Thu, 07 Aug 2008 21:36:15 BST CiteULike: 6rheology's library [796 articles] http://www.citeulike.org/user/6rheology CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/6rheology/article/3090186 <i>Polymer Engineering & Science, Vol. 18, No. 12. (1978), pp. 973-984.</i><br /><br />The cross section geometry of fully wiped corotating twin screws is derived from simple kinematic principles. A pair of screws can have identical cross sections with each screw running at the same speed, or they can have an unequal number of tips and rotate at different speeds. The more conventional case of equal cross section is reviewed in detail, showing how screw diameter, centerline distance, lead, and number of tips influences design, net volumes, and surface areas. The screw cross section is unique for a given diameter, centerline distance, and number of tips. The construction of the cross section is shown, both for pairs of identical screws, and for screws with a speed ratio. Maps are provided to show applicability of screws with 1, 2, and 3 tips. Geometry of fully wiped twin-screw equipment ML Booy doi:10.1002/pen.760181212 Polymer Engineering & Science, Vol. 18, No. 12. (1978), pp. 973-984. 2008-08-06T07:44:21-00:00 1978 Polymer Engineering & Science 18 12 973 984 geometry twin-screw_extruder http://www.citeulike.org/user/6rheology/article/3089902 <i>Japan J. Indust. Appl. Math., Vol. 18, No. 2. (2001), pp. 613-626.</i> Lagrangian Chaos and Mixing of Fluids M Funakoshi Japan J. Indust. Appl. Math., Vol. 18, No. 2. (2001), pp. 613-626. 2008-08-06T04:30:14-00:00 2001 Japan J. Indust. Appl. Math. 18 2 613 626 chaos mixing http://www.citeulike.org/user/6rheology/article/487557 <i>The Journal of Chemical Physics, Vol. 103, No. 19. (1995), pp. 8577-8593.</i><br /><br />The previously developed particle mesh Ewald method is reformulated in terms of efficient B-spline interpolation of the structure factors. This reformulation allows a natural extension of the method to potentials of the form 1/rp with p" align="bottom">1. Furthermore, efficient calculation of the virial tensor follows. Use of B-splines in place of Lagrange interpolation leads to analytic gradients as well as a significant improvement in the accuracy. We demonstrate that arbitrary accuracy can be achieved, independent of system size N, at a cost that scales as N log(N). For biomolecular systems with many thousands of atoms this method permits the use of Ewald summation at a computational cost comparable to that of a simple truncation method of 10 Å or less. ©1995 American Institute of Physics. A smooth particle mesh Ewald method Ulrich Essmann Lalith Perera Max Berkowitz Tom Darden Hsing Lee Lee Pedersen doi:10.1063/1.470117 The Journal of Chemical Physics, Vol. 103, No. 19. (1995), pp. 8577-8593. 2006-01-31T17:51:42-00:00 1995 The Journal of Chemical Physics 103 19 8577 8593 AIP ewald particle_mesh_ewald http://www.citeulike.org/user/6rheology/article/3079483 <i>(1998)</i> 偏心2円筒間の流れにおけるカオス混合 市田良夫 船越満明 (1998) 2008-08-04T05:08:06-00:00 1998 chaos mixing http://www.citeulike.org/user/6rheology/article/3078298 <i>Seikei-Kakou, Vol. 11, No. 4. (1999), pp. 357-364.</i> Morphology Development and Control in Immiscible Polymer Blends Christopher Macosko Seikei-Kakou, Vol. 11, No. 4. (1999), pp. 357-364. 2008-08-03T07:04:52-00:00 1999 Seikei-Kakou 11 4 357 364 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075309 <i>Polymer, Vol. 42, No. 13. (June 2001), pp. 5651-5659.</i><br /><br />A transparent flow cell apparatus has been used to obtain quantitative information on the morphology evolution of a model polymer blend flowing in complex flow fields. A dilute emulsion of poly-dimethylsiloxane droplets immersed in a poly-isobutene matrix, both Newtonian liquids at room temperature, has been chosen as a model system. Optical microscopy coupled with image acquisition analysis allowed to monitor the behavior of droplets flowing through a sudden contraction and through a gradual converging channel followed by a sudden expansion. The experimental results indicate that drop deformation and breakup are sensitive to both shear and extensional components. A simple criterion, based on the evaluation of a local critical capillary number, is proposed to predict the morphological evolution of the flowing blend. By using computer simulations to estimate the velocity gradients in the flow field, it is shown that the proposed criterion is able to successfully predict the observed morphology. Morphology evolution of immiscible polymer blends in complex flow fields Concetta Testa Immacolata Sigillo Nino Grizzuti doi:10.1016/S0032-3861(01)00078-7 Polymer, Vol. 42, No. 13. (June 2001), pp. 5651-5659. 2008-08-02T06:00:49-00:00 2001 Polymer 42 13 5651 5659 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075308 <i>Polymer, Vol. 42, No. 11. (May 2001), pp. 5029-5036.</i><br /><br />This study demonstrates the important role of the compatibilizer in blown films of a ternary blend of a thermotropic liquid crystalline polymer (TLCP (a poly(ester amide)), dispersed phase), a polyetherimide (matrix), and a poly(ester imide) (PEsI, compatibilizer). We investigated the morphology of the blown films via transmission electron microscopy and scanning electron microscopy, as well as optical microscopy. A stripe structure of TLCP phase was observed in the blown film, which evidently showed unequal biaxial deformation of the dispersed phase. The compatibilizer helped to deform the dispersed phase in the hoop direction as well as in the flow direction. It was evident that the amount of compatibilizer played a very important role in the dispersion and the deformation of the TLCP phase. It was found that 0.6 wt% of the compatibilizer was the optimum amount when 10 wt% TLCP was included. Coalescence of the TLCP phase was observed when excessive amount of the compatibilizer was used, resulting in a larger dispersed-phase size. The crystalline structure of the dispersed phase did not vary with the compatibilizer. A qualitative explanation of the effect of the compatibilizer on the deformation of the dispersed droplets is given based on simple droplet elasticity and interfacial tension. Structure development of TLCP ternary blends during biaxial elongational flow Yongsok Seo Jinho Kim doi:10.1016/S0032-3861(00)00862-4 Polymer, Vol. 42, No. 11. (May 2001), pp. 5029-5036. 2008-08-02T05:59:30-00:00 2001 Polymer 42 11 5029 5036 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075307 <i>Polymer, Vol. 41, No. 16. (July 2000), pp. 6263-6270.</i><br /><br />The droplet size distribution during steady shearing of model polymer blends is examined in situ by optical microscopy. The volume-average steady-state droplet size during shear is essentially inversely proportional to shear rate, as expected. When the shear rate is increased suddenly, the droplets break up, through a process that involves the transient formation of threads, and rapidly establish a new steady state, comprising ellipsoidal droplets that are extended slightly in the direction of shear. When the shear is stopped, the droplets quickly relax to a spherical shape, but virtually no coalescence is observed, because neither Brownian nor buoyant forces are significant and the volume fraction of the dispersed phase is low. Slow shear, however, induces droplet collisions that lead to coalescence. The coalescence process is much slower than breakup. In contrast to some predictions, however, there is no permanent droplet size hysteresis. The steady-state size produced by breakup of initially larger droplets is eventually produced at large strain by coalescence of initially smaller droplets. The lack of permanent hysteresis has implications concerning appropriate mathematical models of coalescence behavior. Temporary droplet-size hysteresis in immiscible polymer blends AJ Ramic SD Hudson AM Jamieson I Manas-Zloczower doi:10.1016/S0032-3861(99)00845-9 Polymer, Vol. 41, No. 16. (July 2000), pp. 6263-6270. 2008-08-02T05:58:43-00:00 2000 Polymer 41 16 6263 6270 droplet lab3 pdms-pib peg-ppg http://www.citeulike.org/user/6rheology/article/2644422 <i>Polymer, Vol. 41, No. 14. (June 2000), pp. 5165-5171.</i><br /><br />Dynamic shear moduli of multibranched polystyrenes were measured as functions of frequency and temperature using a parallel-plate rheometer. The multibranched polystyrenes are poly(macromonomer)s of [omega]-methacryloyloxyethyl polystyrene macromonomers (MA-PSt)s and statistical copolymers of the MA-PSt with methyl methacrylate (MMA) monomer. The master curve of the storage dynamic shear modulus G' for the poly(macromonomer)s did not show the so-called plateau region and the G' gradually decreased from the edge of the glass transition region to the terminal zone and the loss modulus G” was always larger than G'. The plateau region became clear in the copolymers with less branch density. These results indicate that the intermolecular chain entanglement might be strongly restricted in the poly(macromonomer) systems due to the multibranched structure of high branch density, which also explains the brittle property of the poly(macromonomer) films. Bulk properties of multibranched polystyrenes from polystyrene macromonomers: rheological behavior I S Namba Y Tsukahara K Kaeriyama K Okamoto M Takahashi doi:10.1016/S0032-3861(99)00744-2 Polymer, Vol. 41, No. 14. (June 2000), pp. 5165-5171. 2008-04-09T11:40:15-00:00 2000 Polymer 41 14 5165 5171 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075306 <i>Polymer, Vol. 41, No. 8. (April 2000), pp. 3057-3068.</i><br /><br />Stress-strain behavior coupled with fractography was used to investigate the weld line strength of 30/70 w/w poly(vinyl chloride)/high density polyethylene (PVC/HDPE) blends. The weld line strength determined in uniaxial tension depended upon the domain shape of the PVC phase at the weld line, with elongated domains causing weld line weakness. To alter the PVC domain shape, the viscosity ratio ([eta]PVC/[eta]HDPE) of the blend was varied by changing the PVC molecular weight. The domain shape at the fracture initiation site was used in conjunction with a modified Nielsen approach to predict the ductile to brittle transition at the weld line. For the composition studied, a critical aspect ratio of the PVC phase of 1.24 was determined. Elongation of the PVC domains above this critical value led to brittle weld lines. The domain shape at the weld line was modeled by a Taylor analysis of droplet deformation in an elongational flow field. The calculations predicted that a viscosity ratio of 21 would produce a particle with an aspect ratio of 1.24. The observed weld line strength confirmed this prediction: blends with a viscosity ratio below 21 were brittle, and those with a viscosity ratio above 21 had ductile weld lines. Weld line strength of poly(vinyl chloride)/polyethylene blends D Jarus JW Summers A Hiltner E Baer doi:10.1016/S0032-3861(99)00470-X Polymer, Vol. 41, No. 8. (April 2000), pp. 3057-3068. 2008-08-02T05:56:50-00:00 2000 Polymer 41 8 3057 3068 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075305 <i>Polymer, Vol. 40, No. 24. (November 1999), pp. 6651-6659.</i><br /><br />The morphology of blends of polystyrene and polyethylene prepared by single screw extrusion and static mixing is shown to consist initially of sheets, which subsequently break up into droplets or threads. The rapid decrease of phase dimensions during blending can quantitatively be described by deformation of sheets in shear flow and not by deformation of droplets into threads. The final phase dimensions are found to be largely determined by the sheet thickness at the onset of break-up of the sheets. The type of morphology obtained after break-up can change during further processing without changing the phase dimensions significantly. At high values of the capillary number threads remain stable, whereas at low values droplets are formed. The final phase sizes appear to be almost independent of the capillary number. Morphology development in immiscible polymer blends: initial blend morphology and phase dimensions RC Willemse EJJ Ramaker J van Dam Posthuma doi:10.1016/S0032-3861(99)00038-5 Polymer, Vol. 40, No. 24. (November 1999), pp. 6651-6659. 2008-08-02T05:56:00-00:00 1999 Polymer 40 24 6651 6659 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075304 <i>Polymer, Vol. 40, No. 10. (May 1999), pp. 2869-2872.</i><br /><br />The rheological characteristics of a particle-suspended Boger fluid are reported. Non-shear thinning, highly elastic polymer solutions were obtained from a mixture of high-molecular-weight polyisobutylene (PIB) and low-molecular-weight polybutene (PB). Kaolinite was chosen as the suspended particles. The shear viscosity and first normal stress difference of the kaolinite-suspended PIB/PB solution exhibit characteristics similar to those of Boger fluids. In contrast to polymer melts with nearly spherical particles, the elasticity of this system increases with the addition of particles, and a qualitative interpretation based on PB (the solvent) as a [`]shielding' agent is given. Rheological properties of particle suspensions in a polymeric liquid Hyoung Choi Vinay Myung Jhon doi:10.1016/S0032-3861(98)00498-4 Polymer, Vol. 40, No. 10. (May 1999), pp. 2869-2872. 2008-08-02T05:55:22-00:00 1999 Polymer 40 10 2869 2872 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075303 <i>Polymer, Vol. 39, No. 23. (November 1998), pp. 5731-5737.</i><br /><br />Linear conservative dichroism has been investigated as a potential tool for tracking (in situ and in real time) the flow-induced microstructure of immiscible polymer blends. Dilute mixtures of poly(dimethylsiloxane) in poly(isobutene) and vice versa have been used as model systems. It is demonstrated that different mechanisms for structural changes can be identified with this technique: droplet deformation, droplet retraction, fibril break-up and coalescence. Time-resolved in-situ SALS measurements support the structural interpretation of the dichroism data. Breaking up of stretched filaments by Rayleigh instabilities can be deduced from dichroism measurements. The resulting strings of droplets can be detected with SALS. The time scales for the structural changes can be determined by dichroism, which makes it possible to study in situ the effect of the various process and material parameters. As an illustration, the effect of shear rate on fibril break-up and on droplet coalescence after sudden changes in shear rate has been considered. Break-up times decreased only slightly with increasing shear rate; coalescence times scaled with the square of shear rate rather than with strain under the conditions of the present experiments. Rheo-optical investigation of immiscible polymer blends Hong Yang Hongjian Zhang Paula Moldenaers Jan Mewis doi:10.1016/S0032-3861(98)00018-4 Polymer, Vol. 39, No. 23. (November 1998), pp. 5731-5737. 2008-08-02T05:53:44-00:00 1998 Polymer 39 23 5731 5737 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075301 <i>Polymer, Vol. 38, No. 8. (April 1997), pp. 1787-1808.</i><br /><br />The development of phase morphology in non-reactive vs reactive polyamide blends with a styrene acrylonitrile (SAN) copolymer and SEBS (a styrenic triblock copolymer with ethylene-butylene midblocks) in a co-rotating twin screw extruder was investigated using electron microscopy techniques. For the polyamide/SAN systems, significant differences were observed between the evolution of morphology in non-reactive binary blends vs blends compatibilized with a reactive imidized acrylic (IA) polymer which is miscible in the SAN phase and has functional groups which are capable of reacting with the amine end groups in the polyamide phase. While a steady decrease in the dispersed phase particle size was observed in general for the non-reactive nylon 6/SAN blends with both increasing screw length and speed, for the ternary nylon 6/SAN/IA blends a dramatic drop in the dispersed phase particle size was observed in the initial region of the screw almost immediately after melting of the pellets followed by some coalescence of dispersed phase in the latter stages leading to a dual population of particle at the exit of the extruder. The extent and onset of coalescence after attainment of minimum particle size in the initial region of the screw in reactive nylon 6/SAN blends was found to be strongly dependent on the screw speed and configuration. The extent of chemical reaction along the extruder screw for reactive nylon 6/SAN blends was dependent on the screw speed, extruder configuration and flow rate. While similar differences in the evolution of morphology were observed between non-reactive and reactive polyamide/SEBS systems, changing the polyamide type from monofunctional (nylon x, e.g. nylon 6) to difunctional (nylon x, y, e.g. nylon 6,6) revealed interesting differences even within these reactive blends. Significant differences in both the development of morphology and reaction profile along the screw were also observed between binary and ternary nylon 6/rubber blends containing similar concentrations of reactive maleic anhydride functionality in the rubber phase using a fixed screw speed and configuration. Evolution of morphology in compatibilized vs uncompatibilized polyamide blends B Majumdar DR Paul AJ Oshinski doi:10.1016/S0032-3861(96)00702-1 Polymer, Vol. 38, No. 8. (April 1997), pp. 1787-1808. 2008-08-02T05:50:16-00:00 1997 Polymer 38 8 1787 1808 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075296 <i>第１５回数値流体力学シンポジウム (2001), B14-5.</i> 二相系格子ボルツマン法によるせん断流中の液滴の変形・分裂シミュレーション Lattice Boltzmann Simulations of Drop Deformation and Breakup in Shear Flows 稲室隆二 冨田隆治 荻野文丸 第１５回数値流体力学シンポジウム (2001), B14-5. 2008-08-02T05:34:47-00:00 2001 第１５回数値流体力学シンポジウム B14-5 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075284 <i>北海道立理科教育センター　研究紀要, No. 12. (2000), 42.</i> 高分子物質の教授プランについて実践的研究 --人間との関わりを通して学ぶ高分子物質-- 八島弘典 北海道立理科教育センター　研究紀要, No. 12. (2000), 42. 2008-08-02T05:25:43-00:00 2000 北海道立理科教育センター　研究紀要 12 42 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075280 <i></i> Simulation of drop coalescence and breakup in 3D viscous flows IB Bazhlekov FN van de Vosse HEH Meijer 2008-08-02T05:20:06-00:00 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075277 <i>化学工学論文集, Vol. 2, No. 3. (1976), 243.</i> 単純剪断場における液滴の変形および分裂 伊藤龍象 平田雄志 石原一彦 重信多三夫 三上公一 秋山武康 化学工学論文集, Vol. 2, No. 3. (1976), 243. 2008-08-02T05:18:01-00:00 1976 化学工学論文集 2 3 243 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075269 <i>日本化学会情報化学部会誌, Vol. 20, No. 3. (2002), 88.</i> 高分子からみあい系分子ダイナミクス高速計算手法ＮＡＰＬＥＳ 増渕 雄一 日本化学会情報化学部会誌, Vol. 20, No. 3. (2002), 88. 2008-08-02T05:06:17-00:00 2002 日本化学会情報化学部会誌 20 3 88 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075231 <i>Journal of Physical and Chemical Reference Data, Vol. 1, No. 4. (1972), 841.</i> The Surface Tension of Pure Liquid Compounds Joseph Jasper Journal of Physical and Chemical Reference Data, Vol. 1, No. 4. (1972), 841. 2008-08-02T03:35:08-00:00 1972 Journal of Physical and Chemical Reference Data 1 4 841 data droplet lab3 surface_tension http://www.citeulike.org/user/6rheology/article/3075225 <i>成形加工, Vol. 11, No. 4. (1999), pp. 357-364.</i> Morphology Development and Control in Immiscible Polymer Blends Christopher 成形加工, Vol. 11, No. 4. (1999), pp. 357-364. 2008-08-02T03:28:56-00:00 1999 成形加工 11 4 357 364 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075191 <i>Polymer Engineering & Science, Vol. 42, No. 4. (2002), pp. 798-809.</i><br /><br />The influence of elasticity of the blend constituent components on the size and size distribution of dispersed-phase droplets is investigated for blends of polystyrene and high density polyethylene in a simple shearing flow. The elasticities of the blend components are characterized by their first normal stress differences. The role played by the ratio of drop to matrix elasticity at fixed viscosity ratio was examined by using high molecular weight polymer melts, high density polyethylene and polystyrene, at temperatures at which the viscosity ratios roughly equaled each of three different values: 0.5, 1, and 2. The experiments were conducted by using a cone-and-plate rheometer, and the steady-state number and volume-mean averages of droplet diameters were determined by optical microscopy. After steady-state shearing, the viscoelastic drops were larger than the Newtonian drops at the same shearing stress. From the steady-state dispersed-phase droplet diameters, the steady-state capillary number, Ca, defined as the ratio of the viscous shearing stress over the interfacial tension stress, was calculated as a function of the ratio of the first normal stress differences in the droplet and matrix phases. For the blend systems with viscosity ratio 0.5, 1 and 2, the values of steady-state capillary number were found to increase with the first normal stress difference ratio and followed a power law with scaling exponents between 1.7 and 1.9. Influence of elasticity on dispersed-phase droplet size in immiscible polymer blends in simple shearing flow Wanchai Lerdwijitjarud Anuvat Sirivat Ronald Larson doi:10.1002/pen.10992 Polymer Engineering & Science, Vol. 42, No. 4. (2002), pp. 798-809. 2008-08-02T02:43:27-00:00 2002 Polymer Engineering & Science 42 4 798 809 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075190 <i>Polymer Engineering & Science, Vol. 40, No. 2. (2000), pp. 357-364.</i><br /><br />Three-dimensional nonisothermal flow simulations in the kneading disc regions of co-rotating twin screw extruders were performed using a finite element method. The standard Galerkin method and penalty function scheme were applied to the flow field. The streamline-upwind/Petrov-Galerkin scheme was used in the temperature field to reduce numerical oscillation. The simulations were carried out under the operational conditions of The Japan Steel Works TEX30 machine for various rotational speeds. The configuration was ten 2-lobe kneading discs with a 90° stagger angle. Experimental observations were also performed to validate the numerical simulations under the same operational conditions. The pressure in front of the tip in the rotation direction was higher than behind the tip, and the region behind the tip sometimes had a negative value. Since variation of the pressure gradient in the axial direction causes forward and backward flows in the disc gap regions, the disc gap regions play an important role for mixing. The temperature becomes higher with increasing rotation speed due to high viscous dissipation. A high temperature was observed on the disc surface, in the disc gap, and in the intermeshing regions. The numerical results of pressure profiles with the rotation and the temperature in the axial direction were in good agreement with the experimental observations. 3-D numerical simulations of nonisothermal flow in co-rotating twin screw extruders Takeshi Ishikawa Shin-Ichi Kihara Kazumori Funatsu doi:10.1002/pen.11169 Polymer Engineering & Science, Vol. 40, No. 2. (2000), pp. 357-364. 2008-08-02T02:42:10-00:00 2000 Polymer Engineering & Science 40 2 357 364 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075188 <i>Polymer Engineering & Science, Vol. 39, No. 2. (1999), pp. 286-298.</i><br /><br />A series of experiments was conducted to determine what correlations exist between an experimental parameter, percent drag flow, and other parameters such as head, tail and mean residence time. Experimentation was carried out on two polymer systems, a model system of near-Newtonian fluid and a viscoelastic system of polyisoprene with several additives. To aid in the residence time analysis, data from three literature sources were cited and replotted. A family of residence time curves for a partially filled system can be combined into one curve by plotting the number of screw revolutions carrying the tracer to the extruder exit versus the percent drag flow. This method of plotting the data for each screw configuration estimates the mean residence time for any throughput and screw speed once a few data points are taken. In all four sets of experiments, the number of screw revolutions carrying the tracer to the exit decreases with increasing percent drag flow. The filled volume of the extruder was calculated from residence time data to show that percent drag flow is linearly related to extruder filled volume. When percent drag flow increased in the viscoelastic system the following results were recorded: fraction of polymer residence time spent in conveying elements increased, fraction of residence time spent in mixing elements decreased, polymer Mooney viscosity increased, number and weight average molecular weights increased and polydispersivity increased. A new approach to analyzing residence time and mixing in a co-rotating twin screw extruder Glenn Gasner David Bigio Charles Marks Fredrick Magnus Christopher Kiehl doi:10.1002/pen.11415 Polymer Engineering & Science, Vol. 39, No. 2. (1999), pp. 286-298. 2008-08-02T02:39:06-00:00 1999 Polymer Engineering & Science 39 2 286 298 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075187 <i>Polymer Engineering & Science, Vol. 38, No. 11. (1998), pp. 1898-1905.</i><br /><br />The effect of shear level on the structure and resultant resistivity of CB-containing high impact polystyrene/linear low density polyethylene (HIPS/LLDPE) extrudates produced by a capillary rheometer, as a function of blend composition and CB content, was studied. The data were compared with results obtained by various processing methods such as compression molding, extrusion, and injection molding. The conductivity of systems consisting of a single polymer matrix is more sensitive to shear rate than are those with HIPS/LLDPE matrices. Increased temperature tends to increase resistivity at high shear rates, and has practically no effect at low shear rates. Capillary entrance effects determine the CB structure and resultant resistivity of the extrudates. Apparently, the combined effects of CB location and flow-induced structuring may explain the enhanced conductivity of some of the extrudates. Shear rate effect on the resistivity of HIPS/LLDPE/carbon black extrudates O Breuer R Tchoudakov M Narkis A Siegmann doi:10.1002/pen.10360 Polymer Engineering & Science, Vol. 38, No. 11. (1998), pp. 1898-1905. 2008-08-02T02:38:29-00:00 1998 Polymer Engineering & Science 38 11 1898 1905 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075163 <i>Polymer Engineering & Science, Vol. 38, No. 11. (1998), pp. 1781-1792.</i><br /><br />A global computation model for self-wiping corotating twin screw extruders is proposed. Based on a ID approximated approach, it has been validated by comparison with experimentation and more sophisticated numerical models. It allows one to obtain, for any screw profile including left-and right-handed screw elements and kneading discs, the profile along the screws of the main flow variables, such as pressure, mean temperature, residence time, and filling ratio. Owing to the approximations made, this model can be easily and rapidly run on a personal computer or a workstation. Important applications may be found in screw profile design, scaleup, compounding or reactive extrusion. A global computer software for polymer flows in corotating twin screw extruders B Vergnes G Della Valle L Delamare doi:10.1002/pen.10348 Polymer Engineering & Science, Vol. 38, No. 11. (1998), pp. 1781-1792. 2008-08-02T02:04:41-00:00 1998 Polymer Engineering & Science 38 11 1781 1792 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075162 <i>Polymer Engineering & Science, Vol. 38, No. 10. (1998), pp. 1751-1762.</i><br /><br />Most of the morphology development in compounding of immiscible blends is known to occur at short mixing times. In this investigation, the effect of rheology of the minor component on its tendency to form a continuous phase at short mixing times is studied. it was shown that phase inversion during compounding can occur even with a low-melting major component. Four different blends with polyethylene as the high-melting-point minor component and polycaprolactone as the low-melting-point major component were chosen. Rheological measurements on the individual components were made both in the solid and melt states. Softening temperatures from these measurements were more representative of the observed processing behavior than the peak values as calculated from differential scanning calorimetry data. Compounding runs in a batch intensive mixer indicated that the minor component formed the continuous phase at short mixing times, in the blends with the low viscosity polyethylene. This was shown to correlate with its low modulus in the solid state and its low viscosity in the melt. A ramped temperature protocol during compounding delayed the melting of polyethylene thus preventing phase inversion from occurring. The blends with the higher viscosity polyethylene did not show phase inversion during compounding. Phase inversion during compounding with a low melting major component: Polycaprolactone/polyethylene blends Ram Ratnagiri Chris Scott doi:10.1002/pen.10345 Polymer Engineering & Science, Vol. 38, No. 10. (1998), pp. 1751-1762. 2008-08-02T02:02:28-00:00 1998 Polymer Engineering & Science 38 10 1751 1762 droplet lab3 phase_inversion http://www.citeulike.org/user/6rheology/article/3075159 <i>Polymer Engineering & Science, Vol. 38, No. 9. (1998), pp. 1549-1558.</i><br /><br />The velocity field in the screw channels of a co-rotating twin-screw extruder was measured using laser Doppler anemometry. Velocity distributions were measured for two screw elements having pitches of 14 and 28 mm, respectively. The magnitude of radial velocity component for both elements was no more than 10% of the magnitude of total velocity. The radial and the axial velocity components were similar for both screw elements. Wider range of tangential velocity values and steeper gradients near the flights were observed for smaller pitch screw element. Measurement of three-dimensional velocity field in the translational region of a co-rotating twin-screw extruder Serafim Bakalis Mukund Karwe doi:10.1002/pen.10325 Polymer Engineering & Science, Vol. 38, No. 9. (1998), pp. 1549-1558. 2008-08-02T01:58:31-00:00 1998 Polymer Engineering & Science 38 9 1549 1558 droplet experiment lab3 laser_doppler http://www.citeulike.org/user/6rheology/article/3075158 <i>Polymer Engineering & Science, Vol. 38, No. 7. (1998), pp. 1193-1198.</i><br /><br />Current residence time distribution models for counter-rotating extruders are mainly developed for fully filled machines. However, in practical situations, these extruders operate under starved conditions. To overcome this missing link in the current models, this paper describes the average degree of fill in the situation of starvation. This degree of fill is determined by the length over which the extruder is fully filled and the degree of fill in the partially filled zone. The comparison of the experiments with the theory shows that the existing theory underestimates the length of the fully filled zone by about 30%. The degree of fill in the partially filled zone is well predicted by taking into account all non-pressure driven leakage flows. Determination of the degree of fill in a counter-rotating twin screw extruder AJ Van Der Goot O Poorter LPBM Janssen doi:10.1002/pen.10287 Polymer Engineering & Science, Vol. 38, No. 7. (1998), pp. 1193-1198. 2008-08-02T01:56:37-00:00 1998 Polymer Engineering & Science 38 7 1193 1198 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075156 <i>Polymer Engineering & Science, Vol. 38, No. 7. (1998), pp. 1112-1120.</i><br /><br />The effects of dissolved supercritical carbon dioxide on the viscosity and morphological properties were investigated for polyethylene/polystyrene blends in a twin-screw extruder. The viscosities of the blend/CO2 solutions were measured using a wedge die mounted on the extruder. A considerable reduction of viscosity was found when CO2 was dissolved in the blend. It was observed that the dissolution of CO2 into PE/PS blends, regardless of the CO2 content used, led to decreased shear thinning behavior resulting in an increase of the power law index from 0.29 to 0.34. The cell structures of foamed PE/PS blends showed a typical dependence of pressure and CO2 concentration, with higher operating pressures and CO2 content leading to a smaller cell size. Also, it was noted that the size of the dispersed PS phase in the PE/PS phase blends decreased by increasing the CO2 concentration, and that the dispersed PS phase domains were highly elongated in the direction normal to the cell radius. Extrusion of PE/PS blends with supercritical carbon dioxide Minhee Lee Costas Tzoganakis Chul Park doi:10.1002/pen.10278 Polymer Engineering & Science, Vol. 38, No. 7. (1998), pp. 1112-1120. 2008-08-02T01:56:00-00:00 1998 Polymer Engineering & Science 38 7 1112 1120 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075155 <i>Polymer Engineering & Science, Vol. 38, No. 6. (1998), pp. 936-946.</i><br /><br />The axial discharge continuous mixer combines the features of a continuous mixer and a twin screw extruder, expanding the flexibility of this compounding machine. In this work we analyzed the influence of rotor design on the dispersive mixing performance of a LCMAX 40 unit. Specifically we looked at various arrangements for the pushing and counter pushing units in the design of the LCMAX 40. A fluid dynamics analysis package - FIDAP, based on the finite element method, was used to model the flow behavior of a power law model fluid under different pressurization conditions. Dispersive mixing efficiency was quantified in terms of shear stresses and elongational flow components generated in the flow field. We found that the counter-pushing unit generally contributes more in building up high shear stresses. However, the generation of elongational flow components, which is beneficial for dispersive mixing, is not solely dependent upon the pushing-counter pushing configuration but rather on the overall rotor geometry. We found that the maximum number of counter-pushing units in the rotor design of the LCMAX 40 should not exceed two in order to provide adequate material pumping. Rotor designs with alternating arrangements of pushing and counter-pushing units provide overall better dispersive mixing conditions. Influence of design on dispersive mixing performance in an axial discharge continuous mixer - LCMAX 40 Chih-Hsiang Yao Ica Manas-Zloczower doi:10.1002/pen.10261 Polymer Engineering & Science, Vol. 38, No. 6. (1998), pp. 936-946. 2008-08-02T01:54:41-00:00 1998 Polymer Engineering & Science 38 6 936 946 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075153 <i>Polymer Engineering & Science, Vol. 38, No. 3. (1998), pp. 485-498.</i><br /><br />Extensive experimental studies of a starved flow modular tangential screw extruder are described. Die pressures and fill factor profiles along the screw axis are measured and used to determine screw characteristic curves Q vs. DeltaP/L for individual screw elements of varying designs in a Leistritz twin screw extruder. Superior pumping characteristics of matched as opposed to staggered elements is found. The experimental screw characteristic curves are compared with the results of mathematical simulations of the flow. Agreement is generally good. Modular tangential counter-rotating twin screw extrusion: Determination of screw pumping characteristics of modules and composite machine behavior Dae-Suk Bang Myung-Hyuk Hong James White doi:10.1002/pen.10211 Polymer Engineering & Science, Vol. 38, No. 3. (1998), pp. 485-498. 2008-08-02T01:52:53-00:00 1998 Polymer Engineering & Science 38 3 485 498 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075152 <i>Polymer Engineering & Science, Vol. 37, No. 9. (1997), pp. 1512-1525.</i><br /><br />Breakup of fibers of a thermotropic liquid crystalline polymer (TLCP) above the melting temperature in various ordinary polymers has been studied by capillary instability experiments on single TLCP fibers and by annealing experiments on extruded TLCP/thermoplast blends. The TLCP was an aromatic copolyester, Vectra A900, the matrix polymers were PP, PS, PC, PEL PES, and PEBT. Both types of experiments show that the fiber/matrix morphology is, in general, highly unstable in the molten state. The TLCP fibers break up into droplets by a combination of Rayleigh distortions, end-pinching and retraction, depending on the system and shape of the fiber. Fibers of a thickness of sim1 mum can break up in a few seconds. Breakup times of fibrous blends and individual fibers are in agreement provided size effects are accounted for. Rayleigh distortions develop exponentially in time up to relative distortions of 0.5 to 0.6. Breakup occurs within a range of wave numbers rather than at one distinct dominant wave number, which is shown to be the consequence of relatively large initial distortions. Apparent values for the interfacial tensions calculated with Tomotika's theory turned out to be of the correct order of magnitude, ranging from 7 mN/m for Vectra/PES to 24 mN/m for Vectra/PP and to yield correct values of the interfacial tensions of PP/PS, PP/PC, and PS/PC using Antonow's rule. Stability of blends of thermotropic liquid crystalline polymers with thermoplastic polymers AGC Machiels J Van Dam Posthuma De Boer B Norder doi:10.1002/pen.11800 Polymer Engineering & Science, Vol. 37, No. 9. (1997), pp. 1512-1525. 2008-08-02T01:49:57-00:00 1997 Polymer Engineering & Science 37 9 1512 1525 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075151 <i>Polymer Engineering & Science, Vol. 37, No. 6. (1997), pp. 1082-1090.</i><br /><br />Co-rotating twin-screw extruders are widely used for compounding and blending in polymer processing. In a modular machine, the dominant elements determining dispersive mixing efficiency are the kneading discs. A fluid dynamics analysis package - FIDAP, using the finite element method was implemented to simulate the 3-D isothermal flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK-53 co-rotating twin-screw extruder. The kneading discs simulated are three-lobe discs. The flow field characteristics relevant for dispersive mixing are shear stresses generated and elongational flow components. We compare these flow characteristics for the three-lobe kneading discs of the ZSK-53 with the two-lobe discs of a ZSK-30 machine. We also discuss the influence of processing parameters on the flow field mixing efficiency. Study of mixing efficiency in kneading discs of co-rotating twin-screw extruders Hongfei Cheng I Manas-Zloczower doi:10.1002/pen.11753 Polymer Engineering & Science, Vol. 37, No. 6. (1997), pp. 1082-1090. 2008-08-02T01:48:15-00:00 1997 Polymer Engineering & Science 37 6 1082 1090 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075150 <i>Polymer Engineering & Science, Vol. 37, No. 6. (1997), pp. 994-1002.</i><br /><br />We report the results of a study of droplet deformation in uniaxial elongational flow under nonisothermal conditions. A mathematical model is developed that simulates deformation conditions in fiber spinning. To test our model, a blend of polypropylene and polystyrene was spun into fibers. The blend morphology of the fibers is accurately predicted by the proposed model. Morphological studies have shown that immiscible additives remain dispersed in the matrix as suspended droplets and that the droplets are elongated into fibrils under the action of shear or extensional forces during processing. Modeling droplet deformation in melt spinning of polymer blends AD Padsalgikar MS Ellison doi:10.1002/pen.11744 Polymer Engineering & Science, Vol. 37, No. 6. (1997), pp. 994-1002. 2008-08-02T01:47:42-00:00 1997 Polymer Engineering & Science 37 6 994 1002 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075149 <i>Polymer Engineering & Science, Vol. 37, No. 3. (1997), pp. 511-518.</i><br /><br />This article describes the radical copolymerization of styrene (St) and n-butyl-methacrylate (BMA) in a counter-rotating twin-screw extruder. In order to investigate the effect of the polymer melt viscosity on the working domain in reactive extrusion, the copolymer was crosslinked with different amounts of divinylbenzene (DVB). Crosslinking of the polymer resulted in a higher polymer melt viscosity. It was demonstrated that not only the product properties but also the process characteristics were strongly influenced by the addition of divinylbenzene to the reaction mixture. The product properties changed as expected: more crosslink agent led to a higher molecular weight or an increase in gel fraction, and a much higher melt viscosity of the polymer. Besides these effects on the product properties, the addition of DVB resulted in a more stable process, leading to an enlarged working domain. The working domain in reactive extrusion. Part I: The effect of the polymer melt viscosity AJ van der Goot R Hettema LPBM Janssen doi:10.1002/pen.11694 Polymer Engineering & Science, Vol. 37, No. 3. (1997), pp. 511-518. 2008-08-02T01:46:56-00:00 1997 Polymer Engineering & Science 37 3 511 518 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075147 <i>Polymer Engineering & Science, Vol. 36, No. 19. (1996), pp. 2451-2466.</i><br /><br />This paper describes the preparation and properties of in-situ composites based on polymers with no overlap in processing temperatures. The polymers used were Vectra A900, a thermotropic liquid crystalline copolyester (TLCP), and Arnitel em630, a thermoplastic elastomer. Blends were generated by feeding the two components from separate extruders into a Ross static mixer. Different morphologies were obtained by varying the number of mixing elements of the static mixer. Using 8 mixing elements led to a stratified morphology of Vectra layers in Arnitel, using 11 mixing elements resulted in the desired continuous fiber/matrix morphology whereas a pronounced skin-core morphology was obtained with 14 mixing elements. It is argued that in-situ composites can be generated by a distributive mixing process without the formation of an intermediate droplet/matrix morphology as occurs in common dispersive blending equipment. Tensile modulus and strength of all blends increased with extrudate draw ratio as a result of increased molecular orientation of the TLCP phase. The level of reinforcement, however, was lower than expected, probably due to the low temperature of drawing. Annealing and capillary instability experiments showed that above the melting point of the TLCP the fiber/matrix morphology rapidly breaks up into a droplet/matrix morphology. This process takes just a few seconds for fibers of thickness sim 1 mum. It is shown to be the probable cause of the skin-core morphology obtained in case of 14 mixing elements. Formation, stability, and properties of <I>in</I>-<I>situ</I> composites based on blends of a thermotropic liquid crystalline polymer and a thermoplastic elastomer AGC Machiels KFJ Denys J Van Dam Posthuma De Boer doi:10.1002/pen.10643 Polymer Engineering & Science, Vol. 36, No. 19. (1996), pp. 2451-2466. 2008-08-02T01:46:15-00:00 1996 Polymer Engineering & Science 36 19 2451 2466 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075145 <i>Polymer Engineering & Science, Vol. 36, No. 13. (1996), pp. 1769-1781.</i><br /><br />When polymer blends are prepared from a mixture of pellets, the melting order of the components is important in determining the mechanism of morphology development. Here, we show that an inversion of phase continuity occurs during processing when a minor phase component has a softening or melting transition temperature which is lower than the softening temperature of the major phase component. Three 80:20 concentration systems were studied: polyarylate/rubber, polyamide 6,6/polystyrene, and polystyrene/ethylene propylene rubber. Initially, the minor phase was the continuous phase and coated the major phase in all three systems. As the major phase melted, a switching of phase continuity occurred, and in the final blend state, the major phase was the continuous phase. An increase in power input was required during the switching of the dispersed and matrix phases. The compounding process was studied through continuous video monitoring, torque-temperature analysis, and microscopy of quenched samples. A continuity inversion mechanism is proposed. It is found that the initial morphology of the blend consists of sheets of the major phase inside the minor phase. These sheets break up into irregularly shaped particles, which then coalesce around the minor phase. The effects of compatibilization (using reactive polymers or adding a premade diblock) on the rheology and morphology of the blend are also investigated. Interfacial reaction is seen to delay and intensify the inversion of phase continuity, whereas addition of premade diblock does not have any significant effect. The torque increases due to interaction of the major phase domains and due to reactive stabilization of the interface against coalescence, and the contributions of each to the torque can be decoupled. Evidence for inversion of phase continuity during morphology development in polymer blending Uttandaraman Sundararaj CW Macosko Chi-Kai Shih doi:10.1002/pen.10572 Polymer Engineering & Science, Vol. 36, No. 13. (1996), pp. 1769-1781. 2008-08-02T01:44:18-00:00 1996 Polymer Engineering & Science 36 13 1769 1781 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075144 <i>Polymer Engineering & Science, Vol. 36, No. 12. (1996), pp. 1694-1706.</i><br /><br />This paper examines the mechanisms by which a polymer is dispersed in a co-rotating twin-screw extruder. An experimental investigation of the morphological evolution has been carried out on a 45-mm co-rotating twin-screw extruder. Polyethylene/polystyrene (PE/PS) blends in the low concentration range (i.e., 5-15 wt% of PE) were used as a model system. The following general trends were observed. First, the minor phase right after melting is predominantly in a fibrillar form. Secondly, droplet and fiber diameter at this early stage of compounding are already in the micron or sub-micron range. Even though a wide variety of mixing section configurations were used, the fibers created in the early compounding stages were relatively stable throughout extrusion. Morphological evolution after melting must therefore be discussed in terms of variation in the fiber fraction (i.e., fiber to droplet transition) rather than in a change in particle diameter. A control volume model for the flow in kneading blocks is used to interpret the morphological results and to predict the deformation and breakup of dispersed phase fibers under shear and in absence of coalescence. Theoretical results indicate that fiber breakup under shear is not likely in the kneading block under the normal processing conditions, which is confirmed by morphological observations made at the mixing section exit. The influence of several geometrical parameters on mixing and pumping in kneading blocks is also discussed with the use of flow model results. Polymer blend mixing and dispersion in the kneading section of a twin-screw extruder MA Huneault MF Champagne A Luciani doi:10.1002/pen.10566 Polymer Engineering & Science, Vol. 36, No. 12. (1996), pp. 1694-1706. 2008-08-02T01:43:12-00:00 1996 Polymer Engineering & Science 36 12 1694 1706 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075143 <i>Polymer Engineering & Science, Vol. 36, No. 12. (1996), pp. 1685-1693.</i><br /><br />The control of the morphology of an immiscible polymer melt is of vital importance for the mastering of the final properties of the product. As polymer blends are produced using corotating twin-screw extruders, understanding and modeling the changes experienced by the blend during this process is of great interest. In the present study, starting from Ludovic software, developed for computing flow parameters in the twin-screw extrusion process, we present a computation of the droplet morphology development, based on the basic mechanisms of break-up and coalescence. Depending on the value of a local capillary number and on local flow conditions, different changes may occur: affine deformation, drop splitting, break-up by capillary instability, and coalescence. It is thus possible to follow, all along the screws, the changes in morphology, either for a single particle or for a particle distribution. Examples of these different computations are presented and compared with experimental results. Generally speaking, orders of magnitude of droplet size and tendencies when modifying processing conditions are correctly described, but the model still suffers from the absence of descrption of the melting process. Computation of the morphological changes of a polymer blend along a twin-screw extruder L Delamare B Vergnes doi:10.1002/pen.10565 Polymer Engineering & Science, Vol. 36, No. 12. (1996), pp. 1685-1693. 2008-08-02T01:42:33-00:00 1996 Polymer Engineering & Science 36 12 1685 1693 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075141 <i>Polymer Engineering & Science, Vol. 36, No. 7. (1996), pp. 912-924.</i><br /><br />Three-dimensional flow simulations of kneading elements in an intermeshing corotating twin-screw extruder are performed by solving the Navier Stokes equations with a finite element package, Sepran. Instead of using the whole geometry of the 8-shaped barrel a simplified geometry is used, representing a large part of the geometry during the rotating action of the kneading paddle. The goal of these calculations is to study the dependence of several factors that influence mixing, such as shear rate, elongation rate, pressure, and the flow profile in the extruder on various extruder parameters, such as fluid viscosity, rotation speed, and throughput.The shear and elongation rate and the pressure drop are calculated for varying viscosities. The various stagger angles possible for disc configurations in the corotating twin-screw extruder are modeled. The axial backflow volume is calculated for varying values of rotation speed and throughput. Three-dimensional flow modeling of a self-wiping corotating twin-screw extruder. Part II: The kneading section DJ Van Der Wal D Goffart EM Klomp HW Hoogstraten LPBM Janssen doi:10.1002/pen.10479 Polymer Engineering & Science, Vol. 36, No. 7. (1996), pp. 912-924. 2008-08-02T01:40:48-00:00 1996 Polymer Engineering & Science 36 7 912 924 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075140 <i>Polymer Engineering & Science, Vol. 36, No. 7. (1996), pp. 901-911.</i><br /><br />A three-dimensional modeling of the transporting elements in a self-wiping corotating twin-screw extruder has been carried out by using the finite element package Sepran (1). This simulation uses the 3D geometry of the channel rolled over the twin-screw, which consists of the intermeshing and normal areas. The flow profile, the backflow volume, the pressure buildup, the shear and elongation rates, and the adiabatic axial temperature gradient have been calculated by solving the Navier-Stokes equations and the continuity equation for a Newtonian fluid. These results are given for different extruder parameters such as the throughput of the extruder, the rotation speed of the screws and the helix angle of the screws to better understand the influence of different extruder configurations. This study belongs to a program of research on the self-wiping corotating twin-screw extruder that also includes the modeling of the kneading elements (Part II) and, in the future, the study of scale-up and heat transfer. Three-dimensional flow modeling of a self-wiping corotating twin-screw extruder. Part I: The transporting section D Goffart DJ Van Der Wal EM Klomp HW Hoogstraten LPBM Janssen L Breysse Y Trolez doi:10.1002/pen.10478 Polymer Engineering & Science, Vol. 36, No. 7. (1996), pp. 901-911. 2008-08-02T01:39:57-00:00 1996 Polymer Engineering & Science 36 7 901 911 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075139 <i>Polymer Engineering & Science, Vol. 36, No. 12. (1996), pp. 1647-1655.</i><br /><br />Polypropylene drops of varying viscosity and elasticity were sheared in a polystyrene matrix. Two transparent, counter-rotating parallel disks provided simple shear flow. By adjusting the speed of one disk the drop center was fixed in the laboratory frame and deformation followed via high magnification video camera. It was found that with high matrix elasticity drops of the minor phase stretched perpendicular (x3) to the flow direction (x1). This is the first report of widening of drops in shear flow. An analytical relation was established between the second normal stress differences of the phases and degree of widening. The formation of sheets and the phenomena of widening results in a larger than affine area generation. Influence of normal stress difference on polymer drop deformation Leon Levitt Christopher Macosko Scott Pearson doi:10.1002/pen.10561 Polymer Engineering & Science, Vol. 36, No. 12. (1996), pp. 1647-1655. 2008-08-02T01:38:56-00:00 1996 Polymer Engineering & Science 36 12 1647 1655 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075138 <i>Polymer Engineering & Science, Vol. 35, No. 23. (1995), pp. 1872-1877.</i><br /><br />The Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic. Theory of competition between breakup and coalescence of droplets in flowing polymer blends Ivan Fortelný Antonín &zcaron;ivný doi:10.1002/pen.760352306 Polymer Engineering & Science, Vol. 35, No. 23. (1995), pp. 1872-1877. 2008-08-02T01:35:19-00:00 1995 Polymer Engineering & Science 35 23 1872 1877 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075136 <i>Polymer Engineering & Science, Vol. 26, No. 6. (1986), pp. 415-417.</i><br /><br />The spinning drop method is used to measure the interfacial tension of molten polymer systems. It proves to be a simple and rather fast measuring method, while satisfactory agreement with literature values, obtained with the pendant drop method, is achieved. Measurement of interfacial tensions of molten polymer systems by means of the spinning drop method JJ Elmendorp G De Vos doi:10.1002/pen.760260607 Polymer Engineering & Science, Vol. 26, No. 6. (1986), pp. 415-417. 2008-08-02T01:33:55-00:00 1986 Polymer Engineering & Science 26 6 415 417 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075135 <i>Polymer Engineering & Science, Vol. 40, No. 2. (2000), pp. 525-541.</i><br /><br />The objective of this work is to validate, via comparison with available experimental data, the results obtained from the numerical simulation of polymer melt flow in the kneading disc section of an intermeshing co-rotating twin screw extruder. A quasi-steady state 3-D solution of the conservation equations via the finite element method was obtained, and comparisons were made with experimental pressure profiles measured by McCullough and Hilton (1) on various kneading block elements. These measurements helped provide understanding of the flow patterns developed within the unit and provided a comprehensive approach of validating the numerical model. Results confirm the importance of a fully 3-D model for this type of geometry, where the model predicts the development of flow patterns in the radial directions and within the intermeshing region. The influence of inlet and outlet boundary conditions was studied and it was determined that they play an important role in the physical significance of the model solution. Comparisons of the simulation results with experimental data by McCullough and Hilton (1) for two different configurations of kneading discs showed good agreement, with some differences in the peaks of pressure produced at the narrow clearances encountered in intermeshing co-rotating twin screw extruders. Differences between simulation and experiments are attributed to a number of factors. It is difficult to measure the very steep pressure gradients generated over small lengths. The assumptions of isothermal flow and quasi-steady state may cause an over-prediction of the pressure peaks. Simulation results describe the general trends and produce good quantitative agreement in most of the kneading disc region. Numerical simulation of pressure and velocity profiles in kneading elements of a co-rotating twin screw extruder VL Bravo AN Hrymak JD Wright doi:10.1002/pen.11184 Polymer Engineering & Science, Vol. 40, No. 2. (2000), pp. 525-541. 2008-08-02T01:32:14-00:00 2000 Polymer Engineering & Science 40 2 525 541 droplet lab3 http://www.citeulike.org/user/6rheology/article/3075133 <i>Polymer Engineering & Science, Vol. 32, No. 24. (1992), pp. 1824-1833.</i><br /><br />The theoretical and experimental data on the breakup of droplets are reviewed. Several factors influence development of droplets: flow type and its intensity, viscosity ratio, elasticity of polymers, composition, thermodynamic interactions, time, etc. For Newtonian systems undergoing small, linear deformation, both the viscosity ratio and the capillary number control deformability of drops. On the other hand, the breakup process can be described by the dimensionless breakup time and the critical capillary number. Drops are more efficiently broken in elongational flow than in shear, especially when the viscosity ratio lambda &ges; 3. The drop deformation and breakup seems to be more difficult in viscoelastic systems than in Newtonian ones. There is no theory able to describe the deformability of viscoelastic droplet suspended in a viscoelastic or even Newtonian medium. The effect of droplets coalescence on the final morphology ought to be considered, even at low concentration of the dispersed phase, &phis;d &ges; 0.005. Several drop breakup and coalescence theories were briefly reviewed. However, they are of little direct use for quantitative prediction of the polymer blend morphology during compounding in a twin-screw extruder. Their value is limited to serving as general guides to the process modeling. Development of polymer blend morphology during compounding in a twin-screw extruder. Part I: Droplet dispersion and coalescence - a review LA Utracki ZH Shi doi:10.1002/pen.760322405 Polymer Engineering & Science, Vol. 32, No. 24. (1992), pp. 1824-1833. 2008-08-02T01:29:40-00:00 1992 Polymer Engineering & Science 32 24 1824 1833 droplet lab3 http://www.citeulike.org/user/6rheology/article/2823956 <i>Macromolecules, Vol. 29, No. 4. (12 February 1996), pp. 1278-1285.</i><br /><br />Abstract: The properties of dendrimers ("starburst" molecules) under varying solvent conditions are studied using molecular dynamics simulations. The dendrimers are found to have a compact (space filling) structure under all solvent conditions, with a radius of gyration which scales with the number of monomers as RG N1/3. For high generation number dendrimers, there is a distinct region of constant monomer density. The density in this region depends only on the solvent quality and is independent of the generation number. When the contributions of the different generations to the overall density profile are separated, we find that the monomers which belong to the first few generations are stretched and spatially localized. Later generations are less localized and penetrate well into the central regions of the dendrimer. The different primary branches ("dendrons") of the dendrimers are found to be segregated. The amount of spatial overlap between the different dendrons decreases with increasing generation number of the dendrimer and increasing solvent quality. The relaxation times of the fluctuations of the internal structure were evaluated as well, to ensure that the simulations were run long enough for adequate sampling. Molecular Dynamics Study of Dendrimer Molecules in Solvents of Varying Quality M Murat GS Grest doi:10.1021/ma951219e Macromolecules, Vol. 29, No. 4. (12 February 1996), pp. 1278-1285. 2008-05-22T19:30:06-00:00 1996 Macromolecules 29 4 1278 1285 lab3 molecular_dynamics polymer_physics http://www.citeulike.org/user/6rheology/article/3070658 <i>Macromolecules, Vol. 29, No. 4. (12 February 1996), pp. 1182-1190.</i><br /><br />Abstract: Size exclusion chromatography (SEC) is a widely used method for determining the molecular weights of polymer molecules. SEC calibration is often achieved using the "universal calibration" technique, which assumes hydrodynamic volume is the sole determinate of retention time. Recent work has demonstrated the failure of this approach when molecular weights are small (<5000) and particularly in the oligomer range. In order to explore the theoretical reasons for this failure, molecular dynamics (MD) simulations have been used to compute the partition coefficients as a function of pore size for oligomeric series of three polymers: polyethylene (PE), polyisobutylene (PIB), and polystyrene (PS). The molecular weight ranges studied were from dimers up to 500 g/mol for PE and up to 1000 g/mol for PIB and PS. MD simulation was used to generate a large number of configurations of the various oligomers. These configurations were then used to compute the partition coefficients of the species in cylindrical pores of varying diameters. The MD model of the oligomers included all atoms explicitly and all internal degrees of freedom. Solvent was not included specifically but the configurations were generated under phantom chain conditions for longer range interactions that are appropriate to the solvent conditions that prevail for short molecules. The variation of partition coefficient with pore size for a given oligomer could be described well by assigning an effective hard-sphere radius, called here the retention radius, to the molecule. The retention radii for an oligomer series were found to correlate well with the radii of gyration. There were however significant differences in the retention radii vs radii of gyration correlations among the three series studied. At the same radius of gyration, the retention radii order is found to be PS > PIB > PE. This order agrees with experimental SEC data for retention times for these oligomer series. The differences are attributed to asphericity of individual configurations enhancing the effects of substituent size. The approach of the mean-square radius of gyration and mean-square end-to-end distance dependence on chain length to limiting long-chain behavior is discussed. It is found that the limiting proportionality to chain length has not been reached in the molecular weight ranges studied. A comparison of the use of the intrinsic viscosity-molecular weight product ([]M) as a measure of radius of gyration, the radius of gyration determined independently, and the retention radius from simulation as criteria for equal retention times is made. The errors in molecular weight determination resulting from the use of each of the three criteria are discussed. The retention radius from simulation is found to be a significantly better criterion for retention time than the []M product or directly determined radius of gyration. Effective Dimensions of Oligomers in Size Exclusion Chromatography. A Molecular Dynamics Simulation Study RH Boyd RR Chance Ver doi:10.1021/ma9508663 Macromolecules, Vol. 29, No. 4. (12 February 1996), pp. 1182-1190. 2008-08-01T08:22:19-00:00 1996 Macromolecules 29 4 1182 1190 lab3 molecular_dynamics polymer_physics http://www.citeulike.org/user/6rheology/article/3070656 <i>Macromolecules, Vol. 28, No. 25. (1995), pp. 8598-8603.</i> Effect of Chain Flexibility on Selectivity in the Gas Separation Process: Molecular Dynamics Simulation Kyoungsei Choi Won Jo Macromolecules, Vol. 28, No. 25. (1995), pp. 8598-8603. 2008-08-01T08:21:25-00:00 1995 Macromolecules 28 25 8598 8603 lab3 molecular_dynamics polymer_physics