bluuebunny/crossref_metadata_2025_split huggingface dataset:
Semianalytical solution for epoxy‐amine curing in the presence of nonisothermal effects
Authors: Gupta Sanjay , Agarwal B. D. , Kumar Anil 
Published: May 2005

AbstractThe curing of epoxy‐amine polymer has been modeled by the reaction of functional groups, and the mole balance of these is governed by a set of six nonlinear differential equations. In this work, we have first developed a complete analytical solution for isothermal curing. For nonisothermal curing, we have divided the domain of hydroxyl group concentration β into small increments Δβ and adopted our analytical results for this domain. In addition, we solved the energy balance equation analytically and obtained the temperature rise for Δβ. We have compared our results with those obtained from the Runge Kutta numerical solutions. We have shown that our semianalytical technique is about a thousand times more efficient and faster.
A property trend study of polybenzimidazole using molecular modeling
Authors: Iwamoto N. 
Published: May 2005

AbstractMolecular mechanics and dynamics have become a standard analysis tool used in drug design and synthesis, but it has not generally been used as part of structural and mechanical analysis. The need for such tools is an obvious extension of structure‐property correlations known in polymer formulation, engineering, and manufacture. This study probes the use of mechanics and dynamics techniques to help explain property trends found in hydrated polybenzimidazole (PBI).
Rheological properties of structured fluids
Authors: De Kee D. , Chan Man Fong C. F. 
Published: May 2005

AbstractThe kinetic theory proposed by Soong and Liu for describing the rheological properties of structured fluids has been extended to predict shear‐thinning, shear‐thickening, thixotropy, and antithixotropy in different ranges of shear rates. Viscoelastic properties, as given by the Gordon‐Schowalter Maxwell model, with a non‐constant modulus, have also been considered. The theoretical predictions are compared with the predictions of a model used by Ait‐Kadi, et al. (1988), for a hydrolyzed polyacrylamide solution containing 20 g/1 of NaCl. the predictions and experimental data for the viscosity and primary normal stress coefficient are in reasonably good agreement. The stress growth functions have also been calculated and have been found to be consistent with experimental observations.
Processability and thermal properties of blends of high density polyethylene, poly (ethylene terephthalate), and ethyl vinyl acetate compatibilizer
Authors: Chen C. , Lai F. S. 
Published: May 2005

AbstractBecause of differences in chemical structure and rheological characteristics, high density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) are incompatible when blended during recycling of PET soft drink bottles. To improve the properties of the blends, ethylene vinyl acetate copolymer (EVA) was used as a compatibilizer. Based on torque rheometer tests, the higher the concentration of PET in the blends, the higher the initial loading torque. Blends of 50% HDPE and 50% PET had the lowest equilibrium torque. Equilibrium torque was highest at 5% EVA. The presence of EVA made only a slight difference in the glass transition temperatures of HDPE/PET blends. Higher EVA content in the blend resulted in a lower melting endotherm. Thermogravimetric analysis showed that thermal stability was independent of EVA content; but the more PET in the blend, the lower the final weight loss.
Correlation for volume phase transition of polymeric gel (vinyl alcohol‐sodium acrylate copolymer) in alcohol‐water solutions
Authors: Ishidao Toru , Iwai Yoshio , Hashimoto Yasuhiko , Arai Yasuhiko 
Published: May 2005

AbstractA thermodynamic model was proposed to correlate the phase behavior of a swelling polymeric gel (vinyl alcohol‐sodium acrylate copolymer) and the volume phase transition in alcohol (methanol, ethanol or propanol)‐water solutions. The model is based on the Flory‐Huggins formula for polymer solution coupled with the osmotic pressure by rubber elasticity proposed by Flory. The volume change behavior and the equilibrium concentrations inside and outside the gel were successfully correlated using the present model.
Heterogeneous suspension polymerization of vinyl chloride: Phase distribution and evolution
Authors: Schmidt M. J. , Farber J. N. , Vallés E. M. 
Published: May 2005

AbstractA model for the phase distribution and evolution of the heterogeneous (suspension) polymerization of vinyl chloride is presented. Experimental information on pressure, temperature, and conversion has been obtained from a 34 liter bench reactor reproducing reaction conditions and product properties typical of industrial operation. A calculation procedure based on simple plant data is proposed for the description of the phase compositions and their evolution over the entire process. Results based on classical Flory‐Huggins theory of solutions are presented and compared with existing data.
Dielectric properties of blends of polycarbonate and acrylonitrile‐butadiene‐styrene copolymer
Authors: Steeman P. A. M. , Maurer F. H. J. , Van Turnhout J. 
Published: May 2005

AbstractThe low frequency dielectric properties of polymeric blends of polycarbonate (PC) and acrylonitrile‐butadiene‐styrene (ABS) were studied in the temperature interval of 100 to 170°C. Attention was focused on a 60/40 (m/m) PC/ABS blend. The results were compared with dynamic mechanical measurements in torsion and with the results of a morphological investigation using scanning electron microscopy (SEM). Besides the relaxations at the glass transition temperatures of the components an additional strong low frequency dielectric dispersion was observed, which was not found in mechanical measurements. This low frequency polarization process is due to interfacial polarization at the boundaries between conductive ABS and non‐conductive or slightly‐conductive PC. It is shown how this process can be described by the dielectric models for two‐phase heterogeneous materials. The Looyenga model offers the best description of the detected effects, while the Hanai model is less suitable. The shape factor of the ABS phase as used for modeling the dielectric properties agrees well with the observed morphology using SEM. It is shown for the dielectric measurements on the 75/25, 60/40, and 45/55 (m/m) PC/ABS blends how the connectivity of the ABS phase can be sensitively derived from the eletrical conductivity of the blend, whereas mechanical measurements are highly senstive to the connectivity of the PC phase.
In‐situ cure monitoring of diamine cured epoxy by fiberoptic fluorimetry using extrinsic reactive fluorophore
Authors: Dang Wenbin , Sung Nak‐Ho 
Published: May 2005

AbstractThis paper describes the application of a molecular sensor for in‐situ monitoring of epoxy‐diamine cure via remote sensing fiberoptic probes. A custom‐built, fiberoptic fluorimeter allows on‐line recording of fluorescence spectra directly from the cure environment. Cure reactions in epoxy‐diamine network, such as diglycidyl ether of bisphenol A‐diaminodiphenyl sulfone (DGEBA‐DDS) or diglycidyl ether of butanediol‐diaminodiphenyl sulfone (DGEB‐DDS), have been monitored by a reactive molecular sensor, diamino azobenzene (DAA). DAA exhibits sensitive changes in UV‐visible and fluorescence spectra due to the conversion of its primary amine groups to secondary and tertiary amine groups. Fluorescence intensities are correlated with extent of reaction in epoxy network and processing parameters, such as cure temperatures and time. The use of an internal reference dye for normalization of fluorescence intensities is necessary for the quantitative correlation of spectral signals with the network structure. Variables affecting the fluorescence intensity such as excitation volume, probe location, excitation intensity fluctuation, temperature, and background intensities from optical fiber can be calibrated by normalizing the signal intensities against the internal reference. Sulforhodamine 101 was found to be a satisfactory reference dye which provides stable, readable signals over temperatures up to 200°C.
Kinetic parameters estimation for cure reaction of epoxy based vinyl ester resin
Authors: Lee Jhong Ho , Lee Jae Wook 
Published: May 2005

AbstractA new graphical estimation technique is proposed for the determination of the kinetic parameters describing an autocatalytic reaction. A differential scanning calorimeter was used to monitor the reaction kinetics of an epoxy‐based vinyl ester resin. The method utilizes information from a zero initial reaction rate, conversation at vitrification, the ratio of reaction rate constants under different isothermal conditions, and characteristics of the phenomenological kinetic model with assumptions being made about the overall reaction order. By fitting data to the integrated reaction rate equation with adjustments for the isothermal conditions, the kinetic parameters are estimated without using a linear or nonlinear regression method. Different kinetic parameters can be estimated from data before and after the gel point which was obtained from the relationship between the glass transition temperature and the degree of cure.
Mechanical properties and morphology of liquid crystalline copolyester‐amide and amorphous polyamide blends
Authors: Jang Sang Hee , Kim Bong Shik 
Published: May 2005

AbstractBlends of an amorphous polyamide (PA) and a liquid crystalline copolyesteramide (LCP), poly(naphthoate‐aminophenoterephthalate) were prepared in a twin‐screw extruder. Specimens for mechanical testing were prepared by injection molding. Morphological, thermal, mechanical, and rheological properties were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X‐ray diffractometry, capillary rheometry, and a tensile tester, respectively. The tensile mechanical behavior of the LCP/PA blends was found to be affected by their compositions and specimen thickness. Tensile testing revealed that the tensile mechanical behavior of the LCP/PA blends was very similar to that of polymeric composite and the tensile strength of the LCP/PA (50/50) blend was approximately two times of the value of PA homopolymer and exceeded that of pure LCP. The morphology of the LCP/PA blends was also found to be affected by their compositions. SEM studies revealed that the liquid crystalline polymer (LCP) formed finely dispersed spherical domains in the PA matrix and the inclusions were deformed into fibrils from the spherical droplets with increasing LCP content. It has been found that droplet and fiber formations lead to low and high strength material, respectively. In particular, at specific LCP content (50 wt%), the tensile strength of the LCP/PA blend exceeded that of pure LCP. The improvement in tensile properties is likely due to the reinforcement of the PA matrix by the fibrous LCP phase as observed by SEM. A distinct shell‐core morphology was found to develop in the injection molded samples of these blends. This is believed to have a synergistic effect on the tensile properties of the LCP/PA blends. The rheological behavior of the LCP/PA blends was found to be very different from that of the parent polymers and significant viscosity reductions were observed for the LCP/PA (50/50) blend. Based upon DSC, these blends have shown to be incompatible in the entire range of concentrations.
Air drag on fine filaments at oblique and normal angles to the air stream
Authors: Ju Y. D. , Shambaugh Robert L. 
Published: May 2005

AbstractMeasurements are reported for air drag on fine filaments whose axes are oriented at oblique and normal angles to the air velocity. In terms of the drag coefficient CDN the data are fit well by the following relation: CDN = 6.96(ReDN)−0.440(d/d0)0.404, where ReDN is the Reynolds number based on flow normal to the fiber axis, and d/d0 is a dimensionless fiber diameter. A wide range of conditions were tested: filament diameters ranged from 13 to 390 microns, gas velocities ranged from 22 to 83 m/s, and fiber Reynolds numbers ranged from 29 to 2120.
Numerical nonisothermal flow analysis of non‐Newtonian fluid in a nonintermeshing counter‐rotating twin screw extruder
Authors: Fukuoka Takamasa , Min Kyonsuku 
Published: May 2005

AbstractA simulation technique for nonisothermal flow analysis of non‐Newtonian fluid in a nonintermeshing counter‐rotating twin screw extruder was developed by modifying the flow analysis network (FAN) method. The local shear viscosity in the flow field was calculated by an iteration method combing the three types of mean shear rate functions. The modified Cross model and an Arrhenius‐type function for temperature dependence were also introduced. Streamlines in the flow field are represented by computing the movements of fluid particles based on the flux fields. The computed residence time from the streamlines led us to solve the energy equation by replacing the coordinate system. The profiles of pressure, shear rate, shear viscosity, temperature, and residence time were simulated. The influence of operating and geometrical parameters on the screw characteristics are discussed. Further, residence time distribution (RTD), strain distribution function (SDF), and interfacial area growth are predicted from the computation of streamlines to analyze the mixing capabilities of the extruder.
Extrudate roughness of high‐density polyethylene and linear low‐density polyethylene: Determination of key parameters using screening design
Authors: Wang X. , Clément B. , Carreau P. J. , Lafleur P. G. 
Published: May 2005

AbstractA screening design is used to establish the contribution of various parameters to the roughness of cylindrical extrudates. A dimensionless response variable is proposed to characterize the extrudate roughness, and the effects of ten parameters on this roughness response were examined. Two polyethylenes (one high density and one linear low density) were investigated using a 45 mm single screw extruder. The results show that the main parameters affecting the extrudate roughness are, in order of importance, apparent shear stress at the die wall, die diameter, ratio of die length to diameter, and type of polymer. The other six parameters (the use of an additive, recycling, type of entrance adapter, die material, die temperature, melt temperature) were found to have a non‐significant contribution to roughness.
Rheological properties of blends of lithium‐ or sodium‐sulfonated polystyrene ionomers with polyamide 6
Authors: Yoshikawa K. , Molnár A. , Eisenberg A. 
Published: May 2005

AbstractDynamic viscoelastic properties of blends of alkali metal salts of sulfonated polystyrene ionomers with polyamide 6 were investigated in the melt. The blends of lithium‐sulfonated polystyrene (10 mol% sulfonation) with polyamide 6 (LiSPS/PA‐6) behaved as a homogeneous viscoelastic fluid over most of the blend composition range, since blending with PA‐6 disrupted the ionic network of the LiSPS. Specific interactions between the lithium sulfonate group and the amide group are believed to be responsible for the behavior. By contrast, blends of sodium‐sulfonated polystyrene with PA‐6 (NaSPS/PA‐6) showed typical behavior of immiscible systems in that they exhibited large positive deviations from the log‐additivity rule for complex viscosity. This implied that sodium sulfonate groups did not interact strongly with amide groups, in contrast to the behavior of lithium sulfonates. Oldroyd's emulsion model was applied to the results of dynamic viscoelasticity studies of both the immiscible ionomer/PA‐6 blends and the polystyrene/PA‐6 blends. For the latter, the fit was much better than for the former. This difference in behavior might be due to partial miscibility or to the presence of an indistinct phase boundary in the “immiscible” ionomer‐based systems.
Electrical resistivity behavior of mold‐cast metal‐filled polymer composites
Authors: Yang Lei , Schruben Dale L. 
Published: May 2005

AbstractMold‐cast, metal‐filled composites made of poly(methyl methacrylate) and aluminum or nickel exhibited electrical resistance qualitative behavior as predicted by the percolation and tunneling mechanisms. A precipitous change in resistivity of about 104 ohm‐cm was found at volume concentrations of filler in the range of 18.5 to 19.8 vol%. Details of the electrode system are given for making these measurements. Using different polymers does not change the resistance behaviour of the composite to any great degree, suggesting that particle features of shape, size, arrangement, and so forth are the more important parameters. Such particle morphological details are indicated in the included photomicrographs.
Extension of effective medium theory to three‐component system—two conductive particle types in the polymer matrix
Authors: Trivedi A. H. , Garcia J. , Burhan A. B. , Schruben D. L. 
Published: May 2005

AbstractA foundation is presented for the extension of the normal effective medium theory (for a two‐component system (filler and polymer matrix)) to a three‐component system (two filler species and matrix). No experimental test of the improved theory is made here, but some general trends are confirmed by other experiments. The theory is sufficiently general to allow the second filler component to represent a particle of the same composition as the first filler component but of a different size, or of the same size but of a different composition. Important satellite derivations are included.
Shrinkage modeling of polyester shrink film
Authors: Shih Wayne K. 
Published: May 2005

AbstractA model was developed to quantify the thermal shrinkage behavior of polyester shrink film under isothermal and nonisothermal conditions. This model employs the straightforward first order reaction kinetics to an otherwise microscopically complex relaxation process. It offers three unique parameters for quality control and material specification of shrink film. In the isothermal condition, the induction time, the shrink constant, and the ultimate shrinkage are the three parameters used by the model to quantify the shrinkage of shrink film under an elevated but constant temperature. In the nonisothermal condition, the shrink film is heated using a constant heating rate. Three parameters, which are the onset shrink temperature, the shrink constant, and the ultimate shrinkage, characterize the shrinkage of shrink film. The model fits the experimental data very well. The thermal shrinkage of several polyester homopolymers, copolymers, and polyester blends was investigated and compared to that of poly(vinly chloride) (PVC) shrink film. Two polyester blends containing glycol modified poly(ethylene terephthalate) (PETG) copolyester behave similar to PVC in shrinkage behavior. The effect of stretch temperature, stretch ratio, and stretch rate on the shrinkage characteristics of oriented PETG film was also studied. The stretch temperature has the highest influence on the shrinkage behavior of oriented film.
Polymer blends of polyethersulfone with all aromatic liquid crystalline co‐polyester
Authors: Yazaki Fumihiko , Kohara Atsushi , Yosomiya Ryutoku 
Published: May 2005

AbstractPolymer blends of polyethersulfone (PES) with an all aromatic liquid crystalline co‐polyester (LCP) were investigated. In addition, PES oligomers with the reactive functions end groups (−ONa) were added as a third component to the above blends in order to improve their properties. Flexural properties, such as modulus and strength, and dynamic viscoelastic properties, such as dynamic storage elasticity (E′) and loss tangent (tan δ), of the blends were measured. The morphology of blends was characterized using a differential scanning calorimeter (DSC) and a scanning electron microscope (SEM). Of the flexural properties, the modulus of PES increased almost linearly with increasing LCP content. However, strength decreased as LCP content increased to 20 wt%. In contrast, the addition of the PES oligomers had little effect on modulus, but strength was clearly improved. Regarding dynamic viscoelastic properties, the oligomer‐containing blends exhibited complex behavior. Regarding morphologies, SEM analysis revealed that the LCP was not fibrous in the core of the blend containing 40 wt% or less, but the addition of the PES oligomers made LCP fibrous even in blends with low LCP content. It was concluded that the PES oligomers with reactive functional groups acted as a compatibilizer in polymer blends of PES/LCP.
Generation of microcellular polymeric foams using supercritical carbon dioxide. II: Cell growth and skin formation
Authors: Goel Satish K. , Beckman Eric J. 
Published: May 2005

AbstractWe have generated microcellular polymeric foam structures using a pressure induced phase separation in concentrated mixtures of supercritical CO2 and poly(methyl methacrylate). The process typically generates a microcellular core structure encased by a nonporous skin, the thickness of which decreases with increasing saturation pressure. This trend can be described by a model for skin formation that is based on the diffusion rate of gas out of the sample. Significant density reductions on the order of 30 to 70% can be achieved by changing the pressure and temperature conditions in the foaming process. There are several ways in which the saturation pressure affects the average cell size, with the net effect that cell size decreases sharply with increasing pressure above 2000 psi, leveling out at higher pressures. Cell size increases with increasing temperature from 40°C to 70°C. A model for cell growth, based on a cell model of Aremanesh and Advani, modified to include the effect of CO2 on model parameters, reproduces these trends.
Experimental study of transcription of minute width grooves in injection molding
Authors: Yoshii Masaki , Kuramoto Hiroki , Kato Kazunori 
Published: May 2005

AbstractIn injection molding of substrates for optical discs, precise transcription of pits and grooves is very important. For high‐density optical discs, molding transcription for minute grooves with widths on the sub‐micron level is required. In this paper, in order to clarify the relationship between molding conditions and transcription quantitatively, transcription of minute rectangular grooves (width 0.55 μm, depth 70 nm) in injection molding of polycarbonate resin was studied. The relationship between molding conditions and the transcription heights was verified. And, by introducing the equivalent thickness of the vitrified layer concept, a transcription model related to the minute groove width is proposed. This equivalent thickness of the vitrified layer is estimated to be 100 to 150 nm at the point of filling completion under a certain molding condition. Also, using the above description of the equivalent thickness of the vitrified layer, it is possible to estimate the extent of transcription under the various molding conditions.
Reaction‐induced phase separation during the formation of a polyurethane‐unsaturated polyester interpenetrating polymer network
Authors: Chou Y. C. , Lee L. J. 
Published: May 2005

AbstractIn this study, an interpenetrating polymer network (IPN) based on a polyurethane (PU) and a partially end‐capped unsaturated polyester (UPE) was prepared. The reaction‐induced phase separation process of the IPN was studied using a phase contrast optical microscope and a transmission electron microscope (TEM), while reaction kinetics and onset of gelation were determined by a differential scanning calorimeter and a rheometer respectively. Except at low temperatures, the phase separation patterns were found to follow the spinodal decomposition mechanism. An interconnected phase developed quickly and was followed by coalescence of the periodic phase to form droplet/matrix type of morphology. A second level of phase separation also occurred within both the droplet and the matrix phases in some cases. The domain sizes resulting from both levels of phase separation gradually increased until the structure was locked by chemical gelation. Reaction temperature, PU reaction rate, and UPE reaction rate all had significant effects on the final morphology of the formed IPNs.