bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long Glass Fibre Reinforcement of Thermo Plastics
Authors: Bush S. F. 
Published: December 2013

Abstract
The paper summarises the main experimental and theoretical results from a long-term programme of research (SAFIRE) to produce and apply long glass fibre compounds to the extrusion of pipes, sheets and profiles and to injection, blow and roto moulding. The overall objective is to obtain the processing speeds associated with short fibre reinforced thermoplastics with the reinforcement efficiencies associated with prepositioned or prepreg thermoset composites. Extrusion and injection moulding are now in the commercial domain, with industrial scale trials underway in the other technologies.
Long glass fibres are defined by their ability to form lace-like mat structures within the polymer melt which persist into the solid state. Such structures, which greatly increase both melt strength and solid state thermo mechanical properties, can be formed with fibre volume concentrations (c) as low as .01. The formation of mat structures depends on the number N of virtual touches per filament. A minimum of around five touches is generally needed. From earlier work N is given as A.c. l/d. A varies with mean fibre orientation in the mat: for the random in-plane case it is approximately 8/π2, so that in contrast with typical fibre suspensions (c < d/l) extremely strong particle-particle interactions are involved in the melt state.
In the solid state, tensile strength is measured and modelled in terms of number average fibre length (l) and diameter (d), polymer yield strength, fibre distribution efficiency, interfacial shear strength and a specially defined matrix stress magnification factor M. The role of patented fibre management devices in optimising these variables as they appear in the solid state is defined and described.
Mixing Homologous High Viscosity Ratio Polymer Blends in Converging Flow
Authors: Meller M. , Luciani A. , Månson J.-A. E. 
Published: December 2013

Abstract
Several studies have shown that deformation and breakup of dispersed droplets is easier in extensional than in shear flow field and this is particularly true for systems with high viscosity ratios. The simplest way to generate a significant extensional flow field in compounding equipment is to use converging flow conditions. In this work, the mixing efficiency of converging flow has been investigated as a function of the entry profile and the flow rate by using a capillary rheometer equipped with dies of different geometries. The material used for this study was a bimodal polyethylene presenting inhomo-geneities due to the high viscosity ratio between the low and high molecular weight fractions. The results indicated that the mixing performance depended strongly on the die geometry and flow rate. A critical flow rate was observed for each particular entry profile at which the highest efficiency was observed. This critical flow rate was found to correspond to the onset of melt flow instabilities.
Numerical Simulation of the Film Casting Process
Authors: Beaulne M. , Mitsoulis E. 
Published: December 2013

Abstract
Numerical simulations have been undertaken for the film-casting process with viscoelastic fluids. Viscoelasticity is described by an integral constitutive equation of the K-BKZ type with a spectrum of relaxation times, which fits well experimental data for shear and extensional viscosities and the normal stresses measured in shear flow. Non-isothermal conditions are considered by applying the Morland-Lee hypothesis, which incorporates the appropriate shift factor and pseudo-time into the constitutive equation. A one-dimensional model derived from the conservation of momentum is used to approximate the thickness, while the stress free-surface condition is used to approximate the width. The resulting system of differential equations is solved using the finite element method and the Newton-Raphson iterative scheme. The method of solution was first checked against the Newtonian and Maxwell results for different film geometries. The simulations are compared to available experimental data and previous simulations in terms of film thickness, film width, and film temperature. Agreement between the experiments and the current simulations is considered good with subtle differences. Agreement is also considered good between the current one-dimensional simulations and previous two-dimensional simulations for viscoelastic fluids, in terms of width and thickness. The one-dimensional model is advantageous since the algorithm is relatively simple, convergence is almost guaranteed, and the computing time is short.
Tensile Force Measurements in the PA 6 High Speed Fiber Spinning and their Utility
Authors: Beyreuther R. , Brünig H. , Hoftmann H. 
Published: December 2013

Abstract
The paper deals with practical and theoretical investigations of the PA 6 high speed fiber spinning process in the velocity range from 3000 until 5450m/min by means of tensile force measurements in the spinning line below the fiber solidification point. The measurements were evaluated under three different goals as follows:

Quantitative determination and interpretation of relations between the technological and textile-physical fiber parameters spinning speed, throughput, and fiber fineness (in the range of 4.1 to 14.8 dtex for a single filament spun from a 9-holes die).

Comparison between the experimentally measured and the theoretically calculated tensile forces by means of the own fiber formation model developed in the last years. On this occasion a satisfactory concordance could be noticed between the experimental and theoretical results. In addition to this a good model parameter estimation could be proved in the force balance part of the differential equation system for the fiber formation.

Spectral analytical evaluations of the measured tensile force time functions by means of their autocorrelation functions. It could be demonstrated, that higher frequency tensile force disturbances could be caused both by the spinningpump and by unevennesses in the cross quench air conditions below the spinning die.

All results from the investigations above are discussed in relation to different technological process goals and their realization possibilities.
Effect of Wall Slip on Rheotens Mastercurves for Linear PE Melts
Authors: Bernnat A. , Wagner M. H. 
Published: December 2013

Abstract
For two linear polyethylene melts, a HDPE and a LLDPE, Rheotens experiments at constant extrusion pressure and different extusion temperatures are reported. While at sufficiently small extrusion pressure Rheotens mastercurves were found, various deviations from the mastercurves were observed at higher extrusion pressures. By use of capillary rheometry and Mooney's method, these deviations could be attributed to a stick-slip transition in the extrusion die, and, in the case of LLDPE, to partial wall slip below the stick-slip transition.
Residual Stresses and Birefringence in Injection Molding of Semicrystalline Polymer
Authors: Guo X. , Isayev A.I. 
Published: December 2013

Abstract
A composite model for the buildup and the relaxation of residual stresses and birefringence during the injection molding of semicrystalline polymer is proposed. This model takes into account the flow-induced crystallization occurring under nonisothermal conditions. The effects of crystallization on the variations of mechanical and physical properties are considered. The viscoelastic constitutive equation due to Giesekus and Leonov is employed for the calculation of the buildup and relaxation of flow stresses, whereas the Morland-Lee constitutive equation of linear viscoelasticity is utilized for the calculation of the buildup and relaxation of thermal stresses during the molding. The overall residual stresses in the molding are determined based upon the addition of residual flow and thermal stresses. The multilayered micro-structure in the moldings arising due to the flow-induced crystallization is determined. Flow birefringence is related to flow stresses according to the stress-optical rule. An expression is proposed to evaluate the overall residual birefringence based upon the resultant microstructure pattern and residual low birefringence in the moldings. As a result, numerical simulations for idealized injection molding process are formulated to calculate the residual stresses and birefringence in molded semicrystalline polymers. Based upon the above theoretical approach, the numerical simulation schemes are formulated, and a computer program is developed. Based upon the simulations, the effects of molding conditions and molecular weights on the overall residual stresses and birefringence are further evaluated.
Evaluation of the Thermal Behaviour of Injection Moulds
Authors: Barros I. , Teixeira S. F. C. F. , Teixeira J. C. , Cunha A. M. 
Published: December 2013

Abstract
It is well known that the thermal behaviour of moulds used for thermoplastics processing has an important effect on both the part quality and the process productivity. The present work reports a study on the evaluation of the relative effect of different geometric and operational parameters on the thermal behaviour of injection moulds. It uses a mathematical model developed to simulate the thermal transient exchanged during the entire moulding cycle. The model is based on a 2D Fourier equation, uses an adaptive grid and describes the thermal contact resistance at mould/polymer interface. The cooling time and the interface temperature distribution are calculated from the computed temperature field in the domain under study. Experimental data, obtained with an instrumented tool during typical production conditions, is used to validate the developed model. The evaluation analysis is based on the Taguchi methodology used to rank the relative effect of the parameters on the selected variables (cooling time, temperature distribution and number of cycles to reach the thermal steady state).
Rheological and Morphological Properties of Immiscible Blends and Microfiber Preparation from the Blends
Authors: Lyoo W.S. , Choi Y.G. , Choi J.H. , Ha W.S. , Kim B.C. 
Published: December 2013

Abstract
One modified poly(ethylene terephthalate) (m-PET) containing 16 mol% of isophthalic acid content and three kinds of isotactic polypropylene (i-PP) with different molecular weights were melt blended in various volume ratios by a twin screw extruder. The dynamic viscosity of the i-PP/m-PET blend showed positive deviation at lower volume content of i-PP and negative deviation at higher volume content of i-PP. The size of dispersed phase increased with an increase of the minor component. Also, the less difference between the viscosities of two polymers caused the smaller particle size in the blend and the smaller critical Weber number. After melt spinning of these binary polymer blends, m-PET and i-PP micro staple fiber, whose diameter was about 0.13 to 2.75 μm, could be obtained by extracting the continuous phase with a proper solvent. The less the minor component in the blend, the better the spinnability of the blended polymers and the physical properties of the fiber. Also, when i-PP was the continuous phase, the spinnability and the physical properties of the fibers were better than the opposite case. Molecular weight of i-PP and the blend ratio had a marked influence on the diameter of microfibers. The micro fiber obtained from i-PP which has similar viscosity with m-PET showed the smallest diameter than those obtained from other two i-PPs.
Filling and Postfilling Analysis of Injection/Compression Molding
Authors: Young W.-B. 
Published: December 2013

Abstract
Injection compression molding is a process that modifies the original injection molding process to have a compression stage after the injection. This process is suitable for precision injection molding parts. The success of an injection compression molding process relies on proper design of the mold and selection of process conditions. The main scope of this study is to develop a process simulation tool for the injection compression molding process. The simulation tool is used to predict the state variations of the material during the molding, including molding flow, distributions of temperature and pressure, and the material shrinkage. The effect of the compression action on the molding part as investigated by this study. The compression action can provide more uniform packing on the mold cavity. But, with the non uniform cooling, material can have different fluidity in the cavity, which induces pressure gradients during the compression action. From the simulation results, it is demonstrated that a two stage compression action in the injection compression molding process can reduce the pressure gradient in the cavity and still have lo shrinkage. By using this method, products ith higher precision and lower warpage can be molded.
A Transient Melting Model of Polymer Balls Sliding Against the Barrel
Authors: Yung K. L. , Xu Y. , Lau K. H. 
Published: December 2013

Abstract
In the study of solid conveying process in plastics screw extrusion, a particle element numerical method enables us to simulate behavior of each solid particle during the process and takes into consideration the parameters of individual particle in the calculation.
The melting of pellets in the solid conveying section is caused predominantly by heat from both friction and conduction through close contact. Experiments showed, melting happened before the solid plug was formed. Hence, when a particle element numerical method is used to simulate the conveying and melting process in the injection bellow, the analysis of melting process caused by solid particles sliding against wall of bellow should be included. Searching through the recent literature, no valid analysis of the transient close-contact melting process caused by viscous dissipation was found. This paper attempts to present an analysis of the melting process and derive an expression for describing the transient melting caused by both friction and close-contact heating. The melting model of polymer pellets sliding against the barrel was achieved by assuming the friction against the barrel as friction against an isothermal wall given the high heat conductivity of the barrel. To keep the expression simple, a constant temperature boundary condition is utilized for the wall which concurs with reality.
The Mapping Method for Mixing Optimization
Authors: Kruijt P. G. M. , Galaktionov O. S. , Peters G. W. M. , Meijer H. E. H. 
Published: December 2013

Abstract
The application of the mapping method [1, 2] on fully three dimensional flows with dynamic boundaries is presented. The computational domain is a (three dimensional) section of a particular type of screw element in a closely intermeshing corotating twin screw extruder. Screw elements include transport, different kneading, and counterconveying zones, for each of which a mapping matrix has to be constructed.
In the future, different screw assemblies could be studied by combining distinct mapping matrices, much like an actual screw is assembled from distinct modules. In this paper, the principle and applicability of the mapping method is demonstrated by the analysis of a fully filled transporting section of the corotating twin screw extruder. Concentration and residence time distributions can be computed straightforwardly and the volume average intensity of segregation is chosen as a characteristic mixing measure to quantitatively describe distributive mixing.
Impregnation Behaviors in Composite Processing
Authors: Matsuo T. , Yuba T. , Kawabe K. 
Published: December 2013

Abstract
In the first part of this paper, impregnation was positioned in terms of consolidation in composite processing and theoretical model for impregnation behaviors was presented. Impregnation behaviors were classified using the parameters contained in the model. Calculation for some simple cases was conducted. In the second part, impregnation behaviors of two material groups were experimentally estimated by on-line measurement of tool gap displacement during compression molding for making UD composites. First material group is composed of 4 kinds of thermoplastic composite materials. The other is thermoplastic film stacking with opened and unopened reinforcing fiber tows. Microscopic observation on the cross-section of parts fabricated at various molding time and measurement of transverse bending strength of these parts were also conducted. Based on the theoretical model proposed in the first part and these experimental data, impregnation behaviors of these materials were systematically discussed. The results suggest basic technological ways for attaining good impregnation in thermoplastic composites.
Polymer Pellet Flow out of the Hopper into the First Section of a Single Screw
Authors: Potente H. , Pohl T. C. 
Published: December 2013

Abstract
The flow of plastic pellets into the first section of a single screw is frequently neglected when analyzing the solids conveying process in single screw machines. In order to get a better insight into the complex correlations that exist between pellet properties, barrel and screw geomtry a physical-mathematical model is presented. As a result the pellet inflow behavior and the degree of filling in the first channel of the screw can be determined.
Modification of Polyolefin with Maleic Anhydride/Styrene and Methyl Methacrylate/Styrene
Authors: Cha J. , White J.L. 
Published: December 2013

Abstract
There has been little effort to quantitatively understand the simultaneous graft copolymerization of two monomers in batch and continuous mixers. In this study maleic anhydride/styrene and methyl methacrylate/styrene monomer pairs were grafted onto polypropylene in both an internal mixer and a twin screw extruder. There is little information on the evolution of grafting reactions of dual monomers with respect to time in an internal mixer and along the screw axis in a twin screw extruder. The influence of reaction time in an internal mixer and residence time in a twin screw extruder on degree of grafting was measured. The dependence of the degree of grafting with respect to ratio of comonomer concentration was determined. A kinetic scheme was proposed and experimentally tested.
Resonant and Invariant Advection in Single-Screw Extrusion
Authors: Hwang W. R. , Kwon T. H. 
Published: December 2013

Abstract
In this paper, we discussed how unmixed and well-mixed zones are determined by the practical design parameters of the Chaos Screw (CS) system for the single-screw extruder, e. g. the helix angle, the magnitude of adverse pressure gradient, and the fraction of no-barrier zone. The key concept is the frequency ratio distribution of the unperturbed system. Through the extensive three-dimensional numerical simulations with finite element methods and particle tracing techniques, successive creation and breakup of resonant orbits and KAM tori in terms of design parameters are presented. The results show that one can predict the spatial configuration of well-mixed and unmixed zones from the frequency ratio distribution and the amount of the perturbation strength. Finally, the exit time distributions caused by dynamical structures are discussed.
Modelling of the Flow in the Distribution Plate of a Spin Pack
Authors: Béreaux Y. 
Published: December 2013

Abstract
A Computational Fluid Dynamics analysis of the flow through the distributionplate of a fibre spinning pack has been performed. The features of the flow that are relevant to polymer processing are addressed, such as the wall shear rate, residence time and dead zones. An analyticalmodel, that agrees very well with the calculations, is proposed. It also yields insight into the role played in the flow by different design parameters of the distribution plate. This model, primarily based upon a Newtonian fluid, is also extended to a shear thinning one.
A Comparison of the Axisymmetric and Planar Elongational Viscosities of PE-LD
Authors: Beaupre P. , Gupta M. 
Published: December 2013

Abstract
The elongational viscosities of a low density polyethylene in axisymmetric and planar flows are compared. The experimental data on entrance pressure loss is matched with the corresponding finite element predictions to estimate the parameters in the elongational viscosity model proposed by Sarkar and Gupta. The entrance losses in the capillary and slit rheometers are used to predict the elongational viscosities for axisymmetric and planar flows respectively. The power-law region of the axisymmetric as well as planar elongational viscosity is found to follow the time-temperature superposition principle. The vortices encountered in the flow near the abrupt contraction for the planar and axisymmetric cases are compared. The vortex near the abrupt contraction is found to reduce in size as the flow rate is increased for planar as well as axisymmetric entrance flow.
A New Method to Determine the Filament Force Tension within the Fibre Formation Zone
Authors: Brünig H. , Tändler B. 
Published: December 2013

Abstract
A non-contact method to determine the force tension of the spinning line is proposed by a non-vertical arrangement of the melt spinning equipment. The curvature of the spinline caused by gravitation was determined experimentally by measuring the spinline location. This is the key for the calculation of the filament force only by geometric measurements.
Investigation of the Interfacial Instabilities in the Coextrusion Flow of PE and PS
Authors: Valette R. , Laure P. , Demay Y. , Agassant J.-F. 
Published: December 2013

Abstract
The interface instability of the coextrusion flow of a polyethylene and a polystyrene is experimentally studied with industrial and laboratory equipments for various flow rates and temperature. Stable and unstable coextrusion conditions are identified as a function of flow rate ratio, shear rate and temperature. It is found that temperature and flow rate ratio are the most relevant parameters. Experimental results are then compared with stability analysis assuming White-Metzner constitutive equations. Agreement is fair at temperatures of 180°C and 200°C. However the longwave stability analysis is not sufficient to predict all experimental data.
Flow Effects on Polymer Transesterification
Authors: Yang I.-K. , Hong C. Y. , Pan P. H. 
Published: December 2013

Abstract
Transesterification between poly–ε–caprolactone (PCL) and polyethylene-terephthalate (PET) under shear flow was investigated. Two types of flow were imposed to the test samples; one is a simple shear and the other is an oscillatory shear. Comparing to reaction at quiescent state, flow provides better conversion to the reaction. For simple shear flow, the rate of reaction increases as the shear rate increases, while under oscillatory flow, increasing the frequency and the amplitude enhances the extent of reaction. Improvements of the transesterification rate by simple shear prevail over those by the oscillatory motion. The results imply that the transesterification is mass transfer limited. The improvement of the reaction rate and the prevalence of the simple shear flow can be interpreted by the convective effect. The small margin between the rates of reaction under flow and at rest can be attributed to the small Reynolds number of the system.