bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear low density polyethylenes and their blends: Part 4 shear flow of LLDPE blends with LLDPE and LDPE
Authors: Utracki L. A. , Schlund B. 
Published: December 2004

AbstractThe steady state and dynamic shear behavior of linear low density polyethylenes (LLDPE) blended with low density polyethylene (LDPE) and with another LLDPE resin were measured in capillary and parallel plate geometries at T = 150, 190, and 230°C. The extrudate swell and the Bagley correction were determined. It was observed that the pressure correction plays a significant role in capillary flow of LLDPE/LDPE blends–an indication of immiscibility. Several other rheological functions also suggested a phase separation for the system. Nevertheless, the blend behaved as a “compatible” mixture of emulsion type. By contrast, blends of two LLDPE resins show expected miscibility. However, even in this case additivity was not always observed. A new simple method of calculating the relaxation spectrum was developed. The method is analytical and its accuracy depends on adequacy of the semiempirical relation (proposed previously) to describe dynamic viscosity dependence on the test frequency. For all samples the spectrum allowed computation of storage modulus in good agreement with experimental findings.
Light‐scattering characterization of polyblends in the presence of multiple‐scattering conditions
Authors: Cielo P. , Favis B. D. , Maldague X. 
Published: December 2004

AbstractA novel approach is described for the noncontact evaluation of structural morphology in polyblends by light scattering. Optical methods are attractive for the on‐line characterization of translucent materials because they are noninvasive, rapid, and applicable to high temperature materials. One limitation of conventional light‐scattering techniques is their requirement for relatively thin samples in order to avoid multiple‐scattering effects that smear out the details of the light diffraction pattern. The approach described in this paper is meant to circumvent this limitation by resorting to turbidimetric measurements, which provide useful information on the average size, shape, concentration, and orientation of the dispersed phase particles even in the presence of multiple scattering. The sample thickness is no longer restricted, and methods are described by which the near‐surface volume of infinitely thick parts may be inspected with access to a single side of the material. Results are presented for polypropylene‐polycarbonate (PP/PC) samples of different thicknesses and microstructural morphology, including fibrillar‐type oriented structures.
A modeling of semibatch reactors for melt transesterification of dimethyl terephthalate with ethylene glycol
Authors: Choi K. Y. 
Published: December 2004

AbstractA mathematical model of a semi batch reactor was developed to investigate the oligomerization reactions in the melt transesterification of dimethyl terephthalate with ethylene glycol catalyzed by metal acetate catalyst. The detailed kinetic scheme based on the molecular species model is used to estimate the conversion of methyl ester groups and the concentrations of various oligomeric species. The numerical simulation of the model shows that the oligomerization reactions lower the overall conversion of methyl ester end groups. Effects of ethylene glycol/dimethyl terephthalate mole ratios, reaction temperature and, catalyst concentration on the conversion, oligomer concentration, oligomer molecular weight, and molecular weight distribution were also analyzed.
Formation of diethylene glycol by dehydration of glycol in the presence of terephthalic acid
Authors: Yamada Toshiro 
Published: December 2004

AbstractThe amount of diethylene glycol (DEG) formed as a result of the dehydration reaction of ethylene glycol (EG) in the presence of terephthalic acid (TPA) was measured. It became clear that the amount of DEG formed at the boiling point of EG can be expressed by a regression equation. It was confirmed that by this equation, the amount of DEG formed under the carboxylic end group concentration of 0.0 to 0.6 Eq/kg and the reaction time of 0 to 20 h can be estimated with high accuracy.
Strength properties of melt blown nonwoven webs
Authors: Choi K. J. , Spruiell J. E. , Fellers J. F. , Wadsworth L. C. 
Published: December 2004

AbstractA method to obtain the tenacity and Young's modulus of nonwoven webs without direct measurement of web thickness is proposed. This has been tested with several series of samples with different basis weight. It was found that these properties were nearly Independent of the sample gage length, and both tenacity and modulus generally decreased with increase in the die temperature, the air pressure at the die, or the die to collector distance [DCD]. The web stiffness as measured by bending rigidity followed similar trends. The elongation Lo break also decreased as die temperature and air pressure at The die increased, but it increased with increasing DCD. The average filament diameter in the web decreased with increasing die temperature or air pressure at the die. The single filament strength was measured and compared with strength properties of web and of high‐speed melt spun filament prepared from the same resins. The strength of single filaments in the web lie in between those of the web and high‐speed spun filaments. The mechanical properties of melt blown web were interpreted in terms of the changes in Fiber diameter, the level of interfilament bonding, the molecular orientation developed in the filament, the diameter uniformity along the individual filaments in the web, and the presence of voids in the filament.
Relation between characteristics and melting point of oligomers in poly(ethylene terephthalate) manufacturing
Authors: Yamada T. , Imamura Y. 
Published: December 2004

AbstractThe applicable range of the regression equation proposed by Yamada, et al. expressing oligomer melting point by oligomer characteristics and relations derivable from the equation correlating each oligomer characteristic and melting point were studied. It was confirmed that the equation is applicable not only to poly(ethylene terephthalate) (PET) oligomer but also to the extent of polymerization. As number‐average degree of polymerization (Pn) increases, the influence of end groups on melting point becomes weak, and when Pn exceeds 50, the influence of end groups becomes negligibly small. On the other hand, when Pn is below 2, It was confirmed that the influence of end groups on melting point is very strong.
Numerical simulation of reactive injection molding in a radial flow geometry
Authors: Lack C. D. , Silebi C. A. 
Published: December 2004

AbstractThe radial flow of a chemically reactive fluid between two parallel circular disks during the process of Reactive Injection Molding (RIM) has been simulated in a decelerative, non‐isothermal, transient flow environment. The effects of key operating and system parameters (feed temperature, volumetric flow rate, reaction rate, and cavity thickness) on velocity, conversion, and temperature profiles which occur in this decelerative flow environment were determined. A catalyzed, unfilled polyurethane RIM system was modeled by a linear step polymerization scheme using average literature values for the reaction rate, and thermodynamic and constitutive parameters. The numerical solution was achieved using the method of lines and upwind approximations of the spatial derivatives. The geometry studied (two parallel, center gated circular disks) models flow patterns in commercial RIM processes more realistically than the rectangular flow between two parallel surfaces (studied by previous workers) in which the average velocity is constant along the length of the mold. This simulation predicts the accumulation of high polymer near the entrance to the mold and near the outer edge of the cavity in fast reactive systems. The accumulation of material near the gate results in viscous heat generation and a maximum in temperature in the region immediately downstream from the restriction.
Extrusion behavior of filled polymeric systems exhibiting an apparent yield stress
Authors: Poslinski A. J. , Ryan M. E. , Gupta R. K. , Seshadri S. G. , Frechette F. J. 
Published: December 2004

AbstractAn investigation was undertaken to study the extrusion behavior of composite systems. A compound made up of approximately 50 percent ceramic particulates by volume dispersed in a high molecular weight thermoplastic polymer was characterized by measuring the shear viscosity on an Instron capillary viscometer. The experimental data indicated that the ceramic composite exhibited an apparent yield stress. As a result, an expression that was previously shown to provide flexibility for describing a yield stress at low rates of deformation could explain the viscosity of the ceramic composite. The expression was then applied to the flow analysis of both a “rod” and a “slit” die in an extrusion process, and the derived equations adequately correlated experimental volumetric flow rate us. Pressure drop data obtained on a laboratory extruder.
The effect of sizing on composite properties for materials used in the shuttle filament wound case
Authors: Cagliostro D. E. 
Published: December 2004

AbstractAn epoxy resin and a sized carbon fiber have been used to produce a light‐weight filament wound case for the Space Shuttle. The sizing facilitates fiber handling during winding but may affect the amount of resin absorbed by the fiber during impregnation and the final mechanical properties of the composite. Naval Ordnance Lab rings were wound to study the effect of the sizing content on the resin absorption by the fiber bundles, the final tensile properties of the composite, and the type of failure observed at burst. The resin content of the rings studied was between 20 to 40 percent, and the sizing content, 0 to 1.6 percent by weight. Results showed that the sizing content was a critical parameter which determined the amount of resin absorbed by the fibers. The final tensile strength was dependent on the amount of sizing present. The tensile strength decreased by as much, as 60 percent when a low resin and high sizing content were present. The type of failure at burst was a function of resin content rather than size content.
The mechanical behavior of polymer coatings: Solvent removal in polyamic acid films
Authors: Bauer Charles L. , Farris Richard J. 
Published: December 2004

AbstractThe development of the mechanical properties and stresses during the formation of polyamic acid (PAA) coatings has been studied using methods such as a “propagating wave technique.” The shrinkage stress due to solvent removal in PAA coatings under a one dimensional constraint was determined to be 8 MPa. A coupling between the residual stress and solvent removal process has been observed.
Process control of profile extrusion using thermal method. Part I: Mathematical modeling and system analysis
Authors: Yang B. , Lee L. J. 
Published: December 2004

AbstractAn analytical model based on the heat penetration through the die wall was preposed to calculate the effect of die wall temperature on the flow of polymer melt in profile dies. Model prediction matched well with the experimental data measured from a modified Instron capillary rheometer. The model was applied to an extrusion line with an L‐shaped profile die. Dynamic responses of the profile extrusion line based on this die were measured and modeled. The pairing of manipulated variables and controlled variables was analyzed.
Residual stresses in polymeric passivation and encapsulation materials
Authors: Noyan I. C. , Nguyen L. T. 
Published: December 2004

AbstractThe residual stresses caused by polyiinide (Pi 5878 and PI 2566), and silieone (3‐6550 and 1‐2577) films used as passivation/encapsulation layers in microelectronic circuit manufacturing are investigated by X‐ray curvature measurements. For both PI types, the maximum stress is between 20–40 MPa. This stress is independent of film thickness for films thinner than 10 μm. For films thicker than this value, however, some dependency of the film stress on film thickness is observed. The variation of stress during the cure cycle is significantly different for PI 5878 and PI 2566. This is due to void nucleation and growth in the 5878 films during solvent volatilization. The silieone films have no residual stress at room temperature for all thicknesses. The compensating stresses in the Si wafer are insignificant for all cases studied.
Lateral strain effects during the large extension of thermoplastics
Authors: Stokes Vijay K. , Nied Herman F. 
Published: December 2004

AbstractA noncontacting experimental procedure is used for characterizing lateral strain effects during the large‐strain uniaxial stretching of flat sheet‐like specimens of polycarbonate, polyetherimide, and poly(butylene terephthalate), both at room and elevated temperatures. It is shown that the in‐plane lateral stretch, λ2, is related to the longitudinal stretch, λ1, through the relation λ2 = λ. Depending on the temperature, the “Poisson's ratio” for incremental strains, n, is shown to lie between n = 0.4 and n = 0.5. While the lateral stretch in the thickness direction, λ3, is smaller than λ2 at room temperature, it is shown that λ3 = λ2 at higher temperatures. Stretch data have been used to infer the volumetric strains in these materials.
Molecular orientation of polypropylene by rolling‐drawing
Authors: Tate K. R. , Perrin A. R. , Woodhams R. T. 
Published: December 2004

AbstractRolling‐drawing is a simple, effective, solid state processing technique for manufacturing high strength and high modulus oriented polymer sheet products. The process is capable of increasing the tensile modulus and strength of polypropylene by more, than an order of magnitude with inexpensive equipment and straight forward controllable techniques. This paper gives an overview of the rolling‐drawing of polypropylene. It is intended to answer the following questions. What is rolling‐drawing? What changes in tensile properties can be expected as a result of this process? What deformation processes occur during rolling‐drawing? What are the processing variables and how do these variables relate to the deformation ratio achieved by rolling‐drawing? A tensile flow stress relationship was formulated from experimental data for oriented polypropylene. This constitutive equation, estimates the flow stress (or yield stress) of the polymer as a function of deformation ratio, strain rate and temperature. Since stretching was found to provide a significant portion of the deformation during the rolling‐drawing process a Hoffman‐Sachs computer analysis was written to predict plastic deformation and drawing forces in the stretch zone. The results of experimentation and the analysis are briefly compared in this paper.
Evaluation of residual thermally induced stresses in the cooling of polymer melt via transfinite element computations
Authors: Tamma K. K. , Railkar S. B. 
Published: December 2004

AbstractThe present paper describes the evaluation of nonlinear thermally induced residual stresses in the cooling of polymer melt during injection molding of plastic components. The computational methodology adopted is based on the transfinite element approach, which is a hybrid scheme as it combines transform methods and classical Galerkin schemes with finite element formulations to preserve the modeling versatility. The applicability of the proposed formulations for understanding the physics and the nature of the nonlinear thermally induced stresses in the solidifying process of a sample amorphous polystyrene specimen demonstrates the basic capabilities and potential of the methodology. Results obtained agree qualitatively well with earlier research studies and experimental findings relevant to thermally induced residual stresses in the injection molding of plastic components.
On the accuracy of the calculated stress field around a craze
Authors: Warren W. E. , Chudnovsky A. , Mullen R. L. 
Published: December 2004

AbstractSeveral recent calculations of the stress field around crazes in glassy polymers have been based on experimentally obtained craze opening displacements. Although various techniques for performing these calculations have been presented (i.e., Fourier transform, boundary integral, and finite element methods), all are based on the solution of the same ill‐conditioned boundary value problem. Specific boundary conditions required to calculate the stresses around a craze lead to a large change in the stress field with small changes in the craze profile which are within the reported experimental tolerance.
Vitrification effect during the reaction injection molding (RIM) process of epoxy resin
Authors: Kim Do Hyun , Kim Sung Chul 
Published: December 2004

AbstractVitrification occurs during the reaction injection molding (RIM) of epoxy resin, and the curing reaction rate is reduced as the Tg of the reacting mixture exceeds or approaches the local reaction temperature inside the mold cavity. The effect will be manifested in the distribution of the glass transition temperature across the thickness direction of the molded product. The reaction kinetic equation which includes the vitrification term in the form of the WLF equation is used in the computer simulation of the epoxy RIM process and the effect of the vitrification is shown by comparing with models with no vitrification considerations.
The effect of mesh refinement on the computation of entrance effects for shear‐thinning fluids
Authors: Robichaud M. P. , Tanguy P. A. 
Published: December 2004

AbstractThe effect of mesh refinement on the finite element computation of velocity and pressure is assessed for the creeping flow of a power law fluid and a Carreau fluid through an axisymmetric sudden contraction. The emphasis is placed on the determination of the entrance pressure correction nent. The augmented Lagrangian formalism is used and the discretization of the variational problem is based on the Crouzeix‐Raviart triangular element. For power‐law fluids, it is found that fine meshes yield values of nent which are significantly lower than those obtained in previous numerical studies, especially for high shear‐thinning fluids. A similar trend is observed in the Carreau model.
The effect of extrudate swell on modeling the film blowing process
Authors: Seo Yongsok , Wissler Eugene H. 
Published: December 2004

AbstractThe extrudate swell effect has not received sufficient attention in modeling the film blowing process. This effect is addressed in this paper, and as an ab initio study, only viscous fluids were considered. The problem region was separated into two zones; the extrudate swell zone and the film blowing zone. The annular extrudate swell problem was solved using a finite element method. The film blowing process was modeled following Pearson and Petrie's (4) work. Although only viscous fluids were considered, the simulation results show a remarkable difference when swelling was included in the modeling. Viscoelastic fluids, which are more realistic for polymer melts, were not investigated here because of the so called high Weisenberg number problem. This is an open area still under investigation.
Measurement and correlation of mutual diffusion coefficients for polybutadiene‐hydrocarbon systems
Authors: Iwai Yoshio , Maruyama Shunsuke , Fujimoto Mitsuki , Miyamoto Shinji , Arai Yasuhiko 
Published: December 2004

AbstractThe mutual diffusion coefficients for polybutadiene‐ethylbenzene and polybutadiene‐n‐nonane systems were measured by using a sorption apparatus with a quartz spring in the temperature region from 80 to 130°C and for mass fraction of hydrocarbon ranging from 0 to 0.27. The mutual diffusion coefficients were correlated with good agreement by the free‐volume theory.
Effect of methylmethacrylate‐butadiene‐styrene modifier level on the viscoelastic beta process in poly(vinyl chloride)
Authors: Havriliak S. , Shortridge T. J. 
Published: December 2004

AbstractViscoelastic measurements were made on test specimens cut from plaques made from milled, compression molded blends of poly(vinyl chloride) (PVC) and methylmethacrylate‐butadiene‐styrene modifier (MBS). The experimental frequency range was from 0.0159 to 79.6 Hz. and the temperature range was from −140 to 20°C. The MBS modifier level studied was 8.26, 10.71, and 13.04 weight percent. This experimental range covers the beta relaxation process of PVC and the alpha relaxation process of the rubbery regions of the modifier. The complex compliance was represented in terms of a function originally proposed by Havriliak and Negami to represent the dielectric relaxation processes in polymers. The parameters of this expression as well as their dependence on temperature were determined by the multi‐response statistical techniques developed by Havriliak and Watts. Addition of MBS modifier to PVC appears to enhance the already present beta relaxation process in PVC. In addition the temperature dependence of the relaxation time has been increased so that the process is faster at room temperature. The α and β parameters of the relaxation function have changed so that the process is narrower at room temperature. There is no significant viscoelastic evidence supporting a second phase. This observation suggests significant impedance matching of the two phases which may be an important criteria for impact modification. Similarity of the two processes suggests a possible mechanism for the PVC beta process.
Water‐Soluble contrast enhancing materials—new photobleachable dyes
Authors: Yonezawa T. , Kikuchi H. , Hayashi K. , Tochizawa N. , Endo N. , Fukuzawa S. , Sugito S. , Ichimura K. 
Published: December 2004

AbstractMany styrylpyridinium compounds (SPC), which are very stable in the dark, were prepared and evaluated as photobleachable dyes for contrast enhanced lithography (CEL). The photobleaching characteristics of water‐soluble contrast enhancing materials composed of SPC and water‐soluble polymer depend on the structure of the SPC and the kind of polymers used. The technique using SPC‐based CEL proved to be very effective for the resist pattern profiles.
Effect of extensional and shearing strains on molecular orientation of a polymer melt
Authors: Picot J. J. C. , Santerre J. P. , Wilson D. R. 
Published: December 2004

AbstractThe flow of two grades of polydimethysiloxane (Dow Corning type 200 grades 60 Pa's and 300 Pa's) was studied in a 60° wedge flow cell. The stress‐optical law was validated along the center‐line (extensional strains only) and at off centerline locations (extensional and shearing strains combined). Values for stressoptical coefficient were 8.01 × 10−11 Pa−1 and 9.61 × 10−11 Pa−1 respectively, the differences apparently being due to experimental error. Orientation angles along a fixed radius at 20° to the cell center‐line were almost constant. Center‐line orientation angles were zero, as expected. Orientation angles at a constant radius for various angular positions varied from zero at the centerline to 54° near the wall. A method for testing constitutional relations for stress is presented. The power law model and linear viscoelastic models are shown to be inadequate in describing orientation effects caused by rotation in the flow. The Goddard‐Miller model was shown to express this but accuracy was not very good, perhaps because of the single Maxwell unit used.