bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Principles Governing the Design of Barrier Sections in Extruders
Authors: Potente H. , Stenzel H. 
Published: December 2013

Abstract
Barrier screws used in conjunction with grooved-barrel extruders are gaining increasing importance on account of their high throughput and melting performance as well as their good homogenizing action. Although a number of calculation formulae now exist for the barrier screw, no comprehensive, logical design system for power law melts has been compiled to date. This paper takes a simple melting model and shows how the geometry of the barrier section can be designed (flight depth and screw channel width of the channels for the solid and the molten material and the length of the barrier section). A method of calculating the pressure and temperature profile in the melt channel is also presented. The different variables affecting the melting process are discussed on the basis of parameter studies.
New Ways in the Manufacturing of Finished and Semi-finished Products from Nylon
Authors: Michaeli W. , Berghaus U. , Speuser G. 
Published: December 2013

Abstract
In conventional processing, extruders have been used, mainly, for continuous compounding and processing of polymers. Yet, for a long time they have been serving as chemical reactors. It has been 50 years since first developments were made in the field of extruder application as a reactor. In the following, we will offer the reader a review of research and development activities of the Institut für Kunststoffverarbeitung (IKV) in the field of reactive extrusion.
Flow-Induced Crystallization and Self-Reinforcement During Extrusion
Authors: McHugh A. J. , Tree D. A. , Pornnimit B. , Ehrenstein G. W. 
Published: December 2013

Abstract
Flow-induced crystallization of high-density polyethylene and polypropylene films has been studied in a slit die equipped with optical windows to allow direct visual observation of the process. Mechanical and thermal property measurements and morphological analyses verify the presence of self-reinforced, extended-chain structures in the extrudate. By controlling the location of the crystallization front inside the die but near the exit, continuous extrusion was possible at lower pressures than previously reported. Birefringence measurements of the melt flow indicated the feasibility of an optimal die geometry to maximize oriented structure development during continuous extrusion while minimizing pressure buildup.
Closed Loop Control of Parison Dimension Profiles in Extrusion Blow Molding
Authors: DiRaddo R. W. , Patterson W. I. , Kamal M. R. 
Published: December 2013

Abstract
Extrusion blow molding is utilized in the production of plastic hollow containers. One of the critical steps in the process sequence is the formation of an annular extrudate, called the parison. Extrusion of the parison through an annular die is associated with varying degrees of swell and sag along the length. Moreover, the design of many commercial blow molding products requires variations in wall thickness along the length of the parison. The present work describes the design and operation of an on-line computerized parison thickness profile measurement technique for the purpose of implementing closed loop control of the parison thickness profile.
The proposed thickness measurement technique was evaluated by comparing it to the conventional pinch-off mold technique. The control strategy employed involves a simple on-line adaptive control scheme. Programmed set point profiles, such as constant, linear and oscillatory profiles were implemented to within a 5% error. Moreover, the adaptive controller compensates for system disturbances.
Existing Scale-up Rules for Single-screw Plasticating Extruders
Authors: Potente H. 
Published: December 2013

Abstract
This paper gives a review of existing scale-up rules for single screw plasticating extruders. It is shown that there were and still are rather varied trends. The main three are:

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scale-up rules under the boundary conditions of an invariant shear rate,

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scale-up rules including the power law,

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scale-up rules including the zones of operation.

In Europe, at least, the scale-up rules, which take the power law-flow characteristics into account, seem to have been established in practical terms. For economical reasons conventional extruders are designed in such a way, that the output increases with the square of the diameter. This however, results in the problem that the melting rate does not follow the same scale-up rules as the pumping rate and the solid conveying rate. Thus the discussion continues, to calculate the operating section lengths according to varying scale-up rules. Finally the scale-up problem is discussed once more with respect to the dominant dimensionless numbers, and despite several similarity theoretical difficulties a standardized solution will be attempted to be found.
Mechanical Properties of Thermoplastic Polyurethane Blends and Copolymers of Styrene and Acrylonitrile
Authors: Žerjal B. , Musil V. , Jelčić Ž. , Šmit I. , Malavašić T. 
Published: December 2013

Abstract
Mechanical data obtained on the blends described in a previous paper together with some new data have been correlated with the theory derived for the mechanical properties of polymer composites, to gain insight into the nature of domain interfaces. Thermoplastic polyurethanes are blended in the entire composition range, with styrene-acrylonitrile copolymers. Blending with thermoplastic polyurethanes improves the toughness. Improved toughness is indicated by the increase of elongation at break and by decrease of hardness.
Mixing on Melting in Single Screw Extrusion
Authors: Benkreira H. , Shales R. W. , Edwards M. F. 
Published: December 2013

Abstract
A new approach to assessing mixing in single screw plasticating extruders is proposed. It is based on image analysis of microtomed sections obtained from the polymer helix formed in a suddenly cooled split barrel extruder fed with a mixture of black and white polymer granules. The observations suggest that most of the mixing occurs on melting with little improvement thereafter. A simple laminar mixing model is drawn in the melting zone the results of which compare favourably with experimental data. In particular, it is shown that improved mixing can be achieved with increasing screw speed in complete contradiction with the classical strain theories which consider mixing in the melt conveying zone only.
Simulation of 3-Dimensional Flow in Internal Mixers
Authors: Hu B. , White J. L. 
Published: December 2013

Abstract
The design of internal mixers for the rubber industry has traditionally been based on the basis of intuition rather than a knowledge of the fluid mechanics of motions in the internal mixer. In recent years, efforts have been made to numerically simulate the flow and mixing characteristics in internal mixers. The simulation effort is important for the understanding of mixing mechanisms in the internal mixer, and furthermore, to provide a basis for rational design. In this paper, we develop a new model based on cylindrical coordinate hydrodynamic lubrication theory for internal mixers. This allows full consideration of curvature in an internal mixer. Numerical techniques are used to carry out the calculations of the pressure field and flux field for various rotors described in the patent literature. This is done for a Newtonian fluid in a fully filled mixing chamber. This type of calculation is of key importance in the design of flight arrangements on internal mixer rotors.
Maleation of Polypropylene Melt in Model Reactors
Authors: Polance R. , Jayaraman K. 
Published: December 2013

Abstract
The maleation of polypropylene melt with a peroxide as free radical initiator has been carried out isothermally in a continuous flow reactor and in a batch flow reactor. The continuous flow reactor is designed to provide significant levels of extensional strain in the fluid while the batch flow reactor provides a simple shear flow with uniform residence time. In both reactors, less than 1 part per hundred of dicumyl peroxide (dissolved in xylene) is added to a preblended single phase mixture of polymer melt and dibutyl maleate. The relative extent of maleation is much higher in the continuous flow reactor than in the batch reactor with comparable shear strain rates and mean residence times. As the feed rate and the rotation speed are varied at a fixed temperature in the continuous flow reactor, the highest degree of maleation is obtained under conditions where fluid dynamics computations show the stretching of a fluid element to be the greatest. Hence, increasing shear alone leads to rather limited increases in extent of maleation. These results emphasize the importance of the detailed deformation field for carrying out functionalization reactions on polymer melts.
Melting of Plastics in Kneading Blocks
Authors: Todd D. B. 
Published: December 2013

Abstract
Melting of plastics in intermeshing co-rotating twin screw extruders is known to occur over very short barrel lengths. The melting phenomenon has been studied for both pellets and powder in a readily opened clam shell barrel. The melting mechanism is attributed mainly to the dissipation of the energy imparted in interparticle friction as a consequence of the unique kneading action of this type extruder.
Dynamics and Control of Surface and Mold Temperatures in Injection Molding
Authors: Gao F. , Patterson W. I. , Kamal M. R. 
Published: December 2013

Abstract
Mold temperature control in injection molding is very important for control of production rate and product quality. However, mold temperature is a complex function of machine design, process variables, machine settings and ambient conditions. Data were obtained regarding the variability in both space and time (in-cycle and cycle-to-cycle) of mold metal and mold surface temperatures and heat flux. In view of this variability, it is necessary to define variables which may be useful for control purposes. The following variables were evaluated: cycle average temperature, peak temperature, and partial cooling time. Dynamic models were developed, on the basis of experimental data, to determine the process gains, time constants and time delays for the above variables with regard to coolant temperature, coolant flowrate, and melt temperature as the possible manipulated variables. In view of the dynamic studies, the cycle average surface temperature was selected as the controlled variable for control system design and simulation. The regulating abilities of PI, PID, and Dahlin controllers were evaluated. The results indicate that Dahlin control caused the controlled variable to follow the set-point closely, even when the process parameters vary, thus showing good robustness. However, the Dahlin algorithm achieves this advantage via large variations in the manipulated variable. This may cause difficulty in some circumstances.
Detailed Investigations of Structural Layering Phenomena in Injection Molded Thermotropic LCP
Authors: Hsiung C. M. , Tian J. , Cakmak M. 
Published: December 2013

Abstract
Effects of processing variables on the structural gradients developed in the injection molding of thermotropic wholly aromatic copolyester parts were investigated using optical macro and microscopy combined with image analysis techniques at various sections of the molded LCP parts.
The studies indicate the existence of a multi-layer structure from skin to core of the parts. These include: a skin layer, a transition zone composed of a sub-skin layer, a shear layer and a core region. The effects of processing conditions including injection speed, mold temperature, and mold size on the structural features were evaluated. An interesting buckling phenomenon resembling features observed in jetting at core regions near the end of the cavity after the divergence section was observed for the samples molded at the lowest injection speed and mold temperature.
Digital image analysis of the images of the sectioned parts revealed that there are more layers than one observes macroscopically. In certain instances as many as 15 layers were detected. Orientation behavior and the positional light reflection intensity appear to correlate with each other particularly away from the skin regions. This may be the manifestation of high visible light absorption anisotropy exhibited by these aromatic polymers.
Computer Controlled Rotational Molding of Liquid Silicone Polymer
Authors: Teoh S. H. , Guan K. W. , Lee N. H. , Wong Y. S. , Nee A. Y. C. , Pho R. W. H. 
Published: December 2013

Abstract
Rotational molding in two axes has the advantage of producing hollow products. Previously, the inherent difficulty was in the production of objects with uniform thickness since the speed of the two primary axes are fixed and cannot be varied independently to take into account the changes in material properties such as its density and viscosity. With the advent of computers, it is now possible to control the thickness of the object accurately. This is made possible by creating an intelligent software which takes in the viscosity and density time variation of the polymer and using the flat plate withdrawal theory, computes the new speed for each axis. The relationship between rotational molding parameters and polymeric material properties for a solvent – silicone rubber system to produce a hand prosthesis is illustrated in this paper.
A Unified View of Modeling Flow in Counter-rotating Twin Screw Extruders
Authors: White J. L. , Adewale A. O. 
Published: December 2013

Abstract
Intermeshing counter-rotating twin screw extruders have played an important role in polymer processing technology in the post World War II period. They operate on basically the same principle as low viscosity multiple screw pumps, i.e. they involve forward pumping of fluid contained in C-chambers, which are regions between the screw root and barrel between the interlocked intermeshing regions. Tangential counter-rotating twin screw extruders with open screw channels have also been manufactured in the same period. A new more general model of flow of a Newtonian fluid in a counter-rotating twin screw extruder with partially intermeshing screws is presented. The model allows transition from fully intermeshing to tangential screw machine systems. Calculations are made to show the effect of level of intermesh on pumping capability. Modular counter-rotating twin screw machines are analyzed. The problem of starvation is discussed.
Simulation of Injection Molding and Comparison with Experimental Values
Authors: Potente H. , Schulte H. , Effen N. 
Published: December 2013

Abstract
The outstanding economic importance of injection molding in plastics processing and the steadily growing requirements on the molded parts to be produced are leading to constant further developments in the process engineering for injection molding. Computer simulation is a method that has only recently come to be used to an increasing extent in the field of injection molding, and the use of computers has so far been restricted to simulation of the injection mold. One key prerequisite for the quality of the molded parts, however, is that the melt should have been prepared by the plasticating unit in a manner that comes as close to the ideal as possible.
The article presents a closed basis for calculation for the simulation of the plasticisation process in injection molding. This makes it possible for a large number of screw layout criteria to be estimated and calculated in advance. The computer simulation serves to make the plasticisation process more or less transparent and also clearer and calculable. The validity of the computation model for any size of plasticating units is demonstrated by examining the operating points of large industrial plants.
Two-Dimensional Dynamic Study of the Distributive Mixing in an Internal Mixer
Authors: Wong Tang H. , Manas-Zloczower Ica 
Published: December 2013

Abstract
Distributive mixing in an internal mixer was studied numerically by means of tracking the evolution of the distance between pairs of particles in the mixing chamber. The distributions of these pairwise distances are reported in terms of the probability density function of a pairwise correlation function. In conjunction with this descriptive technique, a dynamic particle-tracking algorithm for two dimensions has been developed to study the dynamics of mixing in the mixer. We also propose a parameter e to monitor the extent of mixing. This general approach represents the first attempt of this kind to address directly the goodness of mixing. A total of five operating modes was considered. Three of them have even speed ratio of 60 rpm and rotors positioned at 90–90, 90–180, 90–270 relative to the horizontal axis, respectively. The remaining two have uneven speed of 60 rpm/40 rpm and rotors positioned at 90–90, 90–270 relative to the horizontal axis, respectively. For each operating mode, a complete period is represented as a sequence of snap shots (72 for even speed and 216 for uneven speed) and the flow field for each snap shot was calculated by means of FIDAP. Based on our proposed framework, we were able to demonstrate clearly that the anti-symmetric configuration (90–270) is the best operating mode among the three even speed cases and the configuration (90–180) is the worst. The performance of the uneven speed cases fell in between the even speed cases.
3-D Flow Simulations of a Cavity Transfer Mixer
Authors: Wang C. , Manas-Zloczower I. 
Published: December 2013

Abstract
The Cavity Transfer Mixer (CTM) was primarily designed as a distributive mixing device to be used as an add-on unit to existing extruders. In determining the CTM overall mixing efficiency as well as its potential use for various applications, the flow patterns/characteristics within this mixer must be well understood. In this work, a fluid dynamics analysis package – FIDAP – using the finite element method was employed to simulate the flow patterns in a CTM with 3 rows and 6 cavities per row. A 3-D, isothermal flow analysis for a Newtonian fluid was carried out. The flow field was characterized in terms of velocity profiles, average shear stresses and a parameter λ quantifying the elongational flow components. The influence of processing variables on the flow characteristics was also discussed. The simulation results show good agreement with the experimental data.
Orientation Evolution in Convergent-Divergent Dies
Authors: Zhao J. , Mascia L. 
Published: December 2013

Abstract
Solid-state extrusion experiments were carried out through constant area convergent-divergent dies using two crystalline polymers, i.e. ultra high molecular weight polyethylene (UHMWPE) and polytetrafluorethylene (PTFE), with the aim of producing extrudates exhibiting biaxial orientation. The evolution of orientation was examined along the extrusion axis by measuring the off-plane birefringence values at various distances from the entry on specimens removed from the dies. Simple analytical expressions relating orientation factor to draw ratio in the three mutually perpendicular directions were derived for crystalline polymers. These generalised relationships were found applicable for all types of deformations, i.e. monoaxial, biaxial and pure shear. On the basis of the data obtained and the predictions from the theoretical analysis, the deformations taking place in dies with small converging angles, known as fish-tail dies, were found to be close to a state of pure shear deformations, while dies with high converging angles initially, then changing to high divergencies in the second section, known as dual-taper dies, were found to give rise to a state of unbalanced biaxial deformations.
Equation of State for Pure Polymeric Fluids Theory Based on An Improved Hole and Cell Model
Authors: Wang N. H. , Sakai T. , Masuoka H. 
Published: December 2013

Abstract
A theoretical equation of state (EOS) for chain molecule fluids is presented based on an improved hole and cell model in which the geometries of both the cells and the mers are defined as the dodecahedrons and reasonably related with the Lennard-Jones potential. Furthermore the number of configurations is treated to contribute to the EOS by means of minimizing the Helmholtz free energy to determine the cell size. This study may be regarded as the improved theories about the hole and cell model proposed by Simha et al. and the hole model by Sanchez and Lacombe. The present EOS has three characteristic parameters per pure fluid, which can lead to a corresponding-state principle for pure polymeric fluids. The validity and applicability of the equation were investigated by correlating the experimental PVT data for some common polymers and predicting the thermal expansion coefficient and isothermal compressibility of PVAc.
Effect of the Cast Film Production Process on the Properties of Oriented Polypropylene Film
Authors: Peiffer H. , Dietz W. 
Published: December 2013

Abstract
To produce highly transparent flat film from polypropylene, the melt must be cooled as quickly as possible to form the cast film. With polypropylene, heat transfer in the cooling unit is associated with crystallization processes. These make it difficult to calculate cooling times and subsequently the geometry of the cooling unit. A mathematical method for designing cooling units for polypropylene melts is described. The calculated results are compared with experimental findings and recommendations for optimized cast film cooling are given.
The Optimisation of Masterbatch Formulations for Use in Single Screw Machines
Authors: Benkreira H. , Britton R. N. 
Published: December 2013

Abstract
Previous work by Benkreira et al. [1] has shown that the critical stage in distribution of additives in single screw extruders is the zone where the polymer melts; the subsequent pumping of the melt makes little difference to the mixture quality. It is suggested that the ideal masterbatch melts before the host polymer and coats each granule, while remaining sufficiently viscous to promote the shear heating and melting of the polymer. In order to test this hypothesis and quantify the requirements in terms of relative melting points and melt viscosities, a set of model masterbatches was produced and used for injection moulding at 1 % addition in a variety of polypropylenes and polyethylenes, but always under the same moulding conditions. Image analysis and “experts” judgement was used to rate the performance of these master-batches. The conclusions drawn from this work are that the designer of a masterbatch must consider the melting ranges of the masterbatch and its host polymer, and their relative viscosities in the temperature range of the forming process, in order to optimise the ease of distribution of the masterbatch.
An In-line Melt Rheometer for Molten Plastics
Authors: Nelson B. I. , Broadhead T. O. , Patterson W. I. , Dealy J. M. 
Published: December 2013

Abstract
An in-line rheometer designed for use as a sensor for closed-loop control of melt processing operations has been previously described. This instrument can measure the true viscosity of a melt stream over a range of shear rates. In order to evaluate its performance in processing applications the rheometer was mounted on a twin-screw extruder. A chemical degradation process was used to introduce changes in the molecular weight distribution, and thus the viscosity of a polypropylene resin, and these changes were monitored using the rheometer. For rapid replacement of melt in the zone of controlled shear in the rheometer, flow simulations indicated that it would be advantageous to operate the rheometer in a cyclic mode. A stochastic process identification technique based on a pseudorandom binary signal was used to determine the parameters of a first-order plus deadtime model of the process. In order to estimate the portion of the system response due to rheometer dynamics, residence time distributions were measured both with and without the rheometer present. It was found that the rheometer has a dead time of about 6's and a first order time constant of less than 15 s. The response of the new instrument is thus significantly faster than than that of melt process rheometers now commercially available.