bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.