bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control Strategies for Cyclic Polymer Processes
Authors: Ralston P. , Wright A. , Stoll K. , Harper D. 
Published: December 2013

Abstract
This paper presents the simulation of a typical cyclic polymer processing operation with respect to the performance of different control strategies for part quality when subjected to disturbances with realistic load-profiles. Disturbances enter the simulation in a complex, probabilistic manner creating a unique flexibility in load representation which helps the simulation more accurately capture the performance of real processing operations. Realistic simulations can provide necessary information and be less costly than benchmark studies on actual processes. The objective of the research is to examine the effect of different control strategies on the overall control of part-to-part quality, not the control of the continuous processes that occur in part fabrication. The performance of six different control strategies is compared; two strategies are conventional feedback, and four strategies are statistically based. The statistically based algorithms effect closed loop control, but only when a true load exists. Results are analyzed using statistical analysis of variance (ANOVA) via a completely randomized block experimental design, and Duncan's multiple range test is used to rank the control strategies. The results indicate that as more disturbances enter the system, the conventional controllers perform better than the other strategies. When fewer disturbances are present, however, the statistically based controllers perform better. The most notable result is that one statistically based controller, the Western Electric runs rules controller, performs well over the entire range of disturbances.
Design of Tightly Intermeshing Co-Rotating Twin Screw Extruders
Authors: Potente H. , Ansahl J. , Klarholz B. 
Published: December 2013

Abstract
Composite models for the calculation of the filling level profiles, the pressure profiles, the melting profiles, the residence time distributions, the temperature profiles, the shear stress profiles, and the power consumption in modular tightly intermeshing co-rotating twin screw extruders (ZSK) are developed. A complex systematic design procedure was compiled, which is explained in part in this paper. The simulation of the intermeshing co-rotating machine involves both screw and kneading disc elements, including left- and right-handed sections. Kneading blocks were approximated by a screw of “equivalent pitch” with making allowance for the leakage flow across the flights from one channel to the adjacent channel. The mathematical treatment of co-rotating twin screw extruders has been based up according to the theory of single screw extruders. There was seen to be a good correlation between calculated and experimental results.
Devolatilization of Polymer Solutions
Authors: Chen L. , Hu G. H. , Lindt J. T. 
Published: December 2013

Abstract
A simulator to emulate the working of a counter-rotating twin screw extruder was constructed for studying devolatilization (DV) of reactive polymer solutions. The rate of the release of the volatiles was measured by an in-line mass flow meter. The operating pressure and solution temperature were measured by a pressure transducer and a thermocouple. The vapor sample compositions were determined by UV spectrophotometer. The transesterification of ethylene-vinyl acetate copolymer with 3-phenyl 1-propanol in 1-nonane solution was chosen as a model reaction. The volumetric mass transfer coefficient K1A was determined at various temperatures, pressures, shaft speeds and sample sizes. The effect of the reaction on K1A was also examined. It was found that K1A of the solvent (1-nonane) increases significantly with a decrease in operating pressure, and that it also increases appreciably with shaft speed, whereas temperature and the initial sample size have little effect on it. The reaction shows undetectable effect on K1A of the inert solvent.
Cooling and Wall Thickness Uniformity in Plastic Pipe Manufacture
Authors: Pittman J. F. T. , Whitham G. P. , Beech S. , Gwynn D. 
Published: December 2013

Abstract
A mathematical model of cooling and solidification, coupled with gravity induced flow during the cooling of extruded plastic pipe is set up and solved by the finite element method. Detailed and comprehensive experimental data are obtained from a commercial extrusion line producing 315 mm O.D. SDR 11 MDPE pipe using vacuum sizing and external spray cooling, including temperatures measured within the pipe wall using embedded thermocouples, which are carried down the entire cooling line.
The computer simulations are successfully fitted to experimental temperatures by adjusting transfer coefficients for the outer surface. The deduced values are: tank (1) (vacuum) 750 W/m2 K; (2) 200 W/m2 K; (3) 150 W/m2 K. Heat loss to the bore is shown to be negligible. Predicted final pipe wall thicknesses – starting with a concentric extrudate – agree within 4 % with measured values. Wall thickness variation is predicted to be 16.6 %, compared with 13.9 % measured.
High-Speed, Non-Isothermal Fiber Spinning
Authors: Papanastasiou T. S. , Alaie S. M. , Chen Z. 
Published: December 2013

Abstract
Spinning of PET fibers of low elasticity at high speed, and of polypropylene (of moderate elasticity) and polystyrene (of high elasticity) under non-isothermal conditions that contain their glass transition temperature, is analyzed by means of a unique BKZ-type constitutive equation that is augmented by the appropriate form of shift factors to apply in both, the rubbery and the glassy states of amorphous polymers. This approach eliminates the necessity of tracking the glassification point by trial and error, required in attempting to match different constitutive laws across it. Predictions of velocity and temperature distribution along the PET fiber agree with available experimental data, and the predicted glass transition point of polystyrene occurs indeed at about its glass transition temperature. Comparisons of predictions to those with an inelastic constitutive equation show that they apply to PET (of low elasticity) alone.
Finite Element Modelling of Non-isothermal Viscometric Flows in Rubber Mixing
Authors: Nassehi V. , Salemi R. 
Published: December 2013

Abstract
Attempts to find a general viscoelastic fluid model which would be applicable to all different classes of flow problems and could produce experimentally verifiable results, have so far failed. Instead efforts have been concentrated in finding a suitable viscoelastic model for the particular class of flow problem in hand. Bearing this in mind, a simple viscoelastic fluid model which has shown promising results for cases where there is a dominant flow direction (i.e. the flow is viscometric) is considered here. Such conditions may occur inside a rubber mixer where in cylindrical coordinate system (r,θ,z), the elastomer is flowing dominantly in θ direction. This paper deals with the Galerkin finite element modelling of viscometric flows under non-isothermal conditions. The novel aspect of this work is the extension of the application of a viscometric constitutive equation known as (CEF) model to the simulation of predominantly circumferential flow in a two-dimensional representation of an internal mixer using polar coordinates. For a given set of boundary conditions, the mathematical model can simulate the velocity, pressure and temperature fields inside a mixer. Comparison of the numerical results with the available experimental evidence confirm the general validity of the mathematical model used.
Modification of Polypropylene by Maleic Anhydride
Authors: Martínez J. Ma. Ga. , Taranco J. , Laguna O. , Collar E.P. 
Published: December 2013

Abstract
The Box-Wilson experimental design method is employed to study the free radical process between polypropylene and maleic anhydride in the presence of a peroxide like radical initiator. The batch processes in the solution and in the molten state have been considered in an attempt to know how the physical characteristics of the reaction medium are affecting the modification level of the polypropylene. The analytical titration method proposed by Gaylord is used in order to evaluate the maleic anhydride grafting onto the polypropylene. The main goal of this preliminary study is to know and to show the quantitative values reached in the grafted maleic anhydride level inside the experimental range scanned. From the results the influence of the reaction and several observations can be made in order to evaluate and finally optimize the continuous process by reactive extrusion.
Extrusion of Short Fibre Reinforced PP
Authors: Dospis~il D. , Kubát J. , Plešek M. , Sáha P. 
Published: December 2013

Abstract
Data regarding the influence of screw geometry on homogeneity and fibre length reduction during single screw extrusion of short glass fibre reinforced PP are presented. Three screw geometries, two grades of PP with different melt flow indices, and four levels of filling (10 to 40 wt.%) were the main variables studied. The fibre breakage mechanism was evaluated with respect to solid and melt conveying and melting mechanisms in the screw channels. The screw with a long compression zone produced a material of poor homogeneity, a stable melting mechanism and a medium level of fibre length reduction. The very short compression zone screw produced unstable melting which considerably improved the homogenization process of the fibres in the polymer matrix. In this way the extrudates remained smooth up to the 30 wt.% filling level. The homogeneity was comparable to that obtained by a process including two steps of compounding: twin screw and single screw extrusion. However, the fibre degradation in the screw with a very short compression zone was substantially lower than in the process including two compounding steps.
An Experimental Study of a Bicomponent Coextrusion Fiber Spinning
Authors: Lee W.-S. , Park C.-W. 
Published: December 2013

Abstract
The draw resonance instability in a concentric bicomponent coextrusion fiber spinning has been studied experimentally using a linear low density polyethylene (LLDPE) for the core and two low density polyethylenes (LDPE) for the skin-layer. These materials have been chosen to investigate a coextrusion flow in which each components have quite different extensional rheology. When they were spun individually, the LLDPE showed the draw resonance at a certain critical draw ratio whereas the LDPEs did not show the oscillatory instability. When the LLDPE and LDPE were spun together, the presence of the more viscoelastic LDPE layer delayed the onset of draw resonance of the LLDPE to a higher draw ratio. The degree of changes in the critical draw ratio was observed to be dependent on the rheological properties of the LDPEs. Although the experiments were conducted in a non-isothermal condition, various aspects of the experimental observations appeared to be in qualitative agreement with the predictions of isothermal linear theories. The present study is specifically for a coextrusion fiber spinning. Nevertheless, the observed trend of the instability should be also relevant to other coextrusion processes such as extrusion coating or film casting.
Blends of PVC with Miscible Polymers
Authors: Nakajima N. , Kwak S.-Y. 
Published: December 2013

Abstract
Polymer blends consisting of miscible components may form single phase structures; however, it requires solution blending to ensure complete homogeneity. For a large scale mixing, however, mechanical blending is the common practice. The resulting blends are homogeneous on the macroscale, but often contain microscopic domains of the component polymers as well as domains of mixed phases. This work describes mechanical blends of PVC with miscible polymers (nitrile rubber, poly-e-caprolactone, and a copolyester thermoplastic elastomer). The complex morphology of these blends has been studied and identified by means of the frequency- and temperature-dependence of their viscoelastic behavior.
Polyarylamide/Polypropylene Blends
Authors: Haddout A. , Villoutreix J. , Villoutreix G. 
Published: December 2013

Abstract
This work deals with the experimental study of the rheological behaviour, the growth and evolution of the morphology of two components polyarylamide/polypropylene blends during injection molding. In the case of compatibilized blends, the viscosity shows two main results depending on shear rate. For low shear rates, up to 103 s−1, we notice a positive deviation in comparison with the additivity low, whereas a negative deviation is observed for high shear rates including injection molding conditions. The analysis of the morphology of the blend by scanning electronic microscopy shows a dispersed phase with nodules. The injection flow rate acts on the shape of the nodules and also on their repartition as obtained from a rectangular molded plate. The thermomechanical analysis of pure composition samples (100 % PA) and of a compatibilized mixture PA (70 %)/PP (30 %) has been studied.
Flexural Stiffness of Injection Molded Glass Fiber Reinforced Thermoplastics
Authors: Xia M. , Hamada H. , Maekawa Z. 
Published: December 2013

Abstract
Using a simulated laminated-plate model, an analytical method is presented for predicting stiffness of fiber reinforced injection moldings including the effects of fiber orientation and fiber length distributions. The mechanical properties of fiber reinforced composites depend not only on the elastic properties and the volume fraction of the constituent materials, but also on the fiber orientation and fiber length distributions in the molding. In this study, two probability density functions are proposed for modeling the distributions of fiber orientation and fiber length in the injection moldings, respectively. Inserting the fiber orientation and fiber length distributions into the components of the stiffness constant, the elastic moduli of the fiber reinforced injection moldings are predicted on the basis of a generalized laminated-plate theory.
Morphology in Blends of a Thermotropic Liquid Crystalline Polymer and Polypropylene
Authors: Sabol E. A. , Baird D. G. 
Published: December 2013

Abstract
By monitoring the development of morphology a novel dual extrusion process from the point that the thermotropic liquid crystalline polymer (TLCP) stream meets the matrix material to the final drawn strand, a clear mechanism for the development of the TLCP reinforcement is presented. It was found that under appropriate mixing configurations the fibrillar TLCP morphology seen in strands produced from this method originate at the onset of mixing in the phase distribution system and are subsequently refined as the melt passes through the static mixing elements. The axially continuous morphology seen at the entrance of the die is maintained and further developed as the blend passes through the die and is drawn. In contrast, strands produced using the single extruder blending or the dual extrusion method with excessive mixing produce a droplet morphology prior to the die. At a very low concentration of TLCP, the droplets are too small and well dispersed to sufficiently coalesce and deform into fibrils in the elongational flow field of the die and drawing process. These phenomena result in an undesirable morphology for self reinforcement which clearly has been seen in the measured mechanical properties of the strands.
Viscosity and the Formation of Die Drool at the Polymer-Metal Interfaces
Authors: Chan Chi-Ming 
Published: December 2013

Abstract
The effects of the die-wall material on the apparent viscosity of a blend of Hytrel and Viton and on the formation of a particle-like material, which is commonly referred to as die drool, at the polymer-metal interface were studied. The blend, which consisted of approximately 15 % Viton and 85 % Hytrel, was prepared by using a twin-co-rotating-screw extruder. During extrusion of this blend, small particles appeared on the surface of the extrudates; these particles were determined by XPS to be a material which consisted largely of Viton. The apparent viscosity of the blend and the amount of die drool were found to decrease as the surface energy of the material used for the construction of the die decreased. The reduction in the production rate of die drool is attributed to reduction of adhesion at the interface.
Biaxially Oriented Polyethylene Films by Compression of Injection Moldings
Authors: Bayer R. K. , Ania F. , Calleja F. J. Baltá 
Published: December 2013

Abstract
The tensile strength, σ, of biaxially oriented polyethylene (PE) films with various degrees of biaxial stretching has been measured. The dependence of σ in the two principal directions x and y is investigated as a function of two parameters: the biaxial draw ratio (average draw ratio of the film) and the degree of biaxiality (strain distribution along the principal directions). Both parameters are related to the final applied pressure PF. The influence of initial orientation and anisometry of the injection molded precursors on the final σx and σy values along the principal directions is studied. Results are discussed in the light of the deformation mechanism which transforms the original uniaxial fiber structure of the moldings into the biaxial fibrillar structure of the final films. Direct evidence of this transformation is provided by small angle X-ray scattering (SAXS).
A Study of Distributive Mixing in Counterrotating Twin Screw Extruders
Authors: Li T. , Manas-Zloczower I. 
Published: December 2013

Abstract
Counterrotating twin screw extruders are widely used for compounding, devolatilization, blending, and reactive extrusion. A fluid dynamics analysis package-FIDAP, using the finite element method, was implemented to simulate the 3-D, isothermal flow patterns in intermeshing and tangential counterrotating twin screw extruders. The rheology of the fluid was described by a power-law model. We developed a framework to evaluate the distributive mixing efficiency. The dynamics of distributive mixing were studied numerically by means of tracking the evolution of particles originally gathered as clusters. The extent or goodness of mixing was characterized in terms of length stretch, pairwise correlation function and volume fraction of islands. The length stretch reflects the capability of the mixer to spread particles away from their neighbors initially present in the same cluster. The pairwise correlation function characterizes the global distribution of particles in the mixing region. The volume fraction of islands quantifies the regions void of minor component and provides the local analysis of mixing. This framework can then be used to differentiate among various operating conditions or various designs of the same type of equipment.
Comparative Wide-angle X-ray and Microscopical Studies on the Layered Structure in Injection Molded Polypropylene Disks
Authors: Zipper P. , Abuja P. M. , Jánosi A. , Wrentschur E. , Geymayer W. , Ingolic E. , Friesenbichler W. 
Published: December 2013

Abstract
Circular disks (280 mm diameter, 2 mm thickness) were injection molded from isotactic polypropylene under systematic variation of processing parameters (melt temperature, mold temperature, screw velocity, packing pressure, and packing time). Sections were taken from the disks perpendicular to their surface, at 40 mm distance from gate, in different orientations, and were investigated by means of optical microscopy using polarized light and by spatially resolved wide-angle X-ray scattering. The results from X-ray scans of the cross-sections are presented in terms of several parameters characterizing the state of orientation of α-PP crystallites and the relative amount of β-PP crystallites. The profiles of the various X-ray parameters versus the distance from surface deliver a detailed picture of the layered structure of the cross-sections which is supported and supplemented by micrographs taken with polarized light. The comparison of the results obtained for disks molded under different conditions unveils clear correlations between processing parameters and morphological characteristics of the disks.
Tool Heat Transfer Analysis in Resin Transfer Molding
Authors: Wang T. J. , Lin R. J. , Lee L. J. 
Published: December 2013

Abstract
This work presents four different numerical approaches to analyze heat transfer in the mold halves. The formulations, numerical methods and simulated results of each method are presented and compared to the experimental results based on a metal (aluminum) and a non-metal (reinforced epoxy) molds. Several examples are also presented to show the importance of tool heat transfer analysis in reactive processing.
Injection Molding of Microcomposites Based on Polypropylene and Thermotropic Liquid Crystalline Polymers
Authors: Handlos A. A. , Baird D. G. 
Published: December 2013

Abstract
This work is concerned with the injection molding of pellets of polypropylene (PP) containing pregenerated microfibrils of thermotropic liquid crystal polymers (TLCPs), referred to as microcomposites. The TLCPs used are HX6000 and Vectra A950. The microcomposites are produced by drawing strands of PP and TLCPs generated by means of a novel mixing technique and pelletizing the strands. The work was undertaken in an effort to improve on the properties observed for in situ composites in which the TLCP fibrils are generated during mold filling. In situ composites usually exhibit highly anisotropic mechanical properties and the properties do not reflect the full reinforcing potential of the TLCP fibers. Factors considered include the effect of in situ composite strand properties on the properties of the injection molded composite, the melt temperature used in injection molding, TLCP concentration, and the melt temperature of the TLCP. It is found that when processed at appropriate temperatures, the TLCP microfibrils are maintained through injection molding, and the composites show a good balance between machine and transverse direction properties (with ratios of the machine and transverse direction moduli ranging from 1.1 toto 1.35). The use of HX6000 rather than Vectra A allows for higher processing temperatures to be used during injection molding. The moduli of the injection molded composites increase with both increasing TLCP composition and in situ composite strand moduli. At 10 wt.-% TLCP the moduli of the injection molded composites approach the predictions of composite theory while at 20 and 30 wt.-% TLCP negative deviations from the theoretical moduli are seen. This is believed to be the result of a loss of fiber aspect ratio from fiber breakage and agglomeration. It is believed that with future studies on the effect of shear and elongational stresses during processing on the aspect ratio of the fibers a means of overcoming this problem may be found. The modulus of a 20 wt.-% HX6000 composite is similar to that of a 20 wt.-% glass composite (3.21 GPa versus 3.66 GPa), but the tensile strength of the HX6000 composite is about 28 % lower than that of the glass composite. It is expected that as the modulus and strength of the reinforcing TLCP fibrils are improved the properties of the injection molded microcomposites should exceed those of glass reinforced composites.
An Analytical Model of the Conveying Behaviour of Closely Intermeshing Co-rotating Twin Screw Extruders
Authors: Michaeli W. , Grefenstein A. 
Published: December 2013

Abstract
Closely intermeshing, co-rotating, twin-screw extruders are increasingly being used for polymer preparation and reactive extrusion. For a theoretical description of these processes, not only the mechanism of reaction kinetics but also aspects of heat transfer and in particular the conveying behaviour of modular twin-screw extruders must be taken into account. Using practical examples, this work sets out to evaluate the possibility of predicting process parameters such as melt temperature, drive power, degree of filling and pressure build-up as functions of screw geometry. To this end, trials with two twin-screw extruders of different size were carried out.