bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Zinc Fatty Acids on Improved Polymer Processing for Critical Extrusions
Authors: Kim K.-J. , VanderKooi J. 
Published: December 2013

Abstract
The processability of TESPD coupled silica-black-solution SBR with zinc fatty acids (EF and ZB) in an internal mixer and extruder was investigated. The processability, rheological property, and vulcanization property of their composite were measured as a function of storage conditions including time and humidity and as a function of mixing sequence (1P and 2P).
Processing through a single screw extruder, processing additive, zinc fatty acid, added compounds exhibited lower pressure build up than without-additive compound (Control) and their viscosities were lower than the Control. The EF-2P and the ZB-2P compounds exhibited lower pressure build up than the EF-1P and the ZB-1P ones, respectively. The Mooney viscosities of both the dry and the humid exposed ones increased as the storage time increased and the viscosities of the humid exposed compounds exhibited slightly higher than the dry ones.
The cure times of the humid exposed compounds were shorter than that of the dry ones, and as the storage time increases, the cure time of the dry ones were varied depending on mixing sequence; however that of the humid exposed ones were decreased.
The torque rises (MH-ML) of the humid exposed compounds were higher than that of the dry ones as the storage time increases, and while the torque rises of the dry compounds tend to remain constant that of the humid exposed ones increased.
Processing additive added compounds (EF-1P, EF-2P, ZB-1P and ZB-2P) exhibited lower modulus and longer cure time than the Control.
Investigation of Melting Phenomena in Modular Co-rotating Twin Screw Extrusion
Authors: Jung H. , White J. L. 
Published: December 2013

Abstract
An experimental investigation of the mechanisms of melting of polyolefins in a modular co-rotating twin screw extruder was carried out as a function of (i) barrel temperature including below the melting temperature (ii) screw speed and (iii) feed rate. The modular screws were removed from a twin screw extruder following experiments where pellets of linear low density polyethylene or isotactic polypropylene had been fed and processed under steady state conditions. The modular screws contained thermoplastic carcasses. These were sectioned and removed as well as inspected.
Three melting initiation regimes were identified. These were (i) melting initiated from barrel, (ii) melting initiated from screw, and (iii) melting initiated in the bulk. At high barrel temperatures mechanism (i) is observed, at lower barrel temperatures and slower screw speeds mechanism (ii) is found, and at lower barrel temperatures and higher screw speeds mechanism (iii) is observed. The propagation of the melting process was also investigated. Pellet bed instabilities are usually involved at higher screw speeds. We discuss modeling of these mechanisms.
Structure Development in Injection Molding of Isotactic Polypropylene, its Blends, Compounds and Dynamic Vulcanizates
Authors: Yu Y. , White J. L. 
Published: December 2013

Abstract
We make a comparative study of structure development in injection molding of isotactic polypropylene, polypropylene blends/compounds and dynamically vulcanized polypropylene thermoplastic elastomers (TPVs) WAXS 2θ scans were used to determine crystalline forms and the distribution of relative amounts of crystalline forms through the cross-section of injection molded parts. WAXS film patterns, polarized optical light micrographs and birefringence were used to qualitatively indicate polymer chain orientation variation through the cross-section. We also used WAXS pole figures to investigate polymer crystalline orientation and filler orientation in different layers of the injection molded parts.
It was found that a low or modest orientation layer exists on the part surface. There is an intermediate highly oriented layer in the parts of isotactic polypropylene and most polypropylene blends/compounds. The interior of the parts was spherulitic and increasingly isotropic as one moved to the center. The thickness of the surface layer increases as the injection pressure decreases. The layer was not observed in parts of dynamically vulcanized polypropylene thermoplastic elastomers. This would seem to be associated with the TPVs possessing a yield stress and not exhibiting substantial fountain flow in mold filling.
Impact Strength of β-Nucleated Polypropylene
Authors: Obadal M. , Čermák R. , Baran N. , Stoklasa K. , Šimoník J. 
Published: December 2013

Abstract
Structural transformations of semicrystalline polymers form an important field of current scientific research. The preparation of controlled supermolecular structure may lead to significant improvements in mechanical, thermal and optical properties. As for isotactic polypropylene (iPP), its properties essentially depend on its crystalline phase composition, which is due to polymorphism of iPP. Thus, the aim of this work is to analyze the influence of the β-phase content in polypropylene and of its spatial arrangement on mechanical properties, in particular on its impact strength. Commercially available isotactic polypropylene (iPP) was modified by various amounts of a specific β-nucleating agent (N, N'-dicyclohexylnaphtalene-2,6-dicarboxamide). From the prepared mixtures standard impact testing bars were injection molded. The structure of the specimens was studied by X-ray diffractometry, and impact properties were determined using Charpy impact tester. It was found that addition of the nucleator led to β-phase content increase, especially in the core region of the injection molded samples. The skin (surface layer of the samples) contained lower amount of β-phase. Furthermore, notch impact strength dramatically increased with increasing concentrations of the β-nucleating agent. The concentration of 0.03 wt.% of the nucleator can be considered a “boundary value” due to the fact that the maximum notch impact strength value was reached. With further addition of the nucleating agent the impact strength slowly decreased. Therefore it should be noted that the improvement of impact properties is not only due to the presence of β-phase, but also there are some synergy-applied factors – such as the structural heterogeneity and spatial arrangement of the β-phase in injection molded samples.
Microinjection Molding with LIGA-Like Process
Authors: Yang S.-P. , Young W.-B. 
Published: December 2013

Abstract
Injection molding process is used to mold component with microstructures in this study. The mold insert with microstructures having an aspect ratio around one is fabricated by the LIGA-Like process. This LIGA-Like process combines the UV-Lithography and electroplating to define the microstructure on a steel substrate. The method provides a cost effective way for molding a microstructure without the X-ray lithography. In fabrication of the mold insert, well-defined draft angle of the sidewall at the structure is a crucial factor for successful molding. The molded component has a good replication of the microstructures in the mold insert.
Numerical and Physical Modeling of Polymer Crystallization
Authors: Monasse B. , Smirnova J. , Haudin J.-M. , Chenot J.-L. 
Published: December 2013

Abstract
Crystallization of thin polypropylene films was performed in isothermal, constant cooling-rate and mixed conditions. The experiments were first analyzed using the classical procedures based on simplified forms (Avrami, Ozawa) of the general Kolmogoroff-Avrami-Evans (KAE) theory. These analyses, which can be applied over an unusually wide transformation range, show that the crystallizations are actually 2 D. Then, a procedure has been established for the determination of the nucleation and growth parameters involved in the theoretical model presented in the first paper of this series. These parameters have been introduced into the model in order to predict the crystallization behavior in isothermal, constant-cooling-rate and mixed-conditions: transformed fraction, number of activated nuclei, final size distribution of semi-crystalline entities. A very good agreement is generally found between predictions and experimental results.
Modelling of Cyclic 3-Dimensional Heat Transfer in Injection Moulding
Authors: Polynkin A. , Pittman J. F. T. , Sienz J. 
Published: December 2013

Abstract
A detailed 3-dimensional analysis of cyclic heat transfer in a complex injection moulding mould tool has been carried out, using a general-purpose commercial heat transfer code (FIDAP). A novel, generally applicable technique for modelling of heat loss to ambient from the tool parting surfaces is introduced, to facilitate inclusion of the mould-open period in the modelling. Simulations are continued through 30 cycles of moulding, to attainment of steady periodic conditions. During this period temperatures at the polymer-steel interface rose by between 10 °C and 40°C above the coolant temperature. At the start of cooling, values of cavity surface heat transfer coefficients referred to the coolant temperature ranged from approximately 4000 W/m2K to 400 W/m2K, with the highest values occurring directly below the cooling channels and the lowest near a heated sprue bush. At the end of the cooling period, values at each location had dropped by approximately an order of magnitude. These results illustrate the limitations of plastics cooling analyses that use constant values of temperature or heat transfer coefficients as boundary conditions on the cavity surface. Comparison with results obtained omitting the modelling of the mould-open period shows how, in the latter case, higher tool temperatures are attained in the steady periodic conditions, and a larger number of cycles are required to reach steady periodic conditions.
Melt Fracture of Linear PE
Authors: Muliawan E. B. , Hatzikiriakos S. G. , Sentmanat M. 
Published: December 2013

Abstract
In this paper we studied the melt fracture behaviour in capillary flow of a number of polyethylenes produced by various technologies. The critical shear rates for the onset of both sharkskin and gross melt fractures were found to correlate with the high-rate extensional flow behaviour of the polymers. These findings were found to mechanistically support the generally accepted observations of melt fracture occurring at the exit (sharkskin) and entrance (gross) regions of the capillary die. In addition, it was found that boron nitride (BN) behaves as an energy dissipater that suppresses the rapid increase of extensional stress associated with gross melt fracture. This enables BN to act as an effective processing aid in postponing gross melt fracture in the extrusion of polyethylenes.
Design Sensitivity Analysis for the Optimization of the Injection Molding Process
Authors: Ilinca F. , Hétu J.-F. , Pelletier D. 
Published: December 2013

Abstract
This paper presents an application of the Continuous Sensitivity Equation Method (CSEM) for the optimization of the injection molding process and its three-dimensional (3D) simulation by the finite element method. Finding the proper combination of process parameters such as injection speed, and melt and mold temperatures is critical to achieving a part that minimizes warpage and has the desired mechanical properties. Very often a successful design in injection molding comes at the end of a long trial and error process. Design Sensitivity Analysis (DSA) can help manufacturers improve their designs and can produce substantial savings in terms of both time and money. This work explores the ability of sensitivity analysis to predict the effects of design parameters on the performance of an injection molding process. The paper presents results of a 3D finite element solution of the filling stage of the injection molding process. Sensitivities of the solution with respect to different process parameters are computed using the continuous sensitivity equation method. Solutions are shown for the non-isothermal filling of a rectangular plate with a polymer melt behaving as a non-Newtonian fluid. The paper presents the equations for the sensitivity of the velocity, pressure and temperature and their solution by a finite element method. Sensitivities of the solution with respect to the injection speed, the melt and mold temperatures and to the heat transfer coefficient at the cavity/mold interface are shown.
Using Multi-Objective Evolutionary Algorithms to Optimize Mechanical Properties of Injection Molded Parts
Authors: Gaspar-Cunha A. , Viana J. C. 
Published: December 2013

Abstract
An automatic optimization methodology based on Multi-Objective Evolutionary Algorithms (MOEA) is proposed to optimize the mechanical properties of injection molded products. For that purpose an MOEA is linked to a commercially available mould filling computer simulator code, CMOLD. The developed optimization methodology was applied to a practical case study where the processing conditions are optimized as a function of a desired morphological state (skin thickness, degree of crystallinity and/or level of molecular orientation; these latter are interpreted in terms of thermomechanical indices) and envisaged mechanical performance at two strain rates levels (of the order of 10–4 and 102 s1). Generally, the optimization methodology proposed is able to take into account the influence of the process parameters and produce solutions that are physically consistent. The processing conditions maximizing the morphological state of the moldings and their mechanical performance are identified. This latter is firstly maximized individually for distinct strain-rates and then a simultaneous optimization for both low and high strain-rate response is performed. The optimized sets of processing conditions leading to the maximization of the mechanical performance are analyzed by the computation of two thermomechanical indices aiming at interpreted the resultant morphological state of the moldings.
Modelling Flow in an Intermeshing Co-rotating Twin Screw Extruder: Flow in Kneading Discs
Authors: Szydlowski W. , Brzoskowski R. , White J. L. 
Published: December 2013

Abstract
A model for simulation of flow in an intermeshing kneading disc region of corotating twin screw extruder is presented. This is based on hydrodynamic lubrication theory for a Newtonian fluid. Numerical procedures are used to compute the pressure distribution and flow field in the kneading disc region. The influence of staggering angle, nip clearance, screw speed and throughput rate are investigated.
The Fibrillar Structure of Melt Spun and Drawn PP Filaments
Authors: Bodaghi H. , Spruiell J. E. , White J. L. 
Published: December 2013

Abstract
A basic study of fibrillation and void development during drawing of melt spun polypropylene filaments is presented. The filaments are characterized by small angle x-ray scattering (SAXS), density, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), wide angle x-ray diffraction (WAXS), and birefringence. The latter two methods were used to characterize the molecular orientation produced by processing while SEM studies of peeled filaments revealed, qualitatively, the development of the fibrillated internal superstructure. The volume fraction of microvoids was computed from the intensity of SAXS and from a combination of DSC and density measurements. The microvoid fractions determined by these two techniques were in good agreement. The volume per cent of microvoids varied from 0.04 to 2.8%. It was found that the fibrillation observed qualitatively by SEM and the measured volume fraction and number density of microvoids increased with (i) increase in draw ratio, (ii) decrease in draw temperature, (iii) increased orientation of melt spun filaments, and (iv) increased molecular weight of the polypropylene. Using Guinier analysis of the SAXS data it was found that the voids had dimensions of 25–40 nm, parallel to the fiber axis and of order 15 to 30 nm perpendicular to the fiber axis. As the drawing temperature increased the SAXS void size increased and void number density decreased. The longitudinal mechanical properties of the fibers were found to be mainly a function of the orientation and were not very much affected by changes in fibrillation or void structure per se.
Modelling the Packing Cooling Stage in Injection Molding of Amorphous Polymers
Authors: Huilier D. , Terrisse J. , de la Lande M.-E. , Latrobe A. 
Published: December 2013

Abstract
The interaction between flow, heat transfer and thermodynamic behavior of amorphous polymers during packing-cooling stages in injection molding of thermoplastics has been studied numerically. A finite-volume method with staggered meshes has been used to solve simultaneously the continuity, momentum and energy equations coupled to an equation of state. The Generalized Newtonian (GN) fluid model has been chosen, including pressure effects during packing. The simulation, applied to a polystyrene melt injected into a rectangular shaped cavity, allows the calculation of the pressure, velocity and temperature distributions during the packing and cooling phases. The final shrinkage of the resulting molded part is also calculated.
Dynamic Simulation of Suspensions of Non-Spherical Particles by Boundary Element Techniques
Authors: Boyington D. R. , Soane D. S. 
Published: December 2013

Abstract
A method is developed for the simulation of the transient structure and rheology of concentrated suspensions of generally-shaped particles. This procedure is a modification of the Stokesian dynamics method using boundary element to evaluate the multiple interactions of an arbitrary number of particles. The effect of commonly-used pairwise additivity assumptions on the particle velocities and suspension stress is shown for several three-spheroid structures. In general, superposition of forces gives better results than additivity of disturbance velocities. Methods for improving the simulation and an experimental program to measure the transient particle orientations and viscosity of concentrated suspensions are discussed.
Flow of Rubber Compound in a Pin Barrel Screw Extruder
Authors: Yabushita Y. , Brzoskowski R. , White J. L. , Najakima N. 
Published: December 2013

Abstract
A cold feed rubber extruder has been rebuilt into a pin barrel extruder with two rows of pins. A comparative experimental study has been made of the initial cold feed extruder, the extruder with a screw with slices in two flights, and the extruder with pins as well as Slight slices. An experimental study of pumping characteristics (Q – Δp screw curves) and of flow patterns obtained from feeding black and white compound with curatives to the extruder with subsequent vulcanization after steady state is achieved. Longitudinal and transverse sections of the rubber compound cured in the flights are studied. It is shown that introducing slices into screw flights reduces pumping capability. The subsequent introduction of pins has little effect on pumping. The flow marker studies show that introduction of slices into screw flights significantly enhances mixing. Both the improved mixing and poorer pumping is due to backflow through the slices. The introduction of pins is shown to again greatly increase mixing. The results of this study are used to discuss the performance and design of commercial pin barrel extruders for the rubber industry.
Mixing, Devolatilization, and Reactive Processing in the a Farrel Continuous Mixer**
Authors: Valsamis L. N. , Canedo E. L. 
Published: December 2013

Abstract
The Farrel Continuous Mixer, developed in the late 50s and introduced to the market in the early 60s, has been extensively used in plastics and rubber mixing and compounding for several decades, and has undergone several design changes and refinements. This paper reviews and discusses in detail the unique mixing characteristics of the FCM. Recent developments in rotor design for controlled residence time and processing temperatures, sequential incorporation of additives, post-reactor reactive processing, and improved energy efficiency by means of total process control are presented. Flow patterns inside the mixer are established using freezing and tracer techniques. Mathematical models for mixing and devolatilization are developed and verified with pilot plant data. As an example of reactive processing, data on the vis breaking of polypropylene with organic peroxides are presented. Controlled rheology of the polymer is achieved and undesirable volatile by-products, tert-butyl alcohol in the present case, are effectively vented. Experimental residence time distribution, and calculated passage and maximum shear rate distribution functions are also presented and discussed.
Investigations of the Residence Time and the Longitudinal Mixing Behavior in Counter-rotating Twin Screw Extruders
Authors: Potente H. , Schultheis S. M. 
Published: December 2013

Abstract
This paper presents a distribution function which allows to calculate the residence time distribution in a counter rotating twin screw extruder. Only the minimum and mean residence time appear in this function. The agreement between calculated and experimentally determined residence times is satisfactory. Longitudinal mixing capacity is discribed with the aid of the residence time variance.
Single and Double Bubble Tubular Film Extrusion of Polyethylene Terephthalate
Authors: Kang H. J. , White J. L. , Cakmak M. 
Published: December 2013

Abstract
An experimental study of double bubble tubular film extrusion of polyethylene terephthalate is presented. In the second bubble, the film is passed through a hot air where it undergoes a significant increase in inflation level. The mechanical stability of both bubbles is investigated as a function of process conditions. The film produced by the first bubble is largely amorphous/glassy (5 to 7%, crystallinity), while that produced in the second bubble can have significant levels of crystallinity (7 to 45 %) dependent upon process conditions. Crystallinity notably increases with machine direction draw down ratio. The crystallinity levels are similar to those of biaxially stretched films. Subsequent annealing increases and perfects crystallinity. The surface roughness of double bubble tubular films is similar to that of glassy polymers produced from single bubble operations and is much less than for polyolefins. The orientation in the films has been determined by (i) wide angle x-ray diffraction applying both pole figure analysis and biaxial orientation factors (ii) measurement of in-plane and out-of-plane birefringence. Biaxiality of orientation increases with the second blowup ratio. The mechanical properties of the film were determined as a function of angle in the plane of the film.
Dynamics of a High Speed Melter/Mixer
Authors: Lyons D. , Baker W. E. 
Published: December 2013

Abstract
A first attempt at studying the internal dynamics of the Gelimat high shear polymer melter/mixer has been made, using slow motion photography of the inside of the fluxing chamber of the device during operation. Based upon these observations, a satisfactory mathematical model has been developed for the melting process which incorporates an energy balance and energy dissipation resulting from drag flow through a fluid bed. This model is a first step towards a more complete and rigorous theoretical treatment of the device, and allows for the prediciton of the time to melt a powdered polymer based on angular velocity of the mixing paddles, mixer geometry, polymer charge size, desired discharge temperature and the thermal properties of the polymer.
Further Considerations of Simulation of Flow in Pin Barrel Extruders and in Screw Extruders with Sliced Flights
Authors: Brzoskowski R. , White J. L. 
Published: December 2013

Abstract
The flow and pumping capability of extruder screws with slices in their flights and pin barrel extruders have been modelled with special consideration on its single or multi-flighted character and the periodicity of the positions of the slices and rows of pins. This is done using an analytical method developed by the authors. The method of analysis is extended to non-Newtonian fluids.