bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of the feed section groove taper angle on the performance of a single‐screw extruder
Authors: Sikora Janusz W. 
Published: April 2004

AbstractA new mechanism is described that allows adjustment of the groove geometry in grooved feed extruders. This mechanism enables efficient, continuous and independent change of the groove geometry during the extrusion process. The patented solution of the activated grooved feed section enables one to change the number of grooves, taper angle and, connected with it, groove depth. The paper contains the graphical presentation of the selected results of experimental studies of autothermal extrusion of a medium density polyethylene in an extruder with the grooved feed section in which the groove taper angle, and thus groove depth, was changed during the extrusion process. The influence of changing the groove taper angle in the range from 0 to 5.236 × 10−2 rad and screw speeds ranging from 177 to 279 rev/min on extruder output was studied. The energy efficiency of the extruder was studied as well.
Effect of molecular weight on crystallization and melting of poly(trimethylene terephthalate). 1: Isothermal and dynamic crystallization
Authors: Wang Xue‐Song , Yain Deyue , Tian Guo‐Hua , Li Xin‐Gui 
Published: April 2004

AbstractThe crystallization behavior of poly(trimethylene terephthalate) as a function of molecular weight was investigated under isothermal and dynamic cooling conditions using a differential scanning calorimeter (DSC) and polarized light optical microscopy (POM). THe overall rate of bulk crystallization increased with molecular weight. An Avrami analysis of the isothermal crystallization kinetics indicated that the crystallization rate constant increased with increasing molecular weight. The Avrami exponent, n, approached 2 and was nearly independent of both molecular weight and temperature. The modified Avrami analysis developed by Jeziorny and Ozawa was applied to the dynamic crystallization data. At the same cooling rate, higher molecular weight resulted in a narrower crystallization peak, higher onset crystallization temperature, and larger rate constant (Zt)1/n. Higher molecular weight resulted in larger cooling function of dynamic crystallization K(T) and lower Ozawa exponent m. For dynamic crystallization, the average value of the Avrami exponent varied from 3.4 to 3.8 and the average value of the Ozawa exponent changed from 2.3 to 2.6 as the number‐average molecular weight changed from 13,000 to 67,000. Morphology studies indicated that both the isothermal crystallization and the dynamic crystallization of PTT from the melt were thermal nucleation processes, and for a fixed temperature between 190°C and 210°C, the nucleation density increased with increasing the molecular weight.
Distributive mixing in a single‐screw extruder—evaluation in the flow direction
Authors: Rwei Syang‐Peng 
Published: April 2004

AbstractThis study investigates distributive mixing in the flow direction for a single‐screw extruder. WIth a custom‐designed transparent extruder, an Image Analysis System, and a newly defined parameter, i.e., distribution index, the distribution mechanism is thoroughly examined with respect to various processing conditions or screw designs. Experimental results indicate that the longitudinal distribution can be enhanced with an increasing RPM, a longer metering section, or a decreasing diameter of the die. However, a plateau region occurs when an optimum condition exists for the RPM and the length of the metering section. In addition, an extruder modified with a barrier, pin‐elements, or high helix angle performs better in the longitudinal mixing than the conventional one. Our results further demonstrate that leakage flow significantly enhances mixing in the flow direction.
The application of an integral type constitutive equation to numerical flow analyses of viscoelastic fluid in unsteady flow
Authors: Shiraishi Yutaka , Narazaki Norio , Kikutani Takeshi 
Published: April 2004

AbstractThe applicability of the Wagner model to numerical flow analyses of the injection molding process is investigated under the following approximations: the strain and stress histories of the molten polymer before the injection is negligible, and the flow field in a mold cavity is treated as Hele‐Shaw flow. A comparison between the results for simple step‐strain‐rate flow calculated with the Wagner model and that calculated with the Leonov model suggests that the Wagner model is superior to the Leonov model for unsteady flow because of its stability and accuracy. Therefore, numerical flow analysis software of a viscoelastic fluid in the injection molding process is developed using the Wagner model. For the analysis, the velocity profile of a Newtonian fluid is used instead of that obtained through iterative calculation. The validity of the developed program is confirmed through a comparison of the results of the computation for two simple flow velocity histories with the analytical results from the Wagner model. Furthermore, the computation time of the developed software is only 1.4 times greater than that of the previous numerical flow analysis of a viscous fluid.
Characterization of anisotropic structure in poly(phenylene vinylene) films
Authors: Ou Runqing , Samuels Robert , Wang Xingwu , Gregory Richard 
Published: April 2004

AbstractThe evolution of the anisotropic structure in poly(phenylene vinylene) (PPV) films was studied using three nondestructive characterization techniques: prism waveguide coupling, infrared dichroism, and X‐ray diffraction. The anisotropic PPV films were thermally converted from precursor drawn films at fixed length. The three‐dimensional refractive indices, infrared dichroic ratios, crystal alignment, and orientation function were determined from each film. The results show that converted cast PPV film has a highly planar structure with a tendency for the PPV chains to orient parallel to the film surface. The a axis of the crystal unit cell is normal to the film plane. One‐way stretching converts the film from a planar structure to a uniaxial structure.
Adhesion enhancement of evaporated copper on HDPE surface modified by plasma polymerization of glycidyl methacrylate
Authors: Zou X. P. , Kang E. T. , Neoh K. G. 
Published: April 2004

AbstractSurface modification of high‐density polyethylene (HDPE) surfaces by plasma polymerization of glycidyl methacrylate (GMA) (the pp‐GMA‐HDPE surfaces), in the absence and presence of Ar plasma pre‐activation of the HDPE substrates, was carried out to enhance the adhesion of the polymer with evaporated copper. THe FTIR and X‐ray photoelectron spectroscopy (XPS) results suggested that the epoxide functional groups on the pp‐GMA‐HDPE surfaces had been preserved to various extents, depending on the RF power used during plasma polymerization. Ar plasma pre‐activation of the HDPE surface led to the strong interaction of the pp‐GMA layer with the HDPE substrate. GMA plasma polymerization at low RF powers and in the presence of Ar plasma pre‐activation was shown to be an effective method for enhancing the adhesion of HDPE with the evaporated Cu. An optimum adhesion strength of about 16 N/cm was achieved between the evaporated Cu and the pp‐GMA‐HDPE surface prepared by plasma polymerization of GMA at 5 W, 100 Pa, 20 sccm for 5 s on the HDPE surface pre‐activated by Ar plasma at 35 W, 100 Pa 20 sccm for 20 s. The adhesion enhancement of the Cu/pp‐GMA‐HDPE assemblies in the presence of Ar plasma pre‐activation of the HDPE substrate was attributed to the covalent bonding of the plasma‐polymerized GMA (pp‐GMA) layer with the HDPE surface, the preservation of the epoxide functional groups in the pp‐GMA layer, and the spatial interactions of pp‐GMA chains with the evaporated Cu matrix.
Epoxy + montmorillonite nanocomposite: Effect of composition on reaction kinetics
Authors: Butzloff Peter , D'Souza Nandika Anne , Golden Teresa D. , Garrett David 
Published: April 2004

AbstractThe objective of this investigation is to determine the effects of montmorillonite layered silicates on the curing kinetics of an epoxy resin. Differential scanning calorimetry was used to probe the changes in reactivity due to the presence of montmorillonite and due to the diamine hardener. The enthalpy of polymerization was strongly affected at compositions greater than 5% (wt) montmorillonite for epoxy + montmorillonite reactions. On introduction of the hardener, epoxy + amine kinetics dominate the reaction for all compositions except for a montmorillonite concentration of 2.5 wt%. X‐ray diffraction was used to determine if the reacted system was exfoliated. The results show a strong montmorillonite composition dependence on the exfoliated state. Transmission electron microscopy of the cured epoxies confirmed a mixed intercalated and exfoliated dispersion at compositions having montmorillonite greater than 2.5 wt%.
The effects of specimen size and testing conditions on fracture toughness evaluation of polypropylene homopolymer
Authors: Santarelli Edgardo , Frontini Patricia 
Published: April 2004

AbstractThe results of an experimental test program performed to investigate the influence of specimen dimensions and testing rate conditions on room temperature fracture toughness of PP homopolymer are presented. The material displayed nonlinear load‐displacement behavior and exhibited small amounts of slow crack growth (ductile tearing) prior to cleavage instability, which invalidates the direct application of the current standards for the determination of KICin polymers. Data points were considerably scattered consistently with typical ductile‐brittle transition patterns. The resulting load‐displacement diagrams were analyzed in terms of KQ, KMAX, and the ratio PMAX/PQ. THe fracture toughness at instability, JC, was also computed and plotted against the amount of stable crack growth in order to construct J‐R curves as a function of size and strain rate. From these curves an alternative critical fracture parameter, KJIC, was calculated. Weibull statistics were used as a tentative approach for treating the scatter of fracture toughness of polypropylene homopolymer in large samples, which exhibited restricted ductile tearing. The significance of each of these methods and the validity and size independence of the corresponding parameters are discussed.
Wall thickness distribution in thermoformed food containers produced by a Benco aseptic packaging machine
Authors: Ayhan Zehra , Zhang Q. Howard 
Published: April 2004

AbstractEffects of process parameters such as forming temperature, forming air pressure and heating time on wall thickness distribution in plug‐assist thermoformed food containers using multilayered material were investigated. Multilayered rollstockbase material formed into containers by thermoforming process using a Benco aseptic packaging machine. Forming temperatures in the range of 131–170°C, airforming pressures of 2, 3, 3. 5 and 4 bars, and heating times of 66, 74, 84, 97 and 114 seconds were used in the thermoforming process. Analysis of wall thickness data obtained for the thermoforming parameters used in this study showed that wall thickness was significantly affected by forming temperature, pressure and heating time at 0.05 significance level. Besides the processing parameters, wall location, container side, and their interactions significantly affected wall thickness. Forming temperature was found to be the principle parameter influencing wall thickness distribution in a plug‐assist thermoforming operation. The optimum operating conditions of the packaging machine for the thermoforming process are: 146–156°C for forming temperature, 2–4 bars for air‐forming pressure and 74–97 seconds for heating time.
Effect of elongational viscosity on axisymmetric entrance flow of polymers
Authors: Gupta Mahesh 
Published: April 2004

AbstractA finite element simulation of the flow in a channel with an abrupt contraction is presented. The effects of the shear and elongational viscosities of a polymer on the entrance flow are analyzed employing a truncated power‐law model. The power‐law index and the strain rate characterizing the transition from Newtonian to power‐law behavior for the elongational viscosity are treated as being independent of the values of these two parameters for the shear viscosity. The effect of flow rate on entrance flow is also analyzed. It is confirmed that the Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow. Extra pressure loss and vortex length predicted by a finite element simulation of entrance loss are compared with the corresponding predictions from Binding's approximate analysis.
Conductive composites of UHMWPE and ceramics based on the segregated network concept
Authors: Bouchet J. , Carrot C. , Guillet J. , Boiteux G. , Seytre G. , Pineri M. 
Published: April 2004

AbstractThe manufacturing of composites of ultra high molecular weight polyethylene and ceramics with conductive properties has been investigated. Attention has been focused on the lowering of the amount of filler necessary to achieve low resistivity. Using segregated networks, mixing large polymer particles and submicron metal or conductive ceramic particles may be an interesting route, provided that the processing method enables to generate the desired structures. Because sintering avoids the intimate blending of the components, it is a suitable technique for this aim. The combined effects of temperature, pressure and sintering time have been investigated. The influence of the blending of the solids on the covering of the polyethylene particles before the sintering has also been pointed out. The typical features related to the concept of a segregated network are discussed in connection with the morphologies of the polymer and ceramic particles. The successful application of the reduction of the percolation threshold by a segregated network in conductive composites of polymer and metallic particles is described.
Dispersity improvement in solvent casting particle/polymer composite
Authors: Schruben Dale L. , Gonzalez Perla 
Published: April 2004

AbstractThe standard solvent casting method for preparing particle/polymer composites is reviewed. Unless extraordinary conditions are used, the standard process is restricted to thin films because of difficulties (blistering) that occur during the solvent removal. These thin films have better dispersion and less clustering of the metal particle loading than if comparable materials were made by adding metal powder into a polymer melt. However, the best dispersion is obtained in a new process where thin films in the standard process go through a redissolving step (or steps) described herein. Characterization by the large particle end of the particle size distribution confirms the reduced clustering tendency of particles in the new process.
Effects of the shape of the energy director on far‐field ultrasonic welding of thermoplastics
Authors: Chuah Yew Khoy , Chien Liang‐Han , Chang B. C. , Liu Shih‐Jung 
Published: April 2004

AbstractAn energy director is widely used in ultrasonic welding to increase the welding speed and quality. In the present work, three different types of energy directors were studied—namely, a triangular, a rectangular, and an innovative semicircular energy director. Experiments were performed using far‐field test samples made of amorphous‐type (ABS) and semicrystalline‐type (PE) thermoplastics. It was found that the weld time is an important parameter of ultrasonic welding for the three types of energy directors studied. Weld pressure has different effects for the types of plastics tested. Increasing the weld pressure will decrease the welding efficiency for ABS. But for PE, increasing the weld pressure to four bars will increase the welding efficiency. The shape of the energy director was found to significantly affect the welding efficiency. In comparison, a semicircular shape was found to yield the highest welding efficiency under the same welding conditions and the triangular shape the lowest. Temperature measurements at the triangular energy director during the welding process indicate that the energy director absorbed 48.5% of the welding energy for ABS and 21.1% for PE. The different energy absorption rates are probably due to the difference in elasticity and viscosity between amorphous (ABS) and semicrystalline (PE) plastics.
Mixing mechanism of three‐tip kneading block in twin screw extruders
Authors: Yoshinaga Makoto , Katsuki Shingo , Miyazaki Masaru , Liu Lijie , Kihara Shin‐Ichi , Funatsu Kazumori 
Published: April 2004

AbstractIn recent years, twin screw extruders have been applied to various kinds of polymer processing. It has been important to find their optimum geometrical configurations and operational processing conditions for the best performance of extrusions and products. Many engineers have been evolving numerical and the experimental methods to characterize the mixing performance for twin screw extruders. We have carried out three‐dimensional flow simulations of kneading blocks in intermeshing co‐rotating twin screw extruders by using the finite element method to quantify their ability in distributive and dispersive mixing. We discuss their performance in distributive mixing for three different type of kneading blocks in terms of the residence time distribution and the nearest distance between markers at various periods of time, by using the marker tracking method. Those numerical techniques and applications of mixing indices have enabled us to quantify and evaluate their abilities in distributive mixing of kneading blocks in twin screw extruders.
Boron nitride as a processing aid for the extrusion of polyolefins and fluoropolymers
Authors: Rosenbaum Eugene E. , Randa Stuart K. , Hatzikiriakos Savvas G. , Stewart Charles W. , Henry Donald L. , Buckmaster Marlin 
Published: April 2004

AbstractThe influence of a new processing additive (fine particles of boron nitride) on the processability of polyolefins and fluoropolymers in extrusion is studied. The equipment used includes an Instron capillary rheometer with two types of dies, namely capillary dies and special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer, and an extruder. Two metallocene polyethylenes and several Teflon® fluoropolymers were tested using these two pieces of equipment. The additive had a significant effect on the extrudate appearance of polyethylene and fluoropolymer particularly in the crosshead dies. It was found to eliminate surface melt fracture and to postpone the critical shear rate for the onset of gross melt fracture to significantly higher values depending on resin type, temperature, and additive concentration (typically 0.005% to 0.5%). To explain the possible mechanism for the effect of the additive on the processability of the resins, rheological measurements using both parallel‐plate and sliding‐plate rheometers were carried out. The rheology of the resins did not seem to change significantly with the addition of boron nitride except for the low‐shear‐rate (low‐frequency) range, where the behavior of the filled resin was found to be similar to that of a crosslinked polymer or a phase‐separated entangled blend. Practical wire coating and tubing extrusion studies for these resins were also carried out.
The brittle‐ductile transition temperature of polycarbonate as a function of test speed
Authors: Gaymans R. J. , Hamberg M. J. J. , Inberg J. P. F. 
Published: April 2004

AbstractThe fracture behavior of polycarbonate was studied as a function of temperature (−80°C to +80°C) and test speed (10−5 to 10 m/s) using an instrumented, singleedged, notched tensile test (SENT). SENT tests give information on the fracture stress, fracture displacements, and fracture energies of polycarbonate, and from these data the average crack speeds were calculated and the brittle‐ductile transitions were determined. The fracture stress and the fracture energies of ductile fracturing samples increased with increasing test speed. The fracture surfaces were studied by scanning electron analysis, and sometimes a mixed mode fracture, part ductile and part brittle, could be seen. At high test speeds, a sharp brittle‐ductile transition was observed, while at low test speeds the transition was more gradual, via a mixed mode region. This mixed mode region decreased in size with increasing test speed and was absent at the higher test speeds. The average crack speeds in the ductile region were directly related to the test speeds. The brittle‐ductile transition temperature increased with the logarithmic of the test speed.
Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent. Part I: Extrusion parameters analysis
Authors: Chalamet Yvan , Taha Mohamed , Vergnes Bruno 
Published: April 2004

AbstractCondensation reaction between a carboxyl terminated polyamide 12 (CTPA) (Mn = 2000 g mol−1) and a dioxazoline [2,2′‐(1,3‐phenylene)‐bis(2‐oxazoline)] (OO) was achieved by reactive extrusion. Extrusion parameters effects on the process were analyzed through residence time distribution (RTD) and conversion distribution (CD) evolutions. RTD was measured using ultraviolet and ultrasonic detectable tracers. RTD measured along the extruder screws showed a decrease of the dimensionless variance (σ) with the reaction progress. Comparing measured molar masses and dispersity with those calculated using CD, competition between condensation and chain scission was detected. Effects of barrel temperature, screw profile, rotation speed and viscous dissipation on the reactive system evolution were analyzed and used for the process optimization. It was shown that a polyester amide with a Dpn 12 can be obtained using this dioxazoline coupling agent by reactive extrusion.
Kinetic parameters estimation for unsaturated polyester‐styrene systems
Authors: Lin Chao‐Ming , Weng Cheng‐I , Ho Cheng‐Ter 
Published: April 2004

AbstractA model modified from the traditional kinetic model is proposed for the determination of the kinetic parameters describing the autocatalytic reaction of polyesterstyrene systems. The proposed method utilizes three experimental data values from the \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{d\alpha }}{{dt}} $\end{document} vs. α curve—the initial value, the peak value, and the maximum value—to solve the kinetic parameters. The curing reaction of a thermosetting polyester was investigated by using the isothermal and dynamic techniques of differential scanning calorimetry (DSC). The results show that the reaction orders m, n and the ultimate conversion are not constant, and instead are functions of temperature. The estimated kinetic curves agree well with the experimental DSC data.
Characterization of UV irradiated space application polymers by spectroscopic ellipsometry
Authors: Bungay Corey L. , Tiwald Thomas E. , Devries Michael J. , Dworak Brad J. , Woollam John A. 
Published: April 2004

AbstractMaterials deployed on long‐duration space missions such as the Hubble Space Telescope (HST) and the proposed International Space Station (ISS) are subject to high ultraviolet (UV) radiation fluences. Some UV radiation present in space has photon energy high enough to dissociate organic polymer molecular bonds. Induced chemical structure modifications can cause changes in optical, structural, and thermal properties. The present work investigates UV radiation effects on DuPont Kapton® H polyimide, polyarylene ether benzimidazole (PAEBI), and DuPont Teflon® fluorinated ethylene‐propylene (FEP). UV irradiated polymers were characterized with in situ and ex situ spectroscopic ellipsometry (SE). Ellipsometric data acquired on UV modified polymers were best modeled as an exponentially graded layer, as opposed to a single layer or linearly graded layer model. Because photon intensity decays exponentially as a function of depth into absorbing materials, an exponentially graded model should be the most physically realistic. Ellipsometric data provided information about changes in UV absorption spectra, depth of damage, and growth trends in the damaged layer.