bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinematics and deformation characteristics as a mixing measure in the screw extrusion process
Authors: Kwon T. H. , Joo J. W. , Kim S. J. 
Published: May 2005

AbstractThe present paper proposes “Deformation Characteristics” (DC) as a new deformation measure of screw extrusion processes, based on the Green deformation tensor. In contrast to previous strain measures heuristically proposed by Mohr, et al., Mckelvey, and Pinto and Tadmor, the new DC can naturally incorporate the demixing phenomena and systematically take into account the three‐dimensional circulatory flow with the screw flight effect. Therefore, DC can be regarded as an improved strain measure. “Weighted Average Deformation characteristics” (WADC) is also proposed to indicate the overall deformation characteristics as a quantitative measure to the “goodness of mixing” of the extrusion process. The present paper includes discussion on delicate differences between DC and several other strain measures in case of the two‐dimensional velocity approximation, and on the application of DC into a general three‐dimensional velocity field obtained by a quasi‐three‐dimensional finite element analysis of extrusion processes. In determining WADC in the three‐dimensional application, the residence time distribution function, including the three‐dimensional circulatory flow effect, is used.
The rheological characterization of fluorinated thermoplastics using squeezing flow viscometry
Authors: Deng Yong , Martin George C. , Kohut Gerard P. , Gotro Jeffrey T. 
Published: May 2005

AbstractA squeezing flow viscometer was developed to characterize the rheological properties of luorinated thermoplastics. The viscosities of CTFE (polychlorotrifluorethylene) and FEP (a copolymer of tetrafluoroethylene and hexafluoropropylene) were determined using the viscometer by assuming that the shear‐rate dependent viscosity can be described by a power‐law, a truncated power‐law, or an Ellis model. The results were in agreement with the viscosities measured with steady shear cone‐and‐plate viscometry and oscillatory cone‐and‐plate rheometry. Although the squeezing flow behavior of the polymers can be well explained by the purely viscous models, the power‐law model is valid only for a limited range of shear‐rates whereas the other two models are useful over a relatively wide range.
Influence of a compatibilizing agent on the phase morphology of a polyethylene‐polyamide 6 blend in a modular intermeshing co‐rotating twin screw extruder
Authors: Lim Soonho , White James L. 
Published: May 2005

AbstractA study of the influence of a compatibilizing agent on phase morphology development in a 75/25 polyethylene/polyamide‐6 blend in a modular co‐rotating twin screw extruder is presented. The development of phase morphology along the axis of the modular screw was observed by cooling the extruder and removing the polymer from the screw channels. Changes in phase morphology due to the addition of a compatibilizer have been investigated using scanning electron microscopy. Sufficient quantities of compatibilizing agent produce significant increases in the rate of mixing and also reduce the scale of the phase morphology. Much larger quantities (5%) than actually required for interface coverage are needed for rapid mixing. This seems to be due to the high viscosity of the matrix.
Does quantum magic impinge on polymer physics?
Authors: Hearle John W. S. 
Published: May 2005

AbstractPenrose states that quantum effects can occur even in relatively large systems when energy differences remain small. This is just the situation with polymer materials. A quantum description by Penrose of the formation of quasi‐crystals can be rewritten to apply to polymer crystallization. The implications of the need to take account of quantum effects are discussed. Another approach based on the quantization of energy levels in clusters of atoms offers a possible explanation of heat setting in nylon and polyester fibers. Finally some problems of the interpretation of quantum theory are discussed.
Characterization of the interfacial bond in paper‐polypropylene‐paper laminates
Authors: Johnston Stephen A. , Somodi Paul J. , Eby R. K. , Bernstein Bruce S. 
Published: May 2005

AbstractThe interfacial strength of two paper‐polypropylene‐paper laminates used for electrical power transmission cable insulation has been measured using a peel test after a variety of conditionings that simulate the service thermal stress conditions. Immersion in dielectric oil at 23°C causes little decrease in peel strength, but heating in the oil at 90°C causes a rapid initial loss followed by a slow loss of strength. Cyclic and static heating show that cyclic fatigue is not a factor as the initial loss of strength occurs in a time comparable to the first two test cycles and further heating causes much less loss of strength. Tensile and compressive stresses resulting from cable winding have no effect on the loss of bond strength during heating in oil. Vacuum drying of the laminate and oil (as in cable manufacture) before heating results in less decrease in peel strength than heating without prior drying. Optical and electron microscopy show minimal wetting of the paper fibrils by the polypropylene with only a few having been either normal to or at a steep angle to the polypropylene surface. That is, the fibrils appear to be parallel to the interface and only partially immersed in the polypropylene. Micrographs show little, if any, differences between the interfaces on the two sides as well as little paper on the polypropylene after delamination and vice versa. It is suggested that the bonding mechanism is a combination of weak mechanical interlocking and secondary bonds. It is also suggested that swelling of the polypropylene relative to the paper by the dielectric oil at 90°C weakens the interfacial bond.
Thermoplastic polyheterocycles. II: Polyalkylene‐imides
Authors: Preston J. , Tropsha Y. 
Published: May 2005

AbstractPolyalkylene‐imides (i.e., aliphatic‐aromatic polyimides) were prepared smoothly in N‐methyl pyrollidone from straight chain aliphatic diamines and pyrromellitic dianhydride. Melting points of the polymers ranged from about 300 to 450°C, depending of the length of the alkylene chains. An odd/even effect related to the alkylene chain was noted for melting points and glass transition temperatures (Tg) of the polymers. The Tgs were relatively high, especially when compared to similarly structured polyalkylene‐heterocycles, e.g., polyakylenebenzoxazoles.
Deformation and entanglement in semicrystalline polymers
Authors: Plummer C. J. G. , Cudré‐Mauroux N. , Kausch H.‐H. 
Published: May 2005

AbstractTransmission electron microscopy and optical studies of thin films of isotactic polystyrene (iPS) and polyoxymethylene (POM) provide evidence for a distinction between crazing mechanisms in semicrystalline polymers above and below Tg. In the latter temperature regime, deformation in iPS and POM crystallized at high supercooling has been discussed in terms of existing models for crazing in amorphous glassy polymers, based on entanglement ideas. Above Tg, where the difference in mechanical behavior of the amorphous and crystalline regions becomes marked, the fibrillar nature of local deformation appears to be a consequence of the inhomogeneity of the undeformed polymer.
Dynamic mechanical analysis and its relationship to impact transitions
Authors: Woo Lecon , Westphal Stanley , Ling Michael T. K. 
Published: May 2005

AbstractDetailed, instrumented impact tests were carried out between about − 100 and 60°C for flexible poly(vinyl chloride) (PVC), ethylene vinyl acetate (EVA), and polypropylene (PP) films. Secondary impact transitions in addition to the main transitions were detected for all three films, indicating that multiple impact transitions may be far more general in occurrence than commonly expected. Wide frequency (from 0.05 to 100 Hz) dynamic mechanical spectra of the same materials were also generated over similar temperature ranges. A new data treatment method was proposed whereby the material dissipation function was evaluated by summing the responses over broad frequency ranges of the loss modulus and the impulse spectrum. The dissipation function when plotted as a function of temperature was found to accurately (to within 3 to 5°C) predict the location of the main impact transitions for all three polymers. In addition, the existence and location of the secondary impact transitions for both PVC an PP were predicted. Both the functional form and the temperature match between the experiments and predictions strongly support the validity of the proposed method. However, some discrepancy remained in predicting the very low temperature (−65°C) impact transition for EVA.
Blends of a thermotropic LCP and a thermoplastic elastomer. II: Formation and stability of LCP fibers
Authors: Verhoogt H. , Willems C. R. J. , Van Dam J. , De Boer A. Posthuma 
Published: May 2005

AbstractThe formation of fibers during blending of a thermotropic liquid crystalline polymer (LCP) with a thermoplastic elastomer (TPE) using shear flow, and the stability of the fibers and the blend morphologies at elevated temperatures were studied. The polymers used were Vectra A900 (LCP) and Kraton G1650 (TPE). Fiber formation in (predominantly) shear flow was studied using a single screw extruder of which the die was removed. Fibers were obtained in blends with 5 vol% LCP at shear rates as low as 6.3 s−1. Conventional extrusion through a die was used for preparing materials for the studies of the thermal stability of blends and isolated fibers–isolated LCP‐fibers surrounded by a TPE‐matrix disintegrate when held above the melting point of the LCP. Annealing of the blends at this melting temperature results in changes of the morphology and in a fairly rapid decrease of the modulus of elasticity.
Controller design and performance analysis for a reactive extrusion process
Authors: Pabedinskas A. , Cluett W. R. 
Published: May 2005

AbstractThis paper presents the design and analysis of a process control strategy for a reactive extrusion polypropylene degradation process. The primary control objective is to continuously produce polypropylene with desired properties (viscosity) despite variations in the properties of the feed material. The viscosity of the polypropylene, measured using an In‐line Wedge Rheometer, is controlled by manipulating the feed concentration of the peroxide which acts as the initiator for the degradation reaction. An empirical model of the reactive degradation process is developed which describes the process dynamics and the characteristic process disturbances. Minimum variance (MV), constrained minimum variance (CMV), and pole placement (PP) controllers are first evaluated and compared in simulation. Then, a pole placement controller is implemented on the actual reactive extrusion process, with results being presented for the response of the controlled process to load disturbances due to feed material changes.
Comparative study of warpage, global shrinkage, residual stresses, and mechanical behavior of rotationally molded parts produced from different polymers
Authors: Bawiskar Santosh , White James L. 
Published: May 2005

AbstractA comparative study of warpage, global shrinkage, and residual quench stresses developed in rotational molding is made for a series of thermoplastics including various polythylenes, polypropylene, polyamide‐6, polycarbonate, and polystyrene. The influence of rate of quench on uniaxial stress strain and impact behavior of rotomolded parts was also studied. Generally, warpage, global shrinkage, and residual stresses increase with increasing quench rate for all the polymers. Further, the levels of warpage and global shrinkage increases with extent of crystallization, i.e., products from glassy polymers exhibit little warpage and those from highly crystalline polymers are highly warped. Increasing rate of quench tends to increase elongation to break and impact strength.
Masked edge effects when measuring diffusion coefficients with the cup method
Authors: Claesson J. , Hagentoft C.‐E. , Wadsö L. 
Published: May 2005

AbstractWhen diffusion coefficients are measured with the cup method, the exposed area is often less than the area of the sample. Because of this masking effect the measured diffusion coefficient is overestimated. The present article presents simple formulas based on two‐dimensional analytical solutions to correct for this in cylindrical cup samples. Different cases of anisotropical diffusion are dealt with. The error in the analytical solutions is determined by numerical computer simulations.
Three‐dimensional finite element analysis of polymeric fluid flow in an extrusion die. Part I: Entrance effect
Authors: Wen Shu‐Heng , Liu Ta‐Jo , Tsou Jenq‐Der 
Published: May 2005

AbstractThe Galerkin finite element method has been applied to study the three‐dimensional flow field of power‐law fluids inside an extrusion die. Two inlet designs, i.e., center‐fed and end‐fed, have been considered. The effects of inertial force as represented by the Reynolds number Re, inlet geometry, and the power‐law index n on lateral flow uniformity and vortex formation in the entrance region have been examined. A flow visualization technique has been carried out to experimentally verify the theoretical prediction of the three‐dimensional flow field inside a die. It has been found that increasing Re or decreasing n will deteriorate flow uniformity. Depending on the direction of the inlet jet stream, the inertial force may create a flow peak in the central region of a center‐fed die, or the maximum flow rate will appear close to the end of the die for an end‐fed die. For highly shear‐thinning fluids, lower flow rates are always observed close to the end of the dies. It is concluded that creating a plug flow in the inlet tube of the extrusion die is advantageous for both center‐fed and end‐fed designs.
Continuous crosslinking of ethylene vinyl acetate and ethylene methyl acrylate copolymer blends by on‐line microwave heating
Authors: Cassagnau P. , Michel A. 
Published: May 2005

AbstractThe transesterification reaction catalyzed by dibutyltin oxide has been used to crosslink miscible blends (at about 200°C) of ethylene vinyl acetate (EVA) and ethylene methyl acrylate (EMA) copolymers. Then, microwave heating at 2.45 GHz with the fundamental TE01 mode was used for activation of this crosslinking reaction. The microwave treatment was carried out in a continuous process through a resonant cavity on line with a twin screw extruder equipped with a strip die or a circular die, which imposed the shape of the samples in the waveguide. Therefore, a shape factor due to the geometry of the samples and their orientation with respect to the electromagnetic field was defined. Last, this technique was applied to the microwave crosslinking of an EVA/EMA blend dispersed in a polypropylene matrix and consequently offers a new route to control the morphology of the polymer blends.
Prediction of stationary interfaces in coextrusion flows
Authors: Agassant J. F. , Fortin A. , Demay Y. 
Published: May 2005

AbstractA computation method for the development of the interface in coextrusion flows is proposed. It is based on the transformation of the nonmixing condition at the interface into a transport equation of the rheological constants in the whole domain. The coextrusion flow of a Newtonian fluid and of a Carreau fluid is tested. It is pointed out that the interface location is strongly dependent on the flow rate and on the flow rate ratio.
Melt crystallization kinetics of syndiotactic polystryrene
Authors: Wesson R. D. 
Published: May 2005

AbstractThe crystallization kinetics of syndiotactic polystyrene (SPS) were studied using nonisothermal DSC analysis. Crystallization rates and half‐times were determined from the glass transition temperature (∼ 100°C) up to the melt temperature (∼ 270°C) for various molecular weight SPS polymers. The results suggest that the crystallization rate of SPS is molecular weight dependent. These results are also compared with previously determined crystallization kinetics of high density polyethylene. The maximum crystallization rate of high density polyethylene is approximately ten times greater than that of SPS.
Processing effects on poly(ethylene terephthalate) from bottle scraps
Authors: Giannotta Giorgio , Po' Riccardo , Cardi Nicoletta , Tampellini Elena , Occhiello Ernesto , Garbassi Fabio , Nicolais Luigi 
Published: May 2005

AbstractProcessing of virgin and recycled poly(ethylene terephthalate) (PET) in a twin screw extruder evidences the degradative effect caused by thermal decomposition of poly(vinyl chloride) (PVC) and other impurities, e.g. adhesives, at the processing temperature. Lower melt viscosity and molecular weight, along with higher carboxylic end group concentration, were observed for recycled PET, the extent depending on PET purity. In an attempt to investigate the correlation between the kinetics of degradation phenomena and the level of thermomechanical stress, a novel dynamic method of evaluating thermal stability in processing conditions was developed. Such a method allows the achievement of long equivalent residence times while using lab‐scale extruders. As a result of these experiments, PVC‐rich recycled PET was shown to reach very low melt viscosity after less than 10 min in processing conditions, while virgin PET retained high viscosity even after 30 min.
Flow field analysis of a cavity transfer mixer
Authors: Wang Chicheng , Manas‐Zloczower Ica 
Published: May 2005

AbstractThe cavity transfer mixer (CTM) was primarily designed as a distributive mixing device to be used as an add‐on unit to existing extruders. In determining the CTM overall mixing efficiency as well as its potential use for various applications, the flow patterns/characteristics within this mixer must be well understood. In this work, a fluid dynamics analysis package, FIDAP, based on the finite element method was employed to simulate the flow patterns in a CTM with 6 rows and 4 cavities per row. A 3D, isothermal flow analysis was carried out and the fluid of choice was a flexible polyvinylchloride whose rheological behavior is described by a power‐law model fluid. The flow field was characterized in terms of velocity profiles, pressure distributions, shear rates/shear stresses generated and a parameter λ quantifying the elongational flow components. The results of the flow simulations were compared with experimental data. The CTM potential use for dispersive mixing was discussed.
Parameter estimation for analysis of vapor diffusion in polymers
Authors: Hsu W. P. , Lo P. Y. , Kwei T. K. , Myerson A. S. 
Published: May 2005

AbstractThis paper presents a general method for estimation of diffusion coefficient and other relevant parameters for the analysis of vapor diffusion in polymers. Sorption curves generated by the constants estimated using the parameter estimation method presented here are in closer agreement with experimental curves than curves generated by other conventional methods.
Coupling agent and glass fibers in polyester mortar
Authors: Mebarkia S. , Vipulanandan C. 
Published: May 2005

AbstractThis study investigates the influence of aggregates, glass fibers and a coupling agent on the compressive and flexural (three‐point and four‐point bending) behavior of a polyester mortar. Particle size of fine aggregates (quartz and limestone) varied from 0.1 to 5 mm (0.004 to 0.2 inch) and the glass fiber content was varied up to 6% by weight of mortar. A silane was introduced into the polyester mortar by pretreating the aggregates and the glass fibers. The mechanical properties of mortar were studied at room temperature. The test results indicate that the selection of aggregate type, size and distribution is very important. Silane treated aggregate systems showed more than 66% increase in compressive strength and 35% increase in flexural strength when compared to the untreated systems. Addition of glass fibers enhances the strength and toughness of the polyester mortar, and silane treatment of glass fibers helps to further enhance these properties. Flexural (three‐point bending)‐to‐compressive strength ratio varied from 0.28 to 0.35 for unreinforced system and from 0.26 to 0.54 for the reinforced system. The mortar with only 14% polyester and 86% aggregates (by weight) and a coupling agent had a compressive strength of 103 MPa (15,000 psi) which is 94% of the polyester polymer strength. A stress‐strain relationship is proposed to represent the complete stress‐strain response under compression and flexural loading. Also, a method is proposed to quantify the failure patterns.
Curing of acrylated epoxy resin based on bisphenol‐S
Authors: Liaw Der‐Jang , Shen Wen‐Chang 
Published: May 2005

AbstractThe acrylated diglycidyl ether of bisphenol‐S was prepared by reacting diglycidyl ether of bisphenol‐S (DGEBS) with acrylic acid using dimethyl benzylamine as a catalyst. The acrylated epoxy resin thus obtained was characterized by IR, 13C‐NMR, and DSC. The curing reaction of the acrylated epoxy resin with dicumyl peroxide was investigated by differential scanning calorimetry at three different heating rates. The overall curing kinetics were found to be approximately second order, independent of the scan rate. The TGA was used to investigate the thermal decomposition of acrylated epoxy resin and to determine the kinetic parameters such as activation energy, preexponential factor, and reaction order. Such information can be used for quick estimation of polymer lifetimes.
Thermal and mechanical properties of injection molded blends of a liquid crystalline polymer and poly(butylene terephthalate)
Authors: Engberg K. , Ekblad M. , Werner P.‐E. , Gedde U. W. 
Published: May 2005

AbstractThe microstructure and the thermal and mechanical properties of injection molded samples of different blends of Vectra (LCP) and poly(butylene terephthalate) (PBT) have been studied. Differential scanning calorimetry and hot‐stage polarized light microscopy showed that the crystallization of PBT was unaffected by the presence of LCP. X‐ray diffraction showed that the PBT component was always unoriented in the injection molded samples. Blends with less than 28 vol% LCP exhibited the same stiffness and the same coefficient of linear thermal expansion as PBT. Blends containing more than 38 vol% LCP contained an oriented LCP phase and had a stiffness in accordance with the upper‐bound composite equation. The coefficients of linear thermal expansion for these blends were close to that of pure LCP.
A numerical model for single screw extrusion with poly(vinyl chloride) (PVC) resins
Authors: Thibault F. , Tanguy P. A. , Blouin D. 
Published: May 2005

AbstractA computer model has been developed to simulate the behavior of molten polymer in the melt conveying zone of extruders. This model, based on a hybrid finite difference/finite element resolution of the equations of change governing momentum and heat transfer, allows the prediction of the pressure profile while accounting for wall end effects as well as the solid bed velocity. Simulation results are compared with analytical and finite difference method results found in the literature. A fairly good agreement is obtained in the case of low density polyethylene. Numerical tests are also carried out with rigid poly(vinyl chloride) compound used for window profile extrusion. The good agreement found between the predictions and experimental measurements obtained on an industrial extruder confirms the performance of the proposed model.