bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the Mechanical Properties and Chemical Resistance of PC/PBT/Impact Modifier Blends
Authors: Lyu M.-Y. , Pae Y. , Nah C.
Published: December 2013

Mechanical properties, flow characteristics and chemical resistance of polycarbonate (PC)/poly(butylene terephthalate) (PBT)/impact modifier (IM) blends were investigated over the wide composition range of PC and PBT. Mechanical properties of the PC/PBT/IM blends for two different IMs, butadiene based IM and butyl acrylate based IM, were studied. For the study of chemical resistance of the PC/PBT/IM blends, test specimens were dipped in solvent, thinner, and then variations of mechanical properties were analyzed. Tensile and flexural strengths were increased linearly and heat distortion temperature (HDT) also increased as PC content in the blends increased. Impact strength increased drastically as PC content in the blends increased up to 50 wt.-%, and then it leveled out for over 50 wt.-% of PC. Flowability of the blends decreased as PC content increased. Impact strengths of the blends were different from IMs specially at low temperatures. The blends with butyl acrylate based IM showed slightly higher impact strength than the blends with butadiene based IM at 0°C and room temperature. However, the blends with butadiene based IM showed remarkably higher impact strength than the blends with butyl acrylate based IM at the temperatures below 0°C. After the chemical treatment of test specimens, tensile and flexural strengths decreased, and impact strength increased as PC content in the blends increased. PC in the blends would become mild and ductile when it contacted with solvent, thus the impact strength increased while tensile and flexural strengths decreased.
Effect of Elongational Viscosity on the Flow in a Flat Die
Authors: Sun Y. , Gupta M.
Published: December 2013

The flow of a low-density polyethylene in a flat die is simulated using the axisymmetric and planar elongational viscosities estimated in an earlier publication by Beaupre and Gupta. Elongational viscosity is found to have only a limited effect on the velocity distribution at the die exit. However, the predicted pressure drop in the die and the temperature distribution at the die exit changed significantly when the effect of elongational viscosity was included in the simulation.
Fractionated Crystallization and Morphology in Binary Blends of Isotactic PP and HDPE with Cycloolefin Copolymers
Authors: Pimbert S.
Published: December 2013

Crystallization of binary blends of semi-crystalline polyolefins (i-polypropylene and HD-polyethylenes) and amorphous cycloolefin copolymers (COC) was followed by Differential Scanning Calorimetry (DSC). Blend morphologies were investigated by Scanning Electronic Microscopy (SEM). The thermal behavior and morphology of iPP–COC blends are characteristic of immiscible blends. The two crystallization exotherms observed on cooling from the melt were explained in terms of fractionated crystallization. This phenomenon occurs when iPP inclusions are finely dispersed in the COC matrix so that their number is much greater than the number of heterogeneities originally present in the bulk polymer, resulting in the suppression of the heterogeneous nucleation.

A quite different behavior is observed in PE–COC blends. DSC and DMTA results show a significant decrease of both PE Tm and COC Tg, observations usually associated to some polymer miscibility in the amorphous phase. The crystallization mode and the resulting morphologies also appear to be largely dependent on the molecular weights and polydispersity indices of the dispersed phase.
Die Wall Effects, Contact Angles and Slippage in the Flow of Polymer Melts and Polymer-Particulate Compounds with Carboxylic Acids in a Slit Die
Authors: Ahn S. , White J. L.
Published: December 2013

An experimental study of the influence of carboxylic acid additive in polyethylene/filler and polystyrene/filler compounds in slit die is described. Slit die extrusion experiments and contact angle measurements are reported. A series of fillers of varying particle size including carbon black, calcium carbonate, zinc oxide, and talc are compared. Aliphatic fatty acids, especially octadecanoic acid were used as additives. The greatest viscosity reduction was found in polyethylene/(carbon black) and polystyrene/(calcium carbonate) compounds. Smaller effects are found with the other polyethylene/filler compounds and none in polystyrene/filler compounds. Contact angle experiments indicated carboxylic acid layers on the die surfaces for the polyethylene and not the polystyrene compounds. Mechanisms for this behavior are discussed.
Stretchability and Properties of LLDPE Blends for Biaxially Oriented Film
Authors: Uehara H. , Sakauchi K. , Kanai T. , Yamada T.
Published: December 2013

In order to improve the stretchability of linear low density polyethylene (LLDPE) for double bubble tubular film (DBTF), the blending of LLDPEs have been investigated. Three LLDPEs of varying densities were blended, and several films having different densities, molecular-weight distributions and composition distributions were produced. The stretchability and properties of these films were investigated and the relationship between the stretchability and the material properties were also discussed. The material properties of LLDPE which showed better stretchability were reported. Furthermore, the stretchability of LLDPE by using the laboratory tenter stretched film (LTSF) and the DBTF were compared. The prediction of the stretchability for the DBTF by using the LTSF was reported.
Experimental Investigation of the Development of Interfacial Instabilities in Two Layer Coextrusion Dies
Authors: Valette R. , Laure P. , Demay Y. , Agassant J.-F.
Published: December 2013

The stability of two-layer flow of polyethylene and polystyrene is experimentally studied in different flow geometries and for various flow rate ratios. A first coextrusion device allows to stop the coextrusion flow in a very long slit channel, to cool down the polymer sample and to dismantle the die in order to extract extrudate which is then carefully analyzed.

A second device allows to observe the whole slit flow through transparent lateral walls and to record the interfacial waves in both spontaneous and controlled unstable conditions.

Both devices point clearly out that the interfacial defect begins to grow after a specific flow distance and is then quickly amplified. This demonstrates the convective character of interfacial wave. Controlled unstable processing conditions in transparent die allow to measure accurately growth rate of defect in the linear regime and show quick occurrence of non linear regime.
Detachment of the Polymer Melt from the Roll Surface: Calendering Analysis and Data from a Shear Roll Extruder
Authors: Kalyon D. M. , Gevgilili H. , Shah A.
Published: December 2013

The detachment behavior of a polymer melt from the hot roll surface/s during roll-driven processes affects the maximum production rates achievable in various processes including calendering, embossing and shear roll milling. Here the continuous shear roll milling process is used to investigate the conditions that lead to the detachment of the polymer melt from the surface of one or both heated rolls. During the shear roll milling process the polymer melt needs to continuously stick to one roll and periodically to stick and then to detach from the other roll (at the nip). Different roll speeds, surface roughness and temperatures are used to facilitate continuous stick to one roll and periodic stick and detachment from the other roll. Shear roll mill process fails to convey the melt in the forward direction under conditions for which the melt detaches from both rolls. The shear roll mill processing of a high density polyethylene revealed the detachment of the melt from both rolls under various combinations of operating parameters. A calendering model enabling the use of different roll diameters and roll velocities for incompressible generalized Newtonian fluids under isothermal and lubrication flow conditions was developed and used to understand the detachment dynamics. The detachment of the melt from both rolls was revealed to occur when the maximum shear stress at the roll surface exceeds the critical wall shear stress at which the onset of macroscopic wall slip is observed in simple shear flow. These findings suggest that the processing window for roll-driven processes is affected by the wall slip characteristics of the polymer melt and that the processing window can be widened using a better understanding of the wall slip behavior of the materials being processed.
Dry Spinning of Polymer Fibers in Ternary Systems
Authors: Gou Z. , McHugh A. J.
Published: December 2013

In this work, predictions based on the 2D dry spinning model developed in Part I of this work [2] along with a die swell subroutine supplied by an industrial company, are used to compare with fiber concentration and elongation to break data from an industrial spinline. Die swell ratio predictions agree well with measured values and solidification along the spinline is shown to be due to homogeneous glass transition in the absence of phase separation. Concentration profiles along the spinline are well fit by the model using previously determined prefactors for the diffusion coefficients. A good correlation of elongation at break data is found to occur with a characteristic variable σGTP, the ratio of the rheological force of the viscoelastic Giesekus contribution to the total rheological force (Giesekus + viscous) at the glass transition point. Moreover, the regression obtained from this fit can be further used to make predictions for elongation at break under different operating conditions. Finally, the effects of spinning conditions and model parameters on fiber mechanical properties were investigated.
Simulation of Thermal Phenomena on the Interface Molten Polymer/Powder Polymer During Rotational Molding
Authors: Tcharkhtchi A. , Perrot E. , Chinesta F.
Published: December 2013

In order to simulate the heat transfer phenomenon during rotational molding an alternative approach for the melt front treatment has been used. It was considered that a polymer particle adheres to the inner mould wall or to the polymer layer when the temperature reaches the melting point of polymer. The result of this alternative adhesion of new particles on molten polymer layer is the progress of melt front until all of particle are added to the inner surface of the polymer in the mold.

The simulation was based on an explicit finite volumes scheme which, allows to proceed with a fixed mesh of the whole domain. A numerical test, then, has been performed to illustrate the capabilities of the proposed model. The results of this numerical test showed the temperature evolution of external mold surface, in the molten polymer layer and on the interface molten polymer layer – air/polymer mixture region. These results have been then interpreted.
Parametric Study of the Mixing Efficiency in a Kneading Block Section of a Twin-screw Extruder
Authors: Alsteens B. , Legat V. , Avalosse T.
Published: December 2013

Twin-screw extruders are often used to distribute and disperse additives into polymers. The mixing efficiency of the extruders highly depends on the geometry of the kneading blocks of the mixing section. In this paper, the impact of some geometrical parameters, such as the stagger angle and the width of the discs, are investigated by three dimensional time dependent finite element calculations.

Results are obtained with the finite element software Polyflow. The robustness and the accuracy of the mesh superposition technique is evaluated. It appears that conclusions obtained by the numerical experiments can be used to improve the geometry of the kneading blocks. The mixing efficiency is evaluated by comparing the residence time and the total shear distributions of a large set of virtual particles launched in the flow domain.
Flow Visualization of Filling with Aid of Colored Billets During Impact Micro-Injection Molding
Authors: Nian S. C. , Yang S. Y.
Published: December 2013

Injection molding of thermoplastic parts with micro shot-weight has been developed for many Micro-Electro-Mechanical (MEMS) applications. A lab-made high speed impact type micro-injection machine was developed to perform the micro-injection molding. Many phenomena regarding impact micro-injection molding is not clear and needs systematical investigation. In this study, the filling phenomena during impact micro-injection was observed and investigated. Molds of spiral cavity of four different depths were constructed and employed. One side of the cavity was implemented with transparent window to observe the filling, and the filling phenomena were recorded with a high-speed video camera. To aid detailed observation, in the injection sleeve of the machine, sequential transparent and colored billets were inserted. The recorded images of filling flows of the colored melt in the spiral cavity were used for visualization and analysis of the filling with impact-type micro-injection molding machine. It is observed that melt behind from the sleeve will flow through the core of melt ahead and lead the melt front. Fountain flow in high speed micro-injection molding is dominant. During penetration, the colored melt, which is behind the transparent melt originally, is comparatively hot and flows along the core, following the inner side of core to seek shortest flow path.
Preparing of Homogeneous Solution of Ultrahigh Molecular Weight PAN
Authors: Zhang B. , Zhao J. , Zhang Y. , Yang N. , Wu C.
Published: December 2013

Based on torque measurement via a device specially developed by our group, the shearing torque of the mixture of UHMWPAN with swelling agent or solvent during shearing process at various temperatures could be recorded as torque-temperature diagram in the swelling and dissolution process. The temperature where the torque of the mixture began to rise as showed in the torque-temperature diagram was considered as key parameter. UHMWPAN could be swollen fully and the homogeneous solution could be easily prepared if the mixture was heated progressively and was kept for a certain period of time at the every constant temperature. In the case of UHMWPAN (content ≥ 5 %), the parameters of the swelling and dissolution process were finally obtained.
High-speed Melt Spinning of Polyethylene terephthalate with Periodic Oscillation of Take-up Velocity
Authors: Takarada W. , Kazama K. , Ito H. , Kikutani T.
Published: December 2013

To investigate the non-steady-state melt spinning behavior, take-up velocity was varied periodically in the high-speed melt spinning process of polyethylene terephthalate and the time-course changes of velocity and diameter of the spin-line were measured simultaneously. A numerical simulation program for the non-steady-state melt spinning process was also developed. In the range of relatively low take-up velocities, experimental results and results of numerical simulation of the non-steady-state melt spinning process showed a fair agreement, in that the amplitude for the variation of the reciprocal of the cross-sectional area and that for the variation of velocity of the spin-line had a linear relation. An increase in the frequency of velocity oscillation led to a less significant variation in the thickness of as-spun fibers. On the other hand, there was a phase shift between the oscillation of take-up velocity and that of the reciprocal of cross-sectional area of the spin-line at the point of take-up. When take-up velocity was increased, starting of the orientation-induced crystallization along with the occurrence of neck-like deformation caused some characteristic behaviors such as significant increases in the amplitudes of velocity and diameter fluctuations at a certain region in the spin-line. Such behaviors could be reproduced in the numerical calculation by incorporating the stress dependent change of solidification temperature. It was also revealed that the orientation-induced crystallization has the effect of stabilizing the spinning system.
Drawability of As-spun PP Fibres
Authors: Yang R. D. , Mather R. R. , Fotheringham A. F.
Published: December 2013

The drawability of as-spun polypropylene (PP) filaments was studied using a statistical approach including an experimental design and statistical analysis. The use of a statistical experimental design allows all possible interactions as well as main factors to be evaluated. As a result, one two-factor interaction (between winding speed and metering pump speed, WS*MPS) and two main factors (winding speed WS and metering pump speed MPS) were identified as factors having statistical significance on drawability of as-spun PP filaments with risk levels (P values) less than 0.005. The drawability can be improved by controlling the structure of the as-spun filaments, that is a paracrystalline structure combined with a very low overall orientation (birefringence <3.2 × 10–3). Application of two-stage drawing also increases the drawability compared with one-stage drawing.
In-process Monitoring of Micromoulding – Assessment of Process Variation
Authors: Whiteside B. R. , Martyn M. T. , Coates P. D.
Published: December 2013

Advances in micromoulding technology are leading to complex, net-shape products having sub-milligramme masses with micro-scale surface features in a range of polymer and nanocomposite materials. For such small components subjected to the extreme stress, strain-rate and temperature gradients encountered in the micromoulding process, detailed process monitoring is desirable to highlight variations in moulding conditions and assist in creating a viable manufacturing process with acceptable quality products. This paper covers the implementation of a suite of sensors on a commercial micromoulding machine and detailed computer monitoring during processing of a polyacetal component over a range of processing conditions. The results determined that cavity pressure curve integral data provides the most sensitive factor for characterisation of a moulding process of a 0.34 mm3 (0.49 mg) product. The repeatability of the process is directly compared with that of a 15.6 mm3 (22.2 mg) product and shown to be inferior. DSC measurements of the whole products indicated little variation in average crystallinity of the products manufactured over a mould temperature range of 30 to 130 °C.
Evolution of Morphology of iPP in Processing Conditions
Authors: Coccorullo I. , Pantani R. , Titomanlio G.
Published: December 2013

A model for crystallization kinetics that accounts for the formation of different crystalline phases and is able to describe the morphological characteristics of samples solidified under quiescent conditions, has been enriched to account for the effect of solidification pressure. The effect of pressure was considered by assuming a linear increase of melting and glass transition temperatures (which are involved in the description of the growth rate and nucleation density of the alpha phase). Moreover, pressure was incorporated in the kinetic constant adopted to describe the evolution of the mesomorphic phase. The parameters of the model were identified on the basis of literature data on the distribution of crystalline phases in samples solidified under different pressures. The modified model also satisfactorily described PVT curves up to 100 MPa, and is now able to describe the evolution of morphology during solidification at cooling rates as fast as several hundreds of Kelvin degrees per second and under pressures of as high as 100 MPa.
Stretch and Shape Distributions of Droplets with Interfacial Tension in Chaotic Mixing
Authors: Pham T. N. , Tucker C. L.
Published: December 2013

A numerical simulation is developed to study the time-dependent shapes of droplets in chaotic mixing, as a function of interfacial tension and droplet-to-matrix viscosity ratio. The two-dimensional, time-periodic Newtonian flow between eccentric cylinders is used as a prototype mixing flow. The microstructure is modeled as three-dimensional ellipsoidal droplets, ignoring breakup and coalescence. A Lagrangian particle method is used to follow the microstructure. When interfacial tension is small (global capillary number is large), the major axes of the droplets exhibit the same stretching statistics as passive fluid elements and droplets with zero interfacial tension in chaotic flows: the geometric average of the stretch ratio grows exponentially with time, at a rate equal to the Lyapunov exponent of the flow, while the log of the major-axis stretch of the droplets, when scaled by its instantaneous mean and standard deviation, has a time-invariant, Gaussian global distribution and a non-uniform, fractal, and time-invariant spatial distribution. In this regime the stretch of the longest droplet axis is insensitive to interfacial tension, but the shape of the cross section is very sensitive: initially spherical droplets deform first into ribbons or sheets, but eventually transform into axisymmetric threads. The larger the global capillary number, the longer the sheet morphology persists, but sheet-like structures are always transient, and the sheets relax to threads if mixing goes on too long.
Advanced Finite Element 3D Injection Molding
Authors: Silva L. , Gruau C. , Agassant J.-F. , Coupez T. , Mauffrey J.
Published: December 2013

In this paper, we present aspects and examples relating to Rem3D, a 3D finite element software dedicated to the computation of the entire injection molding cycle (filling, packing and cooling). Recent developments are presented, namely mesh generation and adaptation driven by a local natural metric, compressible Stokes and temperature solvers, as well as a multidomain approach. As an example of the application of Rem3D, computations have been compared with well instrumented experiments for a complex mold geometry.
On PVT and Rheological Measurements of Polymer Melts
Authors: Sedlacek T. , Cermak R. , Hausnerova B. , Zatloukal M. , Boldizar A. , Saha P.
Published: December 2013

The relation between PVT and rheological measurements of several polymer melts including polyethylenes, polypropylene, polystyrene, poly(methyl methacrylate), and polycarbonate has been taken into investigation. Pressure-temperature dependent viscosities, determined on rotational and backpressure-modified capillary rheometers, were fitted through the Carreau-Yasuda model. PVT data was analyzed by the help of the Simha-Somcynsky equation of state (SS EOS). The thermodynamical parameters of the SS EOS were connected to constant-stress viscosity (experimental) and zero-shear viscosity (extrapolated). The Doolittle relationship was modified into the form of

η
 
=
 
exp

(

C
1

 
ln

(

h
′

h

)

)

. The relation was employed and tested for the data evaluation. It proved to be a good tool for linearization of PVT and rheological data.
External Calibration in PA12 Tube Extrusion
Authors: Carin A. , Haudin J.-M. , Vincent M. , Monasse B. , Bellet G. , Silagy D.
Published: December 2013

In PA12 tube extrusion, calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two calibration conditions have been carried out to validate our work. Three main calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the calibration tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the calibration tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during calibration. We showed quantitatively that rising the water layer thickness leads to a diminution of the draw ratio in the calibration tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main calibration parameters to improve lubrication and restrict draw ratio in the calibration tank.
Crystallinity and Linear Rheological Properties of Polymers
Authors: Lamberti G. , Peters G. W. M. , Titomanlio G.
Published: December 2013

The crystallization of a polymer melt, taking place during transformation processes, has a great impact on the process itself, mainly because it causes a large increase in the viscosity (hardening). Knowledge of the hardening kinetics is important for modeling and controlling the transformation processes. In this work, first an overview is given of the experimental and modeling work on the hardening of crystallizing polymers. Next, we present isothermal crystallization experiments using differential scanning calorimetry (DSC) and rotational rheometry to measure the dynamic viscosity. The evolution of the relative crystallinity and normalized complex viscosity are correlated by a novel technique which allows simultaneous analysis of several runs, even if they are not carried out at same temperatures; the main requirement with the traditional technique. The technique, described in detail in this paper, provides an experimental relationship between the crystallinity and the hardening, i.e. the increase in the viscosity. Moreover, by measuring the dynamic viscosity at different frequencies, surprisingly, a master curve is obtained which combines the effects of shear rate, temperature and the level of crystallinity.
Experimental and Theoretical Approach to the Extrusion of Rubber Compounds with a Two-Stage Screw**
Authors: Vergnes B. , Bennani N. , Guichard C.
Published: December 2013

The extrusion of EPDM compounds with a two-stage vented screw has been studied. Experimentally, the pressures and temperatures were measured at the end of each stage, for different processing conditions (screw speed, die geometry etc.). Screw pulling experiments have allowed to observe the partially filling of the different screw sections. Assuming a power-law pseudoplastic behaviour for the rubber compound, the flow in each stage of the screw has been computed. The evolutions of the pressure and the temperature all along the screw, as well as the filling length of the second stage are then obtained. The theoretical results are in good agreement with the experimental measurements.
Polymer Compounding Process for Controlled Peroxide-Degradation of PP
Authors: Fritz H.-G. , Stöhrer B.
Published: December 2013

A process control concept for peroxide-initiated degradation of polypropylene was presented. The link-up of a twin-screw extruder to an on-line Rheometer and a computer system using a newly developed program package can he used to form a process control system unaffected by external disturbing influences and leading to a long-term constant product quality. Work is still to be done concerning development and optimization in the area of layout and design of adapter systems and concerning the measures for lowering the controllability ratio Z1 Special attention should be given to a processing concept to enable changes in M̅w and MWD independently of one another.
Injection Molding of Reinforced Thermosets
Authors: Blanc R. , Philipon S. , Vincent M. , Agassant J.F. , Alglave H. , Müller R. , Froelich D.
Published: December 2013

The orientation of glass fibers (initial length 20 mm) and the mold filling of reinforced unsaturated polyester compounds have been studied. Observations of the fiber orientation have been made in three molds where shear and elongational flows occur in variable ways. A part of the fibers are split and broken into filaments. Reinforcement can be more or less buckled. A thin skin layer without fibers is observed. The great thickness of a core region with an orientation perpendicular to the flow direction shows the importance of negative elongational flows. Efficiency of positive elongational flows to suppress buckling and to give a well flow aligned orientation is also observed. On the contrary the efficiency of shear flows is limited compared to elongational flows. The incidence of injection conditions on the pressure inside a rectangular plaque has been studied both experimentally and theoretically. Experimental difficulties due to the material heterogeneity leads to measure viscosity data of the uncured material on a special capillary rheometer and rheological kinetic data on a simplified compound. Numerical results are in good agreement with experimental measurements. For instance the effect of crosslinking which leads to a pressure rise at low flow rate or high mold temperature is well predicted.
Gel-Permeation Chromatography as a Tool for the Real-Time-Estimation of the Chain length Distribution in a Polymerization Reactor
Authors: Papadopoulou S.
Published: December 2013

The knowledge of the chain length distribution (CLD) during the operation in a polymerization reactor is necessary in order to control polymer quality. Model-based measurement methods (Kalman filter) provide the possibility of reconstructing on-line not directly accessible process states from easily available measurements. However, the presence of model inaccuracies or disturbances influencing primarily the CLD demand additional measurement information about CLD.

An extended Kalman filter composed of two decoupled filters and considering Gel-Permeation chromatographic, (GPC), measurements for the continuous estimation of the CLD in the case of free radical polymerization of styrene is discussed. Although the existence of a time delay, due to the GPC analysis, the consideration of this measurement in the filter algorithm produces the local observability of the states characterizing the CLD, allows continuous access to the CLD and its characteristic values and provides a periodical adaption of the CLD to the reality.
Flow Visualization Parallel and Perpendicular to the Rotor Axes for Elastomers and Molten Plastics in an Internal Mixer
Authors: Min K.
Published: December 2013

Basic studies of flow visualization for elastomers and plastics in an internal mixer are described. A modified laboratory mixer with transparent front and trasverse windows was used to observe parallel and perpendicular motions. Shearing, stretching and tearing motions were observed especially for elastomers. Various rotor designs were used. These indicate different flow fields along the rotor axes, and the interchange of materials between rotors. We describe the different flow fields observed for elastomers and plastics creasted by various rotor designs.
Recent Studies on Degradation Mechanism of Rubber Vulcanizates by Chemorheology
Authors: Murakami K.
Published: December 2013

A critical discussion is presented of the influence of chemical degradation mechanisms on the mechanical properties, especially stress relaxation, of vulcanized rubber. The response of the vulcanizate is interpreted in terms of the kinetic theory of rubber elasticity. Different chemical mechanisms are explored. The influence of diluent is interpreted in terms of the kinetic theory of rubber elasticity. Different chemical mechanisms are explored. The influence of diluent is considered. Comparisons are made to experiments on polyisoprenes and polyurethanes.
On Dispersed Crystallization in Polymer Melts as Proceeding from a Quenched Boundary
Authors: Janeschitz-Kriegl H. , Krobath G.
Published: December 2013

The present paper is concerned with a crystallization process which occurs in the interior of a polymer melt, when its boundary (mold wall etc.) is suddenly quenched. As polymer melts are prone to supercooling, dispersed nucleation can take place at a distance from the boundary, if the local temperature has become low enough. This results in (delayed) formation of a crystallization zone moving into the bulk of the material. An approximate methematical treatment of this phenomenon enables an easy (semi-quantitative) interpretation of experimental results which were obtained with the aid of a technique of visual inspection on a high density polyethylene (HDPE) sample.
Simulation of Flow and Mixing in an Internal Mixer
Authors: Kim J. K. , White J. L. , Min K. , Szydlowski W.
Published: December 2013

A mathematical model is developed for simulation of flow in an internal mixer with two counter rotating non-intermeshing rotors is presented. The model presumes rotors with a screw flight which is separated into two sections. The mixing chamber is taken to be fully filled and rotor curvature neglected in analogy to screw extruder analyses. Lubrication theory is used and the fluid presumed Newtonian. The flow patterns within the mixing chamber are computed. The conditions under which rotor designs lead to global circulation patterns within the mixing chamber and good distributive mixing are considered. We also investigated the extent of fluid motion over rotor tips which should lead to dispersive mixing.
Gelation and Fusion of PVC Plastisols with Plasticizers of Varying Solvent Power
Authors: Nakajima N. , Sadeghi M. R.
Published: December 2013

During gelation and fusion process PVC plastisols changes from a suspension of resin particles in a liquid plasticizer to a uniform mass. The manner of change was observed with a scanning electron microscope, SEM. Four different plasticizers varying solvent power were used: they were dioctyl phthalate, dioctyl sebacate, dibutyl sebacate and tricresyl phosphate. Significant differences were observed among different plasticizer systems in a manner of dissolution of PVC into a plasticizer, swelling of PVC particles with a plasticizer and fusing to form a uniform mass. The SEM micrographs are presented with reference to the viscoelastic properties at the corresponding temperature.
Thermal Aging on the Dielectric Properties of Recycled High Impact Polystyrene
Authors: Salman S. R. , Al-Jarrah M. F. , Hammo S. A.
Published: December 2013

The dissipation factor and dielectric constant of thermally aged recycled high impact polystyrene (HIPS) were measured at different aging temperatures. The results indicates that the degradation of HIPS is mainly due to surface action with minor chemical change.
Structure Development in the Melt Spinning and Drawing of Poly p Phenylene Sulfide Fibers
Authors: Song S. S. , White J. L. , Cakmak M.
Published: December 2013

The development of crystallinity and orientation in melt spun and subsequently drawn poly p phenylene sulfide (PPS) fibers is investigated using differential scanning calorimetry (DSC), birefringence and wide angle x-ray diffraction (WAXS) techniques. The melt spun PPS fibers were found to possess small amounts of crystallinity at moderate draw-down ratios. The fibers may be crystallized to a significant extent by subsequent drawing over a hot plate. The levels of crystallinity and orientation in the largely glassy melt spun PPS fibers has been determined as well as subsequently drawn fibers. Uniaxial mechanical properties were determined as a function of spinning and drawing conditions. In general, elongation to break decreases while modulus and tensile strength increase with an increase of melt spinning draw down ratio and solid draw ratio. The Young's modulus and tensile strengths are increasing functions of fiber birefringence and the elongation to break a decreasing function.
Air Ring Effect on Blown Film Dynamics
Authors: Cao B. , Campbell G. A.
Published: December 2013

The air ring has an effect on blown film dynamics. By using a momentum macrobalance, an analytical solution for the pressure on the outer surface of the bubble is obtained which is in fairly good agreement with our aerodynamic experimental data. Since the pressure is related to the hoop stress, a more complete prediction of the bubble shape is attained by taking the air ring effect into account.
Advances in Rheological Analysis of Injection Molding
Authors: Bernhardt E. C. , Bertacchi G. , Moroni A.
Published: December 2013

Finite element methods offer the potential to greatly refine mold filling analysis. As a consequence, there is strong pressure to apply this technology on a routine basis in industry. Unfortunately, traditional finite element techniques are not adequate to design a viable model of the flow of molten plastic into a mold. This paper explains the mathematical problems that must be solved. It describes why the widely used classical matrix techniques give erratic results, and demonstrates that it is mandatory to apply a total dynamic analysis to obtain a reliable mold filling simulation. A new technique is introduced to solve the problems caused by non-linear material properties and moving boundaries.
Position of Neutral Surface during Hollow Disk Compression Molding of Long Fibre-Reinforced Thermoplastics**
Authors: Hojo H. , Kim E. G. , Onodera T. , Yaguchi H. , Kim S. H. , Koshimoto M.
Published: December 2013

A model is presented which can be used to explain the friction condition on the interface between the composites and the mold during sheet-like parts compression molding of fibre-reinforced thermoplastics. The composites is treated as an incompressible isotropic fluid. Circular hollow disk is compressed in order to derive the position of the neutral surface which can explain the interfacial friction from consideration of minimum energy dissipation. From the theory and the experiment, it is clear that there is slip on the mold surface. By using the nondimensional parameter which measures the ratio ofvicous to frictional resistance, the phenomenon of the friction can be well explained.
A Model for Single-screw Plasticating Extruders
Authors: Vincelette A. R. , Guerrero C. S. , Carreau P. J. , Lafleur P. G.
Published: December 2013

A mathematical model has been developed to describe the steady-state behavior of single-screw plasticating extruders. The model is capable of predicting the solid bed profile, pressure, and polymer temperature profiles along the screw channel. The model is based on concepts developed by Tadmor and Klein [1], but a modified model for plastication rate is proposed and the pressure profile is calculated using a unidirectional power-law flow model, in which correction factors for flight walls, curvature, and varying channel height have been incorporated. A finite difference technique (Crank-Nichols on method) is used to compute the polymer temperature profile. The overall extruder performance (pressure, temperature and solid bed profiles) is obtained with short computer times on a personal computer (typically one minute on IBM AT). A series of menus and graphics allow for selective simulation and rapid visualization of effects of key parameters, making the model attractive for screw design and optimization of operating conditions. The predictions are in good agreement with experimental data obtained for a polyethylene on a 45 mm diameter screw extruder.
Flow in a Modular Intermeshing Co-rotating Twin Screw Extruder
Authors: Wang Y. , White J. L. , Szydlowski W.
Published: December 2013

The flow of viscous power law fluids in the various modules of a modular intermeshing co-rotating twin screw extruder. This includes right-handed and left-handed screw elements and kneading disc assemblies with various staggering angles. The calculations are based on hydrodynamic lubrication theory used a new calculation method based on combining methods by Tadmor, Broyer and Gutfinger, and by Griffith. The behavior of a composite twin screw extruder consisting of assemblies of screw and kneading disc elements is investigated and the potential of having a sequence of fully filled and starved regions is considered. The existence of such distribution of polymer and starvation behavior in a twin screw machine was found in experiments with a polyethylene. The material distribution is reasonably well predicted by the non-Newtonian flow model of this paper.
Incremental Drawing of Polyethylene-terephthalate Partially Oriented Yarn (PET-POY)**
Authors: Mukhopadhyay A. K. , Misra A. , Dutta B.
Published: December 2013

Polyethylene terephthalate (PET) is generally melt spun to give yarns which are then drawn at an elevated temperature since the glass transition (Tg) of PET is 70 °C. Incremental drawing of synthetic fibers involves the drawing of as-spun yarns in several discrete steps along the surface of two corotating conical bodies. For drawing at an elevated temperature a chamber type of heating system was designed in which the drawing bodies were enclosed and a constant temperature maintained. Multifilament PET-POY (Polyethylene Terephthalate-partially oriented yarn) of 130 denier/34 filaments was drawn at 300 m/min with the draw-ratios of 1.76, 1.84 and 2.00 respectively by incremental drawing process (IDP) as well as by the conventional drawing process (CDP) and the properties compared. It was seen that the mechanical and structural properties were significantly better in case of IDP than CDP at equivalent draw-ratios. The mechanical property results are explained on the basis of structural development during drawing.
Drawing Behavior of Solution Modified Polyethylene
Authors: Malik T. M. , Carreau P. J. , Schreiber H. P. , Rudin A. , Tchir W.
Published: December 2013

The relationship between draw ability of high density polyethylene (HDPE) and entanglement density in the polymer has been studied by solution modifying the polymer. This involved precipitating the polyethylene from solutions in trichlorobenzene. Entanglement densities of solution modified and control (as received) HDPE were estimated from low-shear melt viscosity data. One and two stage drawing techniques at closely controlled temperatures were applied to form drawn film specimens. It was shown that solution modified versions of HDPE permitted drawing to much higher ratios than the control, and resulted in films with elastic moduli in the 40 GPa range. A relationship is thereby suggested linking polymer entanglement density with mechanical properties attained in the drawing process. Optimization of drawing performance appears to be attainable by controlling entanglement density, through appropriate choices of solvent and of initial polymer concentration in the solutions.
Flow Field Characterization in a Banbury Mixer
Authors: Cheng J. J. , Manas-Zloczower I.
Published: December 2013

A fluid dynamics analysis package – FIDAP using the finite element method was implemented to simulate the flow patterns in a Banbury mixer. A number of different geometries were selected to represent the dynamic motion of the rotors during a repeated mixing cycle. The simulation results were then used to characterize the flow field in terms of a parameter quantifying the elongational flow components. The influence of design and processing variables on the flow characteristics as well as on the average shear rate were analyzed.
Deformation Fields and Residence Time Distributions in Polymer Melt Flows
Authors: Hannachi A. , Mitsoulis E.
Published: December 2013

In past numerical simulations of polymer melt flows, the flow field has been visualized through velocity vectors and streamlines providing a steady-state Eulerian viewpoint. This work shows that enhanced understanding of flow kinematics can be achieved by calculating the residence time distribution (RTD) of material points through the integration of the known velocity field and by plotting isochrones and the deformation field of fluid elements. Such kinematic patterns provide a Lagrangian viewpoint of the flow and fully describe the history of the elements of the system as they move through the field. In cases with zones of recirculation the period for one revolution is also calculated. Typical examples are shown for such polmyer processing operations as entry flows in contractions, exit flows from dies, calendering and wire-coating coextrusion processes.
Flow History – Morphology Development in Crystallizable Polymer Melts
Authors: McHugh A. J. , Khomami B.
Published: December 2013

Flow history-morphology interactions have been studied for three crystallizable polymers: high density polyethylene, poly(vinylidene fluoride), and polypropylene. Materials were extruded through an impinging channels film die which produces a mixed extensional and shearing flow field. Extrudate morphology was characterized by optical microscopy and x-ray diffraction. Stress fields during die flow were measured from flow birefringence and compared to calculations based on the power law model. Good quantitative agreement was found for the shearing stresses, however, large differences were observed between the measured and computed normal stresses along the symmetry axis of the flow where extensional gradients are also the highest. Extensional stresses on the order of 2.8·106, 1.4·106, and 3.9·105 dynes/cm2 were required to induce row-nucleated crystallization in the HDPE, PVF2, and polypropylene respectively. The respective stresses were found to decrease with increasing relaxation time in a non-linear fashion. An explanation for this behavior is presented based on the opposing tendencies of chain relaxation and oriented crystallization.
Rheological Studies on Solutions of Poly-p-phenylene Terephthalamide in H2SO4
Authors: Xu Y. , Qian R.
Published: December 2013

The material functions, viscosity η, the first normal stress function N1, dynamic shear moduli G′ & G″ from sinusoidal oscillatory measurements and the transient responses of stress build up and stress decay in step flow were investigated experimentally for solutions of poly-p-phenylene terephthalamide in H2SO4 at concentrations from 0.5 to 10 wt.-% covering the phase transition from isotropic to nematic LCP solutions at 8 % where all mentioned properties change abruptly. General analytical forms have been found for η and η* functions. LCP solutions show high value of N1 which builds up at shear strain larger than the yield value of 2. The structural origin for the observed rheological properties are discussed.
Spreader Blade Analogy of Flow Past an Internal Mixer Rotor
Authors: Nassehi V. , Freakley P. K.
Published: December 2013

This paper deals with the finite element modelling of non-isothermal flow of a power-law fluid past an internal mixer rotor. The model uses a set of boundary constraints which correspond to stressfree surfaces at the inlet and the outlet of the domain. At the walls of the domain the conditions of no-slip, controiled-slip and perfect-slip are alternatively incorporated in the simulations. A stream-line upwinding technique used in the solution scheme enables it to yield convergent results for high Peclet No. flow, even if relatively coarse meshes are used. Comparison of these results with the available experimental evidence confirm the general validity of the methods used.
Non-Newtonian and Non-Isothermal Modeling of 3D-Flow in an Internal Mixer
Authors: Kim J. K. , White J. L.
Published: December 2013

In previous work we have applied hydrodynamic lubrication theory to simulate 3-dimensional flow of a polymer melt or elastomer in an internal mixer. That study presumed isothermal Newtonian flow in a flattened out mixing chamber. In the present paper, we take into consideration both non-Newtonian flow properties of the melt/elastomers and increase in temperature due to viscous dissipation heating. We consider the influence of non-Newtonian viscosity on flow patterns in the internal mixer. Viscous dissipation heating in the internal mixer is also modelled. It is shown that large scale internal mixers tend to operate adiabatically while small scale machines are close to isothermal. Temperature-time profiles are predicted for laboratory and large scale internal mixers.