bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isothermal gas‐assisted displacement of viscoplastic liquids in tubes
Authors: Poslinski A. J. , Oehler P. R. , Stokes V. K. 
Published: May 2005

AbstractIsothermal experiments on gas‐assisted displacement of viscoplastic liquids in tubes show that a liquid coating remains on the tube wall. The thickness of this coating approaches 0.35 of the tube radius at high gas penetration rates, the asymptotic limit previously observed for Newtonian liquids. At low gas penetration rates, the viscoplastic coating is much thinner than its Newtonian counterpart. During the displacement process, the gas front moves faster than the liquid front and, prior to blowout, it rapidly accelerates as the amount of liquid downstream of the gas is depleted by the liquid coating. Based on these observations, a simple isothermal model is developed to describe the gas‐liquid dynamics. This model provides an insight into the gas‐assisted injection molding process in which the injection of molten plastic into a mold is assisted by a pressurized gas. In particular, the results show that the wall thickness around the hollow cores in gas‐assisted parts is set during processing by the solid skin and a thick molten layer. The thickness of the molten layer depends on the gas penetration rate and the viscous behavior of the molten plastic. By coupling the isothermal model with a one‐dimensional heat‐transfer analysis, the gas penetration rate is shown to be several orders of magnitude higher than the plastic freezing rate, so that most of the heat transfer between the melt and the gas occurs after the mold is filled.
Crystal orientation and twinning in cold‐rolled ultrahigh molecular weight polypropylene
Authors: Hibi Sadao , Niwa Takahiro , Mizukami Jun , Wang Chi , Kyu Thein 
Published: May 2005

AbstractThe mechanisms of plastic deformation in cold‐rolled ultrahigh molecular weight polypropylene (UHMWPP) have been explored by means of wide angle X‐ray (WAXD) pole figures. The melt crystallized UHMWPP slabs were rolled unidirectionally in a two‐roll mill at 408 K as well as in the cross (transverse) direction. In the unidirectional rolling, all reciprocal lattice vectors of (110), (040), and (130) were found to orient preferentially in the film normal (thickness) direction. The cross‐rolling of UHMWPP shows the preferential orientation of the above plane normals in the film thickness direction, but the distribution of poles broadens toward the transverse direction. Such orientation behavior is very different from that of conventional cold‐rolled polypropylene. Various orientation mechanisms involving the orientation of lamellae in the film plane, twinning of the (110) plane and slippage mechanisms have been taken into consideration to account for the observed pole figures. A theoretical simulation has been carried out based on an orientation distribution function approach by introducing a slippage angle along the maximum shear stress in conjunction with intralamellar slip around the transverse direction. This model simulation conforms closely with the experimental WAXD pole figures of the (110), (040), and (130) planes.
Mechanical properties of polyurethane‐unsaturated polyester interpenetrating polymer networks
Authors: Chou Y. C. , Lee L. J. 
Published: May 2005

AbstractInterpenetrating polymer networks (IPNs) based on a polyurethane (PU) and two unsaturated polyester (UPE) resins (a commercially available UPE and a partially endcapped UPE) were prepared. The mechanical properties, such as tensile strength, elongation at break, impact strength, and dynamic mechnical properties of IPNs, were studied by changing reaction temperature, PU reaction rate, and UPE reaction rate. Owing to the unique microgel formaton of UPE, the first formed network tends t be the dispersed phase in the PU‐UPE IPN system. The reaction sequence was found to be an important factor in determining the phase mixing and phase morphology of the IPNs. When the PU reaction was faster, extensive phase mixing due to strong grafting or chain interpenetration was obtained. When the UPE reacted first, grafting was retarded by the microgel formation of the UPE network. It was found that simultaneous reaction of the two reacting system resulted in a co‐continuous structure that provided enhanced tensile properties and impact strength.
Water adsorption at a polyimide/silicon wafer interface
Authors: Wu Wen‐Li , Orts William J. , Hunston Donald L. , Majkrzak Charles J. 
Published: May 2005

AbstractNeutron reflectivity (NR) was applied to measure te concentration of water at the buried interfaces between an amorphous poltimide and silicon single crystal wafers. Excess water was discovered within 30 Å of the metal/polymer interface, where the water concentration reached 17% (by volume) for the samples without a coupling agent and 12% for the ones with coupling agent. Beyond the interface, the water concentration was measured at2 to 3%, which is typical of bulk polyimide. The above results demonstrate conclusively the unique power of NR in determining water concentration near a buried interface, and provide the first quantitative evidence for a water concentration profile which peaks in the interface region.
Dynamic simulation of flow‐induced fiber fracture
Authors: Yamamoto Satoru , Matsuoka Takaaki 
Published: May 2005

AbstractA dynamic simulation method has been developed of the fracture process of a fiber in a flow field using the particle simulation method proposed i a previous paper. The fiber is modeled with bonded spheres as a fiber model. The flexibility of the fiber model is altered by changing three parameters of the stretching, bending, and twisting constants between adjacent spheres. The stress induced in each bond of the fiber model as a result of deformation is formulated using displacement of the bodn distanc, bond angle, and torsion angle fr each pair of spheres. After deformation, the fiber model fractures at the bond at which the stress surpasses the strength of the fiber. The motion of the fiber model in a flow field is determined by solving the translational and rotational motion equations for individual spheres under the hydrodynamic force and torque exerted on them. The correctness of the method and formulation was verified by comparing the simulated deflection curve of a cantilever beam (with a concentrated load at the end) with the theoretical curve. Good agreement was found in both the deflection and slope of the beam. The fracture process of a fiber after bending deformation in a two‐dimensional siimple shear flow was simulated under assumptions of an infinitely dilute system, no hydrodynamic interaction, and a low Reynolds number of a particle. The calculated critical conditions of the flow field for fiber fracture were compared with Forgacs and Mason's theoretical ones. Simulated values of the fracture condition of the fluid shear stress related to the Young's modulus of a fiber agree with theoretical ones over an aspect ratio of 15.
Measuring the viscoelastic properties of an ethylene4‐tetrafluoroethylene copolymer at ultrasonic frequncies
Authors: Thomas V. , Giacomin A. J. , Wolfenden A. 
Published: May 2005

AbstractSince poly(tetrafluoroethylene) (PTEE) and its copolymers are soluble only at high temperatures in primarily perfluorocarbon solvents, direct measurement of their molecular weight distribution by conventional dilute solution techniques is not possible. Instead, the structure must be inferred from the linear viscoelastic properties of the melt. To make this inference, the spectrum must be determined over a wide enough range of relaxation times t include the plateau modulus, G. This is accomplished by time‐temperature superposition for most polymers. For PTFE and its copolymers, the range between the melting point and th degradation temperature is too narrow for time‐temperature superposition to be used reliably for determination of the high frequency response. Hence, as they do not exist in the melt state over a wide enough temperature range for superposition, their viscoelastic properties at high frequencies must be measured directly. A new technique employing a piezoelectric ultrasonic composite oscillator has been developed. The viscoelastic Properties, G′(ω) and G″(ω), of Tefzel 280 (a high molecular weight ethylene‐tetrafluoroethylene copolymer) have been measured at ultrasonic frequencies (40 to 200 kHz).
Morphology and mechanical properties of epoxy resins containing functionalized perfluoroether oligomers
Authors: Mascia L. , Zitouni F. , Tonelli C. 
Published: May 2005

AbstractChain extended perfluoroether oligomers were found to be miscible with bisphenol epoxy resins at all concentrations. These were evaluated as modifiers for anhydride cured resin systems, taking advantage of the carboxylic acid functionality at the chain ends. By altering the mixing and curing procedure different two‐phases morphologies could be obtained varying from fine co‐continuous networks, which produced transparent castings, to opaque systems consisting of precipitated heterogeneous particles. While the Tg and flexural modulus were found to be slightly lower than the control cure resin, the addition of the fluoroligomer modifier produced large increases in flexural strength, ductility, and fracture toughness. Samples with an IPN type morphology were found to exhibit an increase in ductility after aging at 200°C for three weeks proportionally to the concentration of fluoroligomer used.
Influence of processing on quality of injection‐compression‐molded disks
Authors: Yang S. Y. , Ke M. Z. 
Published: May 2005

AbstractA modified injection molding machine with a compression mechanism, and a mold with a movable wall and shut‐off mechanism, were used to investigate the effects of processing parameters on the quality of injection‐compression‐molded polystyrene disks. The compression start‐up time, compression force, melt temperature, and part thickness were selected processing parameters. The disk moldings were evaluated based on dimensional accuracy and birefringence. It is found that the compression start‐up time affects packing time, and thus greatly affects the residual orientation. If the transition from packing to compression could start before peak cavity pressure, disks with low residual orientation could be obtained. High compression force improves part quality and reduces thickness. Since both compression‐induced reduction and cooling‐induced shrinkage are involved, the effects of temperature and thickness are not as straightforward as the trends in conventional injection molding.
Experimental and theoretical studies of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts
Authors: Chang R. Y. , Tsaur B. D. 
Published: May 2005

AbstractAn integrated theory and computer program were developed in this study for simulation of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts. The basic theory considers the following items: (1) mold cooling analysis; (2) analysis of the polymeric filling, packing, and cooling processes; (3) viscoelastic behavior of polymeric fluid; (4) influence of thermal and mechanical properties of polymer; (5) pressure‐volume‐temperature relationship of polymer; (6) crystallization kinetics of crystalline polymer; and (7) solid mechanics analysis. Considered are the origins of defects, e.g. nonuniform cooling process, nonuniform volume shrinkage, flow‐induced residual stress, thermal induced residual stress, and crystallization behavior. The boundary element and the finite difference method were applied toward calculating the mold cooling analysis for obtaining the temperature profile at the cavity surface as the boundary conditions in filling and packing analysis. A hybrid finite‐element and finite‐difference methods were employed for simulating the injection molding filling, packing, and cooling processes. A control volume method was applied towards both finding the melt front position and also calculating the temperature and pressure profile at any instant during the filling process. A modified Tait equation provided a description of the pressure‐volume‐temperature relationship of crystalline polymers. The Malkin's kinetics model was employed to describe the behavior of polymer crystallization. The flow‐induced and thermal induced‐residual stresses employed as the initial conditions in the solid mechanics analysis were obtained with the linear thermo‐viscoelastic model. The displacements, including the thickness direction of part, which could not be calculated by the traditional bending moment method, were solved by using the numerical solid mechanics analysis with the three dimensional finite element method. These methods were applied to predict the shrinkage, warpage, and sink marks of crystalline polypropylene and amorphous ABS for the plate cavity. Both the qualitative results for the theoretical prediction correlated sufficiently with the experimental data. The theoretical results were also correlated using the commercial software C‐MOLD.
Predicting mechanical properties of acrylonitrile‐butadiene‐styrene terpolymer in injection molded plaque and box
Authors: Kim B. H. , Hwang T. W. , Park Hern Jin 
Published: May 2005

AbstractA methodology to predict mechanical properties in injection molded parts has been developed. Knowledge of part properties before actual molding and testing will be of immense help to part and mold designers in modification of design. This methodology involved the application of connectionist learning systems, injection molding computer simulation, and experimental evaluation of mechanical properties, to relate the thermomechanical history of injection molded parts to the resulting part properties of injection molded parts are dependent upon their thermomechanical history which in turn is greatly influenced by the processing conditions and part geometry. As the relationships between engineering properties and thermomechanical history are complex and highly nonlinear, the methodology developed was based on a backpropagation neural network algorithm that provided the means for a nonparametric mapping between the part properties and thermomechanical history. The proposed methodology has been successfully applied to two geometries, plaque and box. This methodology provides designers with the ability to predict mechanical properties in injection molded parts when significant thermomechanical history can be obtained from injection molding simulation.
Free radical polymerizations associated with the trommsdorff effect under semibatch reactor conditions. I: Modeling
Authors: Ray Asit B. , Saraf D. N. , Gupta Santosh K. 
Published: May 2005

AbstractSeveral important polymerizations [e.g., poly(methyl methacrylate) (PMMA), polystyrene] exhibit gel and glass effects during polymerization. These are associated with the decrease of the diffusivities of the macroradicals and monomer molecules with increasing viscosities of the reaction mass. A new model has been developed to account for the gel and glass effects, both under batch and semibatch reactor operations. The free volume theory of Vrentas and Duda has been used to account for the changes in the diffusion coefficients. The model parameters are tuned using experimental data on the isothermal bulk and solution polymerizations of MMA in batch reactors. Conversion histories and molecular weights have been obtained for cases where solvent, initiator or monomer are added to (or removed from) the reaction mass after some reaction has taken place. In addition, studies involving step changes in temperature hav been carried out. It is found that the conversion vs. time behavior after such step changes depend upon a complex interplay of three factors: Polymer concentration, molecular weight, and the temperature at the point these changes are effected.
Novel diagnosis of thermal deterioration for organic insulating resins by optical loss analysis
Authors: Takezawa Yoshitaka , Akasaka Shin‐Ichi , Koyama Tohru , Miya Hisaichi , Shimodera Makoto 
Published: May 2005

AbstractWe propose an “optical loss analysis” as a novel nondestructive diagnosis for the thermal deterioration of insulating resins. Using an alkyd resin film, the optical absorptin loss per unit optical path length and the glass transition temperature (Tg, DMA) by dynamic mechanical analysis were measured during heating tests. At longer heating times, values of the optical absorption loss and the Tg, DMA increased concurrently. By rescaling the heating time as a reduced time as a reduced time, a master curve of the deterioration for the resin was obtained. Consequently, when thermal stress is the main cause of the deterioration, one can estimate the degree of deterioration and theoretically the residual lives of resins using this optical loss analysis.
On the measurement of residual stress in plastic pipes
Authors: Clutton E. Q. , Williams J. G. 
Published: May 2005

AbstractRecent work on the determination of residual stress in drawn pipes has revealed an error in previous methods used. Such pipes have residual stresses very different from those induced by melt extrusin during conventional pipe processing. In particular, it appears that there are considerable compressive stresses at the bore, and the hoop and axial values are not equal. In an attempt to measure these values, tests were performed on slit rings of varying length, and a pronounced dependence of ring overlap on length was observed. This was contrary to previous assumptions, and a corrected version of the analysis has been developed, which enables the true hoop and axial stresses to be determined by testing rings of various lengths. For isotropic pipes, it has been shown that hoop and axial stresses are roughly equal. Previous results obtained on thin pipe rings can now be corrected by multiplying by the factor 1/(1‐v). For anisotropic drawn pipes, a combination of rings and thin axial strips is used to determine the residual stresses. These pipes can show remarkably low stresses at the bore, which may play a significant part in determining their performance.
Mechanism of flame retardant action of red phosphorus in polyacrylonitrile
Authors: Ballistreri A. , Montaudo G. , Puglisi C. , Scamporrino E. , Vitalini D. , Calgari S. 
Published: May 2005

AbstractThe mechanism of flame retardant (FR) action of red phosphorus in polyacrylonitrile combustion was investigated by thermogravimetry, flash‐pyrolysis GC‐MS, and combustion methods. Red phosphorus was found to increase the thermal stability in air of polyacrylonitrile and to induce a char residue increment on this substrate. Both these effects disappeared when pyrolysis was carried out under nitrogen flow. Flash‐pyrolysis GC‐MS experiments showed that red phosphorus does not alter the pyrolysis product distribution of polyacrylonitrile, which implies that there is no specific interaction between polyacrylonitrile and red phosphorus. These data also showed that polymeric red phosphorus decomposes to volatile white phosphorus (P4) during pyrolysis. These observations allow us to propose a simple model for the mechanism of FR action of red phosphorus on polyacry‐lonitrile at the molecular level. Combustion data for polyacrylonitrile‐red phosphorus mixtures are in agreement with the proposed mechanism of FR action.
Aging effects on fire‐retardant additives in polymers
Authors: Clough R. L. 
Published: May 2005

AbstractExtensive thermal aging experiments have been conducted on (i) ethylene‐propylene rubber (EPR) formulations containing various commercial halogenated‐hydrocarbon fire‐retardant additives together with Sb2O3, and (ii) on chlorosulfonated polyethylene (CSPE) formulations with and without added Sb2O3. Significant losses of both chlorine and antimony are found on aging, dependent upon the ability of the particular halocarbon to undergo intramolecular dehydrohalogenation. The stoichiometry indicates antimony volatilization as SbCl3. Arrhenius treatment of the data for the EPR formulation which undergoes the most rapid loss gives an overall activation energy of 34 kcal/mol for antimony volatilization and indicates that fire‐retardant loss should become appreciable only at temperatures significantly above ambient (i.e., 70°C). Oxygen index flammability measurements showed moderately increased flammability for certain aged EPR samples, but showed significantly decreased flammability for aged CSPE which was correlated with the loss of other volatile components from the formulation.
Block copolymerization of 3,3‐dimethyl‐2‐oxetanone. II. Synthesis of polydimethylsiloxane‐containing copolymers
Authors: Lefebvre P. M. , Jérôme R. , Teyssié Ph. 
Published: May 2005

AbstractCarboxy‐terminated polydimethylsiloxanes (PDMSs) have been prepared by anchoring the functional end group on the main chain via a hydrolytically stable SiC bond. The neutralized carboxy‐terminated PDMSs are effective initiators of the 3,3‐dimethyl‐2‐oxetanone (or pivalolactone) block copolymerization. The yield of block copolymers depends on the initiation efficiency of the carboxylate end groups, but this limit can be overcome by the use of more than one carboxylate group per end chain, and “palm‐tree” structures are obtained. The ability to crystallize of poly(3,3‐dimethyl‐2‐oxetanone) is significantly depressed when this polyester is engaged in PDMS‐rich block copolymers, but the observed heterophase morphologies (350 Å) are uniformly fine.
Properties of polyimide films doped with copper complexes
Authors: Ezzell S. A. , Furtsch T. A. , Khor E. , Taylor L. T. 
Published: May 2005

AbstractPolyimide films based on either 3, 3′, 4, 4′‐benzophenone tetracarboxylic acid dianhydride or pyromellitic dianhydride with 4,4′‐oxydianiline have been doped with copper(I) and copper(II) complexes. High‐quality, flexible, glass‐cast films have been obtained which exhibit increased softening temperatures and lower polymer decomposition temperatures. The atmosphere and glass sides of the films are quite different. The copper(I) dopant is oxidized on the air side of the film, while the glass side contains predominantly copper (I). In the copper(II) case most of the copper appears on the air side as a silvery substance in the Cu(II) state. Chemical as well as ion etching can remove this material. Electrical resistivity of the copper(II)‐doped films is decreased by three to five orders of magnitude relative to the polymer alone.
Polyimides and polyamides with semiflexible spacers
Authors: Evans John R. , Orwoll Robert A. , Tang Stephen S. 
Published: May 2005

AbstractThirteen polyimides and three polyamides were synthesized with alternating rigid and semiflexible polymethylene units along the chain backbone. Derivatives of the pyromellitic species served as rigid segments in the polyimides and the sulfanilamide group was incorporated in the rigid segments of the polyamides. These systems were examined for a thermotropic liquid–crystalline phase. None was detected, probably because of the high crystalline melting temperatures of these polymers.