bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generalized Predictive Observer-Controller For Injection Moulding
Authors: Huang S. N. , Tan K. K. , Lee T. H. 
Published: December 2013

Abstract
In this paper, a generalized predictive observer-controller (GPOC) is developed for injection moulding with input delay and non-measurable states. First, based on a general state-space model with time delay and subject to process disturbances, a generalized predictive control (GPC) is appropriately formulated with a steady-state Kalman filter. Second, important and useful closed-loop characteristics relating to the stability and robustness of the proposed controller are provided. Finally, the proposed scheme is applied to the injection moulding to improve the control performance.
Fiber Orientation in 3-D Injection Molded Features
Authors: VerWeyst B. E. , Tucker C. L. , Foss P. H. , O'Gara J. F. 
Published: December 2013

Abstract
We present a finite element method for predicting the fiber orientation patterns in 3-D injection molded features, and compare the predictions to experiments. The predictions solve the full balance equations of mass, momentum, and energy for a generalized Newtonian fluid. A second-order tensor is used to describe and calculate the local fiber orientation state. A standard Hele-Shaw molding filling simulation is used to provide inlet boundary conditions for the detailed inite element models, which are limited to the local geometry of each feature. The experiments use automated image analysis of polished cross-sections to determine fiber orientation as a function of position. Predictions compare well with experiments on a transverse rib, where the detailed calculation can be 2-D. Results of a 3-D calculation for a flow-direction rib also show generally good agreement with experiments. Some errors in this latter calculation are caused by not simulating the initial filling of the rib, due to computational limits.
Polymer Solidification under Pressure and High Cooling Rates
Authors: Brucato V. , Carrubba V. La , Piccarolo S. , Titomanlio G. 
Published: December 2013

Abstract
Polymer solidification under processing conditions is a complex phenomenon in which the kinetics of flow, high thermal gradients and high pressures determine the product morphology. The study of polymer structure formed under pressure has been mainly made using conventional techniques such as dilatometry and differential scanning calorimetry under isothermal conditions or non isothermal conditions but at cooling rates several orders of magnitude lower than those experienced in industrial processes. A new equipment has been recently developed and improved to study the crystallization of polypropylene when subjected to pressure and cooled rapidly. An experimental apparatus essentially constituted of a special injection mould has been employed. Polymer samples can be cooled at a known cooling rate and under a known pressure. Micro Hardness (MH), Wide angle x-ray diffraction (WAXD), Polarised Optical Microscopy (POM) and density measurements are then used to characterize the sample morphology. The results of rapid cooling experiments under pressure on an iPP sample display a lower density and a lower density dependence on cooling rate for increasing pressure. Micro hardness confirms the trend.
A deconvolution technique of WAXD patterns is used to evaluate the final phase content of samples and to assess a crystallization kinetics behaviour. Phase distribution results indicate that the decrease of alpha phase with pressure is balanced by an increase of the mesomorphic phase leaving unaffected the amorphous phase content. This peculiar behaviour can be easily related to a negative influence of pressure on the kinetics of the crystallization of alpha phase.
Computer Aided Optimisation of Profile Extrusion Dies
Authors: Szarvasy I. , Sienz J. , Pittman J. F. T. , Hinton E. 
Published: December 2013

Abstract
An objective function is proposed for use in optimisation of profile die design, and defined in terms of mass flow rates to topological partitions of the profile cross section. In a series of uPVC extrusion trials its dependence on land channel height is investigated for two profiles to assess its suitability for gradient based optimisation of flow distribution. Preliminary finite element flow simulations are carried out, and comparisons of computed and experimental objective function values show that the mathematical modelling should be extended to include extensional effects and draw down at the die exit. Examination of the experimental profiles indicates the limitations of die optimisation in determining the detailed geometry of the finished profile cross sections.
Polymer Blends with Fibrillar Phase Morphology Prepared by Self-Reinforcing Technique
Authors: Varga J. , Breining A. , Ehrenstein G. W. 
Published: December 2013

Abstract
High-strength, high-modulus products with a characteristic phase morphology were prepared via the injection molding of blends of isotactic polypropylene (PP) and polyamide-12 (PA-12) under special processing conditions (low melt temperature, high holding pressure, and a convergent sprue design). These conditions generated a situation in which the dispersed phase can be distributed in the self-reinforced matrix as oriented fibrils. Optical (polarized light optical and phase contrast) microscopic and SEM investigations revealed a uniform distribution of the dispersed phase within the matrix. These products can be regarded as in situ thermoplastic composites. The strength level of the self-reinforced blends is approximately twice as high as that of the products processed under conventional conditions. The PA-12 phase dispersed as ultrathin fibrils enhances the flexural impact strength of the blends, decreases their notch sensitivity, and alters its fracture mechanism.
Factors Affecting the Stability of Gas Penetration in Gas Assist Injection Molded Bifurcation Parts
Authors: Liu S.-J. , Wu Y.-C. 
Published: December 2013

Abstract
Gas assist injection molding has become an increasingly important process in industry because of its tremendous flexibility in the design and manufacture of plastic parts. However there are some unsolved problems that confound the overall success of this technique. Unstable gas penetration in molded bifurcation parts caused by inappropriate mold/part designs and processing conditions is one of them. This report was to study the gas penetration behavior in gas assist injection molded bifurcation parts. Experiments were carried out on an 80-ton injection molding machine equipped with a high pressure nitrogen-gas injection unit. A bifurcation cavity with a part thickness of 20 mm was used for all experiments. The resin used was general purpose polystyrene to help visualize the gas penetration behavior in the parts. Various processing variables were studied in terms of their influence on the stability of gas penetration in the parts: gate position, mold layout, melt temperature, mold temperature, short shot size, gas pressure and gas injection delay time. The purpose of this study was to investigate the parameters affecting the stability of gas penetration, so that steps can be taken to optimize the gas penetration behavior. This would provide significant advantages in improving product quality.
Investigation of Structure and Properties in Biaxially Stretched Poly(butylene terephthalate) Films
Authors: Song K.-J. , White J.L. 
Published: December 2013

Abstract
Effects of deformation history on the development of structure and properties in biaxially stretched poly(butylene terephthalate) (PBT) films are described. PBT cast films are stretched at two temperatures: 65°C and 90°C, with varying draw ratios. The refractometer and X-ray scattering techniques characterize the resultant films. As-stretched films have crystals of small sizes, in which the α crystals are appreciably larger and oriented more than the β phase. Films that are stretched at the low temperature, on the other hand, exhibit higher orientations of both the overall and amorphous chains. Annealing of the films under constraint causes the crystalline phase to undergo perfection and transition. A model of crystalline morphology is presented which describes the mechanical anisotropy present in biaxially oriented PBT films.
In-Process R eometry Studies of LDPE Compounds
Authors: Kelly A.L. , Woodhead M. , Coates P.D. , Barnwell D. , Martin K. 
Published: December 2013

Abstract
The initial part of a comprehensive study into the investigation and validation of in-process measurements on a low density polyethylene (LDPE) compound during extrusion is reported. An unfilled, commercial grade of low density polyethylene was processed using fully instrumented, computer monitored, single and twin screw extruders in the Interdisciplinary Research Centre (IRC) laboratories, University of Bradford. Three in-process rheometers were used; a prototype Rosand capillary on-line rheometer (OLR), a four sensor slit die in-line rheometer (ILR) and a six sensor slit die ILR. Off-line comparisons were carried out using a Rosand RH twin bore capillary rheometer. All devices allowed shear ow characterisation at a range of processing rates, and the capillary rheometers also provided a measurement of entry pressure drop through the use of orifice dies. The six-sensor ILR also allowed measurement of entry pressure drop into the slit, although the differences in ow geometry meant these measurements were not directly comparable with the capillary devices, and exit pressures were extrapolated from ILR pressure drops. The in-process devices exhibited very good agreement with measurements made off-line, in both shear ow and entry pressures. In-line slit die measurements were very close to those made using capillary dies, despite the in-line tests being non-isothermal and employing a different geometry of measurement section. Differences in melt rheology between single and twin extrusion were observed, due to the amount of mechanical work input by each extruder. Overall, good agreement was observed from the four different routes to measurement, for the LDPE examined.
In-Line Density Monitoring of Rigid PVC Foam during Extrusion Process
Authors: Abu-Zahra N. H. , Chang H. 
Published: December 2013

Abstract
An ultrasound-based sensor has been investigated to monitor the density of rigid PVC foam, in-line, during the extrusion process. A 2.25 MHz ultrasound transducer was used to measure the acoustic properties; i.e. speed of sound, acoustic impedance, and attenuation, in the polymer melt prior to exiting the extrusion die. A special transducer adapter and wave re ector were incorporated in the design of the extrusion die. The density of PVC foam was varied by varying the blowing agent content in the resin compound prior to extrusion. A mathematical derivation of the behavior of ultrasound waves in the melt is presented and used to calculate the attenuation coefficient of the polymer melt at various foam densities. An empirical relation was derived between the calculated attenuation coefficient of the polymer melt and the measured density of the foam extrudate. This relation can be used to estimate the foam density based on the acoustic measurement of the melt in the extrusion die. Further work is proposed to normalize for the effect of variations in the melt temperature and pressure on the ultrasound measurements.
Development of a Direct Polycondensation Process for Poly (L-lactic acid)
Authors: Fukushima T. , Sumihiro Y. , Koyanagi K. , Hashimoto N. , Kimura Y. , Sakai T. 
Published: December 2013

Abstract
Poly(L-lactic acid) (PLLA) is quite promising for use as biodegradable and non-petroleum derived plastics. In this study we developed an innovative two-step polycondensation process so as to produce economically PLLA with high molecular weight. The process is composed of both melt polycondensation under the lactide-re ux and solid-phase polycondensation. First we studied a direct polycondensation of L-lactic acid with a small amount of solvent, using a mixture of L-lactic acid as raw material, diphenyl ether as solvent, Tin (II) chloride dihydrate as catalyst, and p-toluene sulfonic acid as a discoloration prevention agent. After the dehydrative oligomerization of L-lactic acid, the polycondensation of the oligocondensates and solid-phase post-polycondensation, PLLA of Mw = 266,000 could be obtained. Then, we carried out direct bulk polycondensation tests from L-lactic acid without any solvent added. After optimization of the reaction conditions, PLLA with Mw = 134,000 was successfully produced by the melt-poly-condensation of L-lactic acid accompanied by solid-phase post-poly-condensation. In both systems, the lactide-re ux was indispensable for promoting dehydration/water removal. The re uent lactide was taken into the polymer-chain by trans-esterification reaction during the melt-poly-condesation. Furthermore, the catalyst was allowed to deactivate and stabilize during the solid-phase polymerization to cause the Mw growth.
Tight Tolerance Thermoforming
Authors: Xu H. , Kazmer D. O. 
Published: December 2013

Abstract
Tighter tolerances are becoming more prevalent as thermoforming applications are increasingly utilized in multiple component assemblies with load bearing and other functional capabilities. A1 analytical method is described for shrinkage predictions utilizing a thermoviscoelastic constitutive model to try and avoid costly and time consuming forming trials by determine adequacy of the mold and process a-priori. Validation experiments and sensitivity analyses were performed to understand the process behavior and estimate the accuracy of the shrinkage analysis. Design and manufacturing guidelines were then developed to facilitate tight tolerance thermoforming. While the analysis was generally capable of predicting linear shrinkage, statistical yield models indicated that improved process control and further process development is required to consistently produce thermoformed parts to tight tolerances.
Melting of Polymer Blends in Co-rotating Twin Screw Extruders
Authors: Bastian M. 
Published: December 2013

Abstract
The properties of polymer blends are conditioned to a large extent by the morphological structure of the polymer combinations employed. Since the development of the morphology inside the extruder is essentially influenced by the melting section, it is necessary to be able to estimate the melting process of binary material combinations. Part I of this publication summarises the knowledge that has been acquired in theoretical and experimental studies of melting in co-rotating, tightly-intermeshing twin screw extruders. The experimental studies reveal quite dissimilar melting mechanisms for different materials in some cases. Different models are thus available for calculating the melting process of single-component materials which have been developed on the basis of the findings established in experimental investigations. Only one model is so far familiar for the melting process of multi-material systems. This uses material values for polymer blends that have been averaged out with mixing rules to provide the basis for a calculation to estimate the melting process.
Part II of the publication describes a model for calculating the melting of binary, incompatible polymer combinations which has been implemented in the SIGMA simulation software for the design of co-rotating twin screw extruders. This model can be used to calculate the temperature development in the solids conveying section and the subsequent melting process.
Part III of the publication explains one possible means of investigating the melting of binary polymer combinations and discusses the results of experimental studies of polypropylene/polyamide blends. For purposes of verifying the model set out in this part of the publication, the simulation calculations are compared with the results of the experimental studies.
The “New-Generation” Co-flow Intermeshing Internal Mixer
Authors: Nortey N. O. 
Published: December 2013

Abstract
The “new-generation” Coflow4™ intermeshing internal mixer uses less motor power peak and specific energy than all traditional intermeshing and tangential internal mixers. The Co-flow4™ mixer provides the following advantages: better quality, 20% to 45% increase in productivity depending on your rotor length-to-diameter ratio, improved heat transfer, over 50% reduction in dust-stop leaks, better for one-pass or multiple-pass mixing, wide range of process materials, better wear life, retrofit capabilities and lower mixer cost. It is more cost effective to retrofit your traditional mixer with a Coflow4™ mixer when your chamber bores and rotors are worn out, and you are ready for a rebuild rather than investing into the same old mixing technologies that yield small return. Owing to the optimal constant rotor length-to-diameter ratio and the superior mixing capabilities of the co-flow mixing technology, it will be beneficial to try and use the Coflow4™ mixer to compound the materials, which could not be compounded before by the old traditional mixing technologies or the two-roll mills.
Injection Molding Technology for High Speed Optical Disk
Authors: Park S. J. , Kim S. K. , Yoon K. H. , Kwon T. H. 
Published: December 2013

Abstract
Recently great efforts have been made to increase the data access speed and the data storage density of the optical memory disks such as CD-ROM, DVD, ASMO disk, etc. In the viewpoint of increasing the data access speed of the optical disks, it is of great importance to characterize accurately the vibration phenomena of the rotating disk, which is related to the critical speed and the characteristics of the frequency response. In this paper, towards the goal of increasing the data access speed of the optical disks, we have proposed a novel method for improved characteristics of disk vibration without deteriorating any other specification for the optical memory disks such as geometrical and optical characteristics. A possible idea to improve the vibration characteristics of the optical disk is that the tensile initial stress in the radial direction is to be imposed within the optical disk on purpose. By the synergy effect from the residual (initial) tensile stress frozen within the optical disk combined with the stress induced by the centrifugal force occurring in rotating the optical disk, the stiffness of the disk would increase to have a stronger resistance to the disturbance resulting in increase of critical speed. With such a synergy effect in mind, modifications related to the optical disk substrate design, injection mold design and processing conditions of injection molding were presented and partially evaluated. The computer simulation and experiments indicate that the suggested ideas clearly improve the characteristics of disk vibration without deteriorating any other specification for the optical memory disks.
Experimental Study of Melting in an Intermeshing Counter-Rotating Twin Screw Extruder
Authors: Wilczynski K. , White J. L. 
Published: December 2013

Abstract
An experimental study is presented of the melting mechanism in a starve fed closely intermeshing counter-rotating twin screw extruder of a modular Leistritz design. Polypropylene and low density polyethylene as well as different screw configurations of thick flighted and thin flighted elements were investigated, at various operating conditions. A “Screw Pulling-out Technique” was used to characterize polymer behavior along the screw axis. In particular, the solid conveying, melting positions, the extent of starved character along the screw, and the fully filled regions were observed. Polymer samples were stripped off from each screw which was removed from the machine to investigate melting mechanism. Generally, it was concluded that the melt mechanism consists of pellets being dragged into the calendering gap where they are melted due to calendering action. In the case of thick flighted screws, the molten polymer is expelled from the gap and pushes against the pellet bed which is continuously dragged into the gap.
The Design of Extrusion Screws: An Optimization Approach
Authors: Gaspar-Cunha A. , Covas J. A. 
Published: December 2013

Abstract
The design of a screw for plasticating polymer extrusion based on scientific principles is still a challenging task, which has received surprisingly little attention in the literature. In the present work the design of a screw is considered as an optimization problem. The corresponding design methodology is discussed. Two alternative approaches are considered. In the first case, the aim is to maximize the value of an objective function that describes quantitatively the process performance in terms of pre-selected important process criteria. A multiobjective optimization scheme resorting to the use of optimal or non-dominated Pareto frontiers is also implemented, where the set of feasible individual solutions in terms of the various criteria is correlated, thus evidencing the compromise between them. The relevance of the solutions and the sensitivity of the method to changes in the criteria considered are demonstrated with a case study.
Computational Study of the Velocity Field in the Conveying Element of a Ko-kneader with CFD Method
Authors: Mehranpour M. , Nazokdast H. , Dabir B. 
Published: December 2013

Abstract
An attempt has been made to predict the velocity field in the conveying element of a Ko-Kneader using CFD method. The effects of both rotating and reciprocating motions of the screw have been taken in to account in three dimensional flow analysis. It has been demonstrated that such computational method can provide a great insight into visualization of the flow field in this element of a Ko-Kneader. Among the variables the reciprocating action was found to play a significant role on enhancing the mixing performance of the Ko-Kneader by means of periodical changing the flow field and shear rate distribution in the channel.
Preferable Filament Diameter Ratios of Hybrid Yarn Components for Optimized Longfiber Reinforced Thermoplastics
Authors: Beyreuther R. , Brünig H. , Vogel R. 
Published: December 2013

Abstract
The mechanical properties of hybrid (commingled) yarn based reinforced thermoplastics depend on many parameters of the fiber components as well as of the different technological conditions during the commingling and the hot press molding. Among the fiber parameters the diameter ratio of the matrix and the reinforcing yarn components are most important to obtain best mechanical properties of the reinforced thermoplastics. The paper treats theoretical considerations in order to reach a high probability of coating each reinforcing filament with the thermoplastic material during the hot press molding. The calculations include the filament ratios and the achieved volume ratios of both hybrid yarn components of the finished reinforced thermoplastics. It is demonstrated that under different optimization criterias (same filament numbers for both components or the same surfaces of the reinforcing yarn filaments and the matrix yarn filaments before the hot press molding) a more or less small range of filament ratios seem to be valid for manufacturing a homogeneous faultless reinforced thermoplastic. Quantitative calculations for two hybrid yarn systems PEEK/carbon fibers and PP/glass fibers, presented in diagrams, are demonstrated. Technological conditions for the spinning of micro fibers like PEEK-filaments complete the presentation.