical calculations of molecular structures in the ground state. Copyright © 2005 John Wiley & Sons, Ltd.
Steric and aromatic impact on intramolecular hydrogen bonds in o‐hydroxyaryl ketones and ketimines
Authors: Filarowski Aleksander , Kochel Andrzej , Cieslik Katarzyna , Koll Aleksander 
Published: May 2005

AbstractX‐ray measurements at 100 K and quantum‐mechanical calculations showed a domination of the enol (OH) form in o‐hydroxyaryl ketones [6‐methoxy‐2‐hydroxyacetophenone (6OMeK), 4‐methoxy‐2‐hydroxyacetophenone (4OMeK), 5‐chloro‐4‐methyl‐2‐hydroxybenzophenone (5Cl4MeK) and 2‐hydroxyacetonaphthone (o‐HAN)], whereas a prevailing proton‐transfer (NH) form was found in o‐hydroxyacetonaphthylimine [2‐(N‐methyl‐α‐iminoethyl)naphthol (o‐HIN)]. The effective mechanism of the reduction in hydrogen bridge length due to steric repulsion in the o‐hydroxyaryl ketones is presented. The following phenomena were found: a decrease in phenol ring aromaticity caused by the proton‐transfer process, dependence of the HOMA index of aromaticity on the HOSE index defining the destabilization of the chelate ring and a dependence of the HOMA index on the lengths of the carbonyl bonds. Moreover, a correlation between phenol ring aromaticity [HOMA(phenol)] and the pseudo‐aromatic ring [HOSE(chelate)] is shown. Correlations between structural parameters of the chelate ring [d(C—O), d(Caryl—Calkyl)] and aromatic rings [HOMA(phenol)] of the o‐hydroxyaryl ketimines and ketones are presented. Copyright © 2005 John Wiley & Sons, Ltd.
Structural modifications resulting from proton transfer in complexes of phenols with pyridine
Authors: Majerz Irena , Kwiatkowska Emilia , Koll Aleksander 
Published: May 2005

AbstractThe structural consequences of proton transfer in complexes of phenol (1), 2,6‐dichlorophenol (2), 4‐nitrophenol (3) and 2,6‐dichloro‐4‐nitrophenol (4) with pyridine were analyzed on the basis of results of B3LYP/6–31G** calculations. Three methods of describing the progress of proton transfer are proposed: the O—H [d(OH)] and C—O [d(CO)] bond lengths and the fraction XPT of the proton transfer form, calculated from the values of the dipole moments. The d(OH) parameter reveals behaviour near to XPT and can be used as a universal measure of the degree of proton transfer. The d(CO) parameter gives nearly linear dependences for various structural parameters, but independent estimation of the specific effects of the substituents is necessary, as separate correlations for each complex are found. A role of resonance interaction in systems containing a p‐NO2 substituent is demonstrated. Copyright © 2005 John Wiley & Sons, Ltd.
Kinetics of base‐catalysed ring closure of methyl 2,6‐dinitrophenylsulfanylethanoate
Authors: Janík Marek , Štěrba Vojeslav , Černý Jiří , Macháček Vladimír , Jansa Petr 
Published: May 2005

AbstractThe base‐catalysed ring closure of methyl 2,6‐dinitrophenylsulfanylethanoate gives 2‐methoxycarbonyl‐7‐nitrobenzo[d]thiazole‐3‐oxide. The kinetics of this ring closure were studied by means of UV–visible spectrophotometry in methanolic buffers of N‐methylmorpholine–N‐methylmorpholinium chloride and N‐methylpiperidine–N‐methylpiperidinium chloride at 25°C at ionic strength I = 0.1 mol l−1. The dependences of kobs on the base concentration are not linear, their slopes decreasing with increasing base concentration at constant ratio of the buffer components. The reaction mechanism was suggested on the basis of comparison with the ring closure kinetics of methyl 2,4,6‐trinitrophenylsulfanylethanoate. The rate‐limiting step of the reaction sequence consists in formation of the conjugated base of substrate 1. Copyright © 2005 John Wiley & Sons, Ltd.
Estimation of reactivity ratios of acrylate copolymers by 1H‐NMR
Authors: Nithianandam V. S. , Kaleem K. , Srinivasan K. S. V. , Joseph K. T. 
Published: May 2005

AbstractCopolymers of methyl methacrylate (MMA) and dimethylaminomethacrylate (DMAEM) are useful for binding of enzymes. Copolymerization of MMA and DMAEM was carried out in dioxane using benzoyl peroxide as an initiator at 70°C. The estimation of the composition of MMA and DMAEM in copolymer was carried by 1H‐NMR. The reactivity ratio was found to be r1 = 1.20 and r2 = 0.19 by Kelen‐Tüdös method and r1 = 1.24 and r2 = 0.21 by Finemann‐Ross method.
Network formation during vinyl polymerization via inorganic particles
Authors: Nagata K. , Turner D. T. 
Published: May 2005

AbstractMethyl methacrylate containing a small amount of 4‐methacryloxyethyl trimellitate anhydride (1.0–1.5 wt %) yielded an insoluble network when polymerized in the presence of various inorganic powders, such as lithium aluminum silicate. This unexpected result was obtained for polymerization initiated either by exposure to γ‐rays or by heating with azobisisobutyronitrile. In contrast, polymerization in the absence of inorganic powder gave the expected soluble products. Therefore, it is concluded that the inorganic particles play a role in network formation. In order to account for network formation even in a supernatant layer of clear monomer, i.e., above the centrifuged sedimentation volume of the powder, it is suggested that the monomer reacts on the surface of particles to form a diffusive crosslinking agent.