bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uniform purging of resins in contact bed purge vessels
Authors: Pittenger B. H. , Carson J. W. , Prescott J. K. , Purutyan H. 
Published: April 2004

AbstractResin storage vessels such as bins, silos, and tanks often double as purge vessels, in which products are purged of volatiles or polymerization reactions are controlled. Processing is achieved by gas flowing among resin particles or pellets. Problems associated with these purge vessels include typical bin flow problems such as flow stoppages due to arching or ratholing, erratic discharge, particle segregation, and flooding or flushing. In addition, purging may be non‐uniform or incomplete, and cross contamination between grades may occur. These problems are often the result of either a funnel flow pattern, where some of the material in the vessel moves while the rest remains stationary, or a non‐uniform velocity profile, where some parts of the vessel flow much faster than others. Also, the location and the manner in which gas is injected into the vessel contents affect the uniformity of exposure of polymer particles to the gas. This paper describes methods of designing purge vessels to eliminate stagnant regions. Also, velocity gradients of solids in mass flow vessels (where all of the material is in motion whenever any is withdrawn) are discussed. Considerations of the gas introduction schemes that do not disturb the resin flow patter are also described.
A comparison between experiments and predictions for the blow molding of an industrial part
Authors: Debbaut Benoît , Homerin Olivier , Jivraj Noor 
Published: April 2004

AbstractWe present a numerical simulation for the blow molding of an industrial high density polyethylene part. The rheology of the polymeric material is described by means of an integral viscoelastic fluid model with a multi‐mode relaxation spectrum. A membrane element is applied for performing the blow molding simulation of geometrically complex objects such as a bottle with a handle; the motion governing equations are described by means of a Lagrangian representation. The contact between the parison and the moving mold is handled by means of a robust algorithm. The numerical tool is applied for the production of a bottle with a handle. The predicted results are compared with their experimental counterparts. In particular, we focus on the thickness distribution of the blow product.
Effect of viscosity variation with temperature on the compounding behavior of immiscible blends
Authors: Ratnagiri Ram , Scott Chris E. 
Published: April 2004

AbstractMorphology development in the compounding of immiscible blends depends on a number of material properties and process conditions. In this work, different model blend systems are considered to outline the effects of the relative transition temperatures and viscosities of the blend components. We focus on the evolution of blend morphology, specifically phase continuity. A framework based on these factors is presented for analyzing the compounding behavior of immiscible blend systems. With the minor component at 10 wt%, it was found that phase inversion during compounding occurred in blends with a viscosity ratio of less than 0.2, independent of the relative transition temperatures. It was shown that in these constant mixer temperature runs, the torque trace was not a completely reliable indicator of phase inversion. When a temperature ramping program was used, the lower melting point component formed the continuous phase initially, independent of the viscosity ratio. Quantitative measures of the amount of minor component which was continuous at different mixing times were made using selective extraction in a Soxhlet apparatus. Results from compounding runs of polycarbonate/ polyethylene, an amorphous copolyester/polyethylene and polybutylene/polycaprolactone blends are presented.
Phase separation influence on the performance of CTBN‐toughened epoxy adhesives
Authors: Klug Jeremy H. , Seferis James C. 
Published: April 2004

AbstractEpoxy adhesive systems were formulated and tested for their bonding behavior. Fumed silica and elastomer type and concentration were varied for the purpose of investigating their influences on intermediate and final adhesive performance properties. Of special interest was analyzing the role that flexibilized elastomer, that which does not phase separate during cure, played in these properties. Adhesive systems were tested with a commercial prepreg system using both bonded and cocured geometries. Dynamic mechanical analysis and optical microscopy showed the phase separation of the rubber was significantly influenced by the silica addition. Elastomer‐rich dispersed phase growth rates were depressed resulting in a lower percentage of toughening domains. Mode I and II fracture energies were a strong function of dispersed phase particle size, flexibilized elastomer type/content, and residual stress considerations at the resin‐resin interface. There were distinct differences between bonded and cocured fracture results with bonded samples generally outperforming cocured specimens due to changes in the surface roughness, resin flow properties, and interfacial stress build‐up. Collectively, this work illustrates the importance of phase separation behavior on the final part morphology and performance for liquid elastomer toughened epoxy adhesives.
Residual stress development in a bi‐layer coating
Authors: Yan Gu , White J. R. 
Published: April 2004

AbstractMeasurements have been made of the residual stress development in a solventdeposited thermoplastic coating and a two‐component thermoset by monitoring the bending of the steel substrate using strain gauges. The stresses in single layers were found to be significant when compared to the strength of the coatings. When the thermoset was applied on top of the thermoplastic (undercoat), the stress in the top coat was much less than that obtained when the thermoset was applied directly to the steel substrate. This was deduced using a new elastic analysis for tri‐layers (substrate plus bi‐layered coating).
Residual stresses in marine coatings under simulated service conditions
Authors: Yan Gu , White J. R. 
Published: April 2004

AbstractStudies have been made of the effect of cyclic temperature changes and wet/dry cycling on the residual stresses in marine coatings applied to steel substrates. A thermoplastic and a thermoset have been use as single coatings and as bi‐layers consisting of the thermoset applied on top of the thermoplastic. Cyclic changes associated with differential thermal expansion/contraction between substrate and coating and with water absorption or desorption were observed, and it was found in addition that progressive changes in residual stress were sometimes superimposed on the cyclic changes. The effect was larger with the thermoplastic coating than with the thermoset. The stresses developed in the bi‐layers were generally smaller than those in single layer coatings and were generally less sensitive to the cyclic changes in conditions. The effects were partly controlled by the thicknesses of the two layers in the bi‐layer coatings. Stresses as high as 6 MPa were measured during the course of this work, a significant fraction of the failure strength of the coatings.
Processing of short fiber reinforced polypropylene. II: Statistical study of the effects of processing conditions on the impact strength
Authors: Barbosa Silvia E. , Kenny José M. 
Published: April 2004

AbstractWithin the general objective of analyzing and modeling the processability of polypropylene and of its short fiber composites, a statistical analysis of the relationship between processing conditions and final properties has been performed applying modern experimental design concepts. In order to gather the largest amount of information with a manageable quantity of experiments, Taguchi methods were used for the design of injection molding tests and for the analysis of experimental fiber orientation and impact strength results. Two levels of each variable of interest were selected, and the results of the analysis not only show which of the processing variables are predominant but also show that interactions between variables must be taken into account. The approach presented here offers a viable route to the scaling‐up of the injection molding process through the reduction of the number of variables in the prediction of the processing behavior of semicrystalline polymers and of their composites.
Kinetic study and simulation of the precopolytransesterification step in the copoly(ethylene‐polyoxyethylene terephthalate) production process
Authors: Cruz‐Guerra Cornelio De La , García‐De La Mora Gustavo A. , Cruz‐Gómez M. Javier 
Published: April 2004

AbstractThe kinetics of the precopolytransesterification step for the production process of the copoly(ethylene‐polyoxyethylene terephthalate), COPEPOET, has been analyzed. The prepolytransesterification step involves two competitive parallel reactions generating the same by‐product, ethylene glycol: 1. Prehomopolytransesterification reaction of bis (2‐hydroxyethylene terephthalate), BHET, with itself and 2. Precopolytransesterification reaction of BHET with poly(oxyethylene), POE. The kinetic constants of both reactions, BHET with BHET and BHET with POE, were calculated. The analysis was made as follows: 1. A kinetic model was developed in order to calculate the kinetic constants kH and kC of the prehomopolytransesterification and precopolytransesterification reactions; 2. The simulation of the precopolytransesterification step was carried out by integrating the differential equations, which describe the prepolytransesterification step. A fourth‐order Runge‐Kutta method was used for this integration. Several values that fall within the interval of 0.05 to 1.5 were assigned to the rate constant ratio kH/kC value, a set of kH/kC value, a set of kH and kC values were obtained. The parameters of the Arrhenius equation A and E were evaluated by means of a multiple regression analytical method; and 3. By comparison between theoretical and experimental data the best kH/kC value was obtained. The kH value was found to be several times smaller than that of kC.
Numerical modeling of injection/compression molding for center‐gated disk: Part I. Injection molding with viscoelastic compressible fluid model
Authors: Kim I. H. , Park S. J. , Chung S. T. , Kwon T. H. 
Published: April 2004

AbstractThe present study attempted to numerically simulate the process in detail by developing an appropriate physical modeling and the corresponding numerical analysis for injection molding and injection/compression molding processes of centergated disks. In Part I, a physical modeling and associated numerical analysis of injection molding with a compressible viscoelastic fluid model are presented. In the distribution of birefringence, the packing procedure results in the inner peaks in addition to the outer peaks near the mold surface, and values of the inner peaks increase with the packing time. Also, values of the density in the core region increase with the packing time. From the numerical results, we also found that birefringence becomes smaller as the melt temperature gets higher and that it is insignificantly affected by the flow rate and the mold temperature. As far as the density distribution is concerned, mold temperature affects the distribution of density especially near the wall. But it was not significantly affected by flow rate and melt temperature. Numerical results of birefringence coincided with experimental data qualitatively, but not quantitatively.
Numerical simulations of annular extrudate swell using various types of viscoelastic models
Authors: Otsuki Yasuhiko , Kajiwara Toshihisa , Funatsu Kazumori 
Published: April 2004

AbstractIn this study, numerical simulations of annular extrudate swell of high density polyethylene (HDPE) were carried out. Some important viscoelastic models, such as the Larson, the PTT and the K‐BKZ model, were employed for the swell calculation through various types of dies. These numerical results were compared with the experimental ones. The numerical results of the swell behaviors were very different in each viscoelastic model, while their simple shear flow characteristics were almost the same. As a result, the uniaxial elongational viscosity for large deformation as the steady state region is not important, but the property for relatively small deformation has remarkable effects on the numerical results for the die that have a uniaxial contraction region. Both reversible and irreversible types were tried for the Larson model. It was found that there was a difference between the irreversibility assumption of the K‐BKZ model and the Larson model. While there was a serious difference in the response for reversing strain among these viscoelastic models, the response was very important to predict annular extudate swell behavior.
An experimental technique for the characterization of molecular orientation through the thickness of plastic products
Authors: Daly H. Ben , Cole K. C. , Sanschagrin B. , Nguyen K. T. 
Published: April 2004

AbstractAn experimental technique has been developed for the characterization of the molecular orientation through the thickness of plastic products. The technique consists of milling the specimen to the depth where the molecular orientation is to be measured, polishing the exposed surface, and characterizing the polished surface by external reflection infrared spectroscopy. The technique was first tested on both unoriented and oriented poly(ethylene terephthalate). It was found that the intermediate steps of the process change the apparent surface orientation, but carrying the process to completion (to a finish of 0.05 μm) removes the altered material and leaves a surface whose orientation corresponds to that of the original sample. The technique was also tested on polyetheretherketone (PEEK), high density polyethylene (HDPE), and liquid crystal polymer (LCP). For polymers with a high transition temperature, like PEEK and LCP, the conclusions are the same as for PET. However, for polymers like HDPE, with a low glass transition temperature, the milling and polishing process used to prepare the samples can alter the orientation to a greater extent. This effect can be reduced by cooling the sample with liquid nitrogen during preparation.
Effect of natural zeolite on the mechanical properties of epoxy matrix
Authors: Lee Jae‐Young , Shim Mi‐Ja , Kim Sang‐Wook 
Published: April 2004

AbstractThe mechanical properties of epoxy systems filled with natural zeolite were studied. To study the effect of the filler content and particle size, natural zeolites of three different particle sizes were added to epoxy resin at various contents. The effect of strain rate on the tensile strength was also tested. With increasing zeolite content, Tg and Young's modulus increased; however, tensile strength and impact strength decreased. As the zeolite particle size decreased, all these properties increased, and tensile strength increased, with increasing strain rate. The fracture surface of the composite showed more complex morphology with increasing zeolite content.
Mechanical properties of PVC/SBR blends compatibilized by acrylonitrile‐butadiene rubber and covulcanization
Authors: Zhu S.‐H. , Chan C.‐M. , Wong S. C. , Mai Y.‐W. 
Published: April 2004

AbstractThe mechanical properties of poly(vinyl chloride) (PVC)/styrene‐butadiene rubber (SBR) blends compatibilized by acrylonitrile‐butadiene rubber (NBR) were studied. A sulfur curing system was employed to crosslink the rubber of the blends. In the case of the blends without any curing agents, an increase in NBR content did not improve the tensile strength and elongation‐at‐break. However, a significant improvement in the mechanical properties was observed when NBR was added as a compatibilizer and the blend was vulcanized. In the PVC/NBR/SBR (50/10/40) blends, the tensile strength and elongation‐at‐break increased with an increase in sulfur concentration. This improvement was attributed to covulcanization between NBR and SBR. The fracture toughness of PVC/NBR/SBR (50/10/40) blends was characterized by the critical strain energy release rate, Gc. In the case of the PVC/NBR‐29/SBR (50/10/40) blends, an increase in sulfur concentration resulted in a dramatic increase in Gc. However, the Gc value of PVC/NBR‐40/SBR (50/10/40) blends decreased with an increase in sulfur concentration owing to the brittle behavior of one of the blend components—the PVC/NBR‐40 (50/10) phase.
Comparison of residual stress predictions and measurements using excimer laser layer removal
Authors: Jansen K. M. B. , Orij J. J. W. , Meijer C. Z. , Dijk D. J. Van 
Published: April 2004

AbstractResidual stresses in injection molded polymer parts can have a major effect on product performance and are therefore often undesirable. Two different models for residual stress formation in injection molded products exist in the literature. The first model assumes that stresses in molded parts are identical with free quench stresses. Deviations are attributed to molecular orientation effects. The second model assumes that no slip occurs and that stresses are related to the holding pressure. Careful measurements should be able to differentiate between these models. In this study the layer removal stress measurement technique was improved by using an excimer laser for the milling operation. In that way stress relaxation during measurements was avoided and thin layers of uniform thickness could be removed. Both resolution and measurement accuracy were greatly improved. Stress distributions in polycarbonate plates molded under low holding pressures turned out to be of the free quenching type, whereas those molded under higher pressures were of the pressure type. All stress distributions could be predicted by a recent theory that comprises the two models as limiting cases.
Cycle‐to‐cycle and within‐cycle adaptive control of nozzle pressure during packing‐holding for thermoplastic injection molding
Authors: Yang Yi , Gao Furong 
Published: April 2004

AbstractProper control of packing is critical to the quality of injection molded parts. To control the packing phase, nozzle pressure was chosen as a better indicator of the degree of packing than cavity pressure. This allows one nozzle pressure transducer to be used for different molds and is more suitable for industrial applications. The dynamics of nozzle pressure during the packing stage were studied and found to be both nonlinear and time varying. Therefore, an adaptive self‐tuning controller was designed and implemented. Several improvements—an anti‐windup estimate, an adaptive feedforward, and cycle‐to‐cycle adaptation—were incorporated to produce excellent packing pressure control results. The controller works well for a wide range of different conditions, such as set point profiles, barrel temperatures, molds, and materials.
The cocrystallization behavior of binary blends of isotactic polypropylene and propylene‐ethylene random copolymers
Authors: Kim Man‐Ho , Alamo Rufina G. , Lin J. S. 
Published: April 2004

AbstractRapidly crystallized blends of metallocene isotactic polypropylene and propylene‐ethylene random copolymers with an ethylene content varying from 0.76 to 7 mol% were found to cocrystallize to different degrees depending on the composition of the comonomer and content of copolymer in the blend. The degree of molecular mixing was studied using differential scanning calorimetry and solvent extraction techniques. A high extent of cocrystallization is obtained in the whole composition range of blends with a copolymer having up to ∼ 2 mol% of ethylene. The degree of cocrystallization decreases gradually with increasing ethylene content or with increasing copolymer content in the blend. It is found that for ethylene contents as high as 5–7 mol% the copolymer rich blends show partial separate crystallization of the propylene ethylene copolymer. Thus, these crystals were selectively extracted at temperatures just above the dissolution temperature of the pure copolymer. In these blends, the fractional content of segments from the copolymer molecules incorporated in the cocrystal is low, yet it prevents extraction of these molecules at temperatures above the dissolution temperature of the copolymer. The degree of cocrystallization is explained by differences in crystallization kinetics of the pure components. The percentage of extracted material was found to be directly related to the dissolution temperature of the cocrystal which was also found to be a linear function of the inverse of the crystallite thickness. The high extent of cocrystallization observed for these polypropylene blends contrasts with comparable blends of polyethylenes. The blends of linear PE with a copolymer of 4 mol% branch units and higher, form separate crystals even after rapid crystallization.
Crystallization behavior and rheological properties of polycarbonate and polypropylene blends
Authors: Chun Yong Sung , Jung Hyun Chul , Han Min Soo , Kim Woo Nyon 
Published: April 2004

AbstractCrystallization behavior and rheological properties of blends of bisphenol‐A polycarbonate (PC) and polypropylene (PP) prepared by screw extrusion have been investigated by differential scanning calorimetry (DSC), polarized‐light microscopy, scanning electron microscopy, and a Rheometrics Mechanical Spectrometer. In the study of thermal analysis of PC‐PP blends by DSC, double crystallization peaks were observed in the PC‐rich compositions. In the study of spherulite of 7/3 PC‐PP blend, large droplets (>25 μm) of PP were crystallized between 115°C and 105°C, and then small droplets (<10 μm) of PP were crystallized at about 90°C. This result is consistent with the double crystallization behavior such that heterogeneous and homogeneous nucleations have been observed at about 105°C and about 85°C, respectively, by DSC measurements. From the results of rheological properties of the PC‐PP blends, the storage modulus of the PC‐PP blends at low frequencies has larger value than that of the simple mixing rule. The elasticity increase from the simple mixing rule is consistent with the emulsion model for a dispersed system.
Orientation of LCP blown film with rotating dies
Authors: Lusignea Richard W. 
Published: April 2004

AbstractLiquid crystal polymers (LCPs) have been commercially available for over 10 years, but their use has been limited almost entirely to injection molded parts, totaling only about 7.5 million kg per year. Much larger volume uses of LCP in film, tube, pipe and extruded parts have not been exploited because of uncontrolled orientation in LCP. This paper explains how shear and elongation forces, controlled by rotating extrusion dies, orient LCP film, tube and other extruded parts. Applications to electronic, medical and high barrier packaging markets are discussed.
Characterization of the orientation in synthetic polymer sheets using far‐infrared radiation
Authors: Drouin Bernard , Gagnon Richard 
Published: April 2004

AbstractMolecular orientation and mass distribution have been measured in various synthetic polymers using a characterization technique developed by the authors. This method is based on the transmission of polarized far‐infrared radiation. Fairly thick samples (polyethylene up to one centimeter thick) can be tested easily with this nondestructive approach. Spatial resolution in the millimeter range is possible. This allows the characterization of various industrial products made of nylon, polyethylene, polypropylene or polyesters, such as liquid containers, injection‐molded parts, thick extruded or drawn sheets and rods, etc. Potential scientific and industrial applications are discussed.