bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Miscibility on Rheological and Mechanical Properties of PCL/SAN Blends
Authors: Keyzlarová L. , Sáha P.
Published: December 2013

Earlier, poly(∊-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) were found to be miscible on molecular level at 8 up to 28 wt.% of acrylonitrile (AN) in SAN copolymer [1]. The combination of PCL and different copolymers of SAN thus offers an opportunity to investigate the effect of miscibility on some key properties of the blends, e.g. rheological or mechanical. In this paper blends containing SAN with 25 wt.% of AN (miscible SAN-25) and 35 wt.% of AN (immiscible SAN-35) were used for this purpose.

Blends of PCL with various contents of SANs up to 40 wt.% were prepared by melt mixing in a Brabender laboratory mixer. The miscibility of the mixed PCL/SAN blends was investigated by differential scanning calorimetry (DSC). The blends rheological characteristics were determined on a Rheoflixer capillary rheometer at various temperatures. Rabinowitsch and Bagley corrections and the power-law relation were used. The extrudates were observed under a scanning electron microscope. In addition, mechanical testing was performed on a tensile testing machine.

It was found that blends of PCL with a minor amount of miscible SAN-25 provide a better balance of rheological and mechanical properties than those of pure PCL. The immiscible blend shows properties inferior to the miscible one. Immiscible SAN-35 increases viscosity, shear thinning and extrudate swell of PCL more than the miscible type. In contrast to the miscible blends containing SAN-25, which were without any form of unstable flow at shear rates of 10 to 10 000 s−1, melt fracture occurs in the immiscible blends with SAN-35. Positive synergism in tensile strength and elongation at break can be seen for 90/10 PCL/SAN-25 blend processed at 130°C. The addition up to 30 wt.% of SAN-25 miscible with PCL increases elongation at break.
Structuring of Interface-modified Polymer Blends
Authors: Lyngaae-Jørgensen J.
Published: December 2013

The paper treats the case where blends of polystyrene (PS), poly (dimethylsiloxane) (PDMS) and a diblock copolymer of PS and PDMS are used as model materials. This modelsystem is predicted to be “stable” in discrete blends in simple shear flow. Stable in the sence that the block copolymer can not be removed form the interface during simple shear flow.

A hypothesis stating that coalescence of drops may be subdued by “stable” diblock copolymer at the interfaces in 3D flows are tested with a Brabender mixing chamber. For well dispersed systems absence of coalescence would confine the occurrence of bicontinuous structures to a phase inversion point volume or prevent bicontinuous phase structure (IPS) formation all together.

Addition of PS-b-PDMS diblock copolymer do contract the volume fraction interval where IPS are found but a relatively broad interval is still observed. The phase inversion volume predicted by theory is outside the observed IPS interval for one of the investigated blend pairs.
Breakage and Buckling of Fibrous Reinforcements During Fabrication of Thermoplastic Matrix Composites
Authors: Cohen A. , Adams M. E. , Campbell G. A.
Published: December 2013

The paper addresses the buckling of fibrous reinforcements which occurs due to motion of the amorphous matrix material during solidification. The motion of the matrix material is caused by a variation in cooling rate in different portions of a composite while the sample is cooling. In the course of this study, samples were prepared with a fiber reinforcement sandwiched between premolded sheets of polycarbonate. Samples were either processed in a two-cavity, “dogbone” shape mold or in a rectangular, single-cavity mold matched die compression mold. In order to visualize the motion of the molten matrix material, strands of polycarbonate blended with carbon black were mounted into the matrix. The buckling behavior demonstrated sensitivity, to the amount of reinforcement observed with single and multiple filaments of carbon and Kevlar and bundles of carbon fiber tows. This paper provides scaling considerations indicating the sensitivity of the observed effects to processing conditions and concludes with a discussion of the implications for load carrying capabilities of composites.
Processing of Biodegradable Polymer Composites as A Drug Delivery System in Vitro
Authors: Liu S.-J. , Tsai C.-H. , Lin S.-S. , Ueng S. W.-N.
Published: December 2013

This report explores the alternative of processing biodegradable polymer-antibiotic composites as a long-term drug release. Polymer-antibiotic composite beads were manufactured by a compression-sintering technique. An elution method was employed to characterize the release rate of antibiotic over a 35-day period at 37°C. Biodegradable polymer composites released high concentrations of antibiotic (well above the breakpoint sensitivity concentration) in vitro for the period of time needed to treat bone infection; i.e. 4 to 6 weeks. By changing the processing variables, one is able to control the release rate of the beads. This provides advantages of meeting the specific antibiotic requirement for patients with various surgical infections.
Generalized Predictive Observer-Controller For Injection Moulding
Authors: Huang S. N. , Tan K. K. , Lee T. H.
Published: December 2013

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Evaluation of a Model Describing the Advancing Flow Front in Injection Moulding
Authors: Pisciotti F. , Boldizar A. , Rigdahl M. , Aronsson G.
Published: December 2013

The simulation of the advancing flow front during mould filling in the injection moulding cycle is important as a way of anticipating manufacturing defects, particularly different types of welds, air traps, cold spots and hot spots. The purpose of the present work was to evaluate a model (the distance model) simulating the advancing flow front and predicting potential issues related to the progression of the flow front such as welds and air traps. The distance model is based on a mathematical theory of Hele-Shaw flow for strongly shear-thinning fluids, i. e. fluids with a power-law index, n, equal to 0,3 or preferably less. Two grades of general-purpose polystyrene were selected according to their abilities to shear thin (weakly or moderately strong) at the selected processing temperature and in the typical shear rate range of the injection moulding process. The two grades were injection moulded into twelve mould configurations derived from two similar single-gated moulds. The flow length from the gate to the weld was measured in the mouldings obtained at three distinct rates of filling (conventional, slower and faster) and compared to the flow lengths obtained by the distance model. Good agreement was found between the predicted flow lengths and the experimental flow lengths at the conventional and faster filling conditions. Larger deviations between simulation and experiment were found at the slower filling rate, particularly for the weakly shear-thinning polystyrene grade. Some comparisons were also made with the predictions obtained using the commercial simulation code Moldflow. A comparison between the advancing front predictions of the distance model and experimental short shots of a commercial polypropylene grade in a lure-box type of mould geometry showed that the distance model, despite its simplicity, could probably be used to detect welds and air traps in more complex and practice-related mouldings.
Analysis of Heat Flu from Molten Polymers to Molds in Injection Molding Processes
Authors: Shiraishi Y. , Norikane H. , Narazaki N. , Kikutani T.
Published: December 2013

The inverse analysis method is applied in the evaluation of heat flux at the interface between the molten polymer and the mold during the injection molding process. In addition, the dependence of cooling behavior on both the molding conditions and the material properties of the resin are investigated. During low-velocity polymer flow in the thick regions of the mold cavity, the heat flux in the later stage of the process evaluated through experiment correlates well with the theoretical results of equations describing heat conduction at the interface of two semi-infinite objects. In contrast, in the thin region of the mold cavity, the analyzed heat flux is greater than the theoretical result for high-velocity polymer flow, and the difference expands with an increase in the shear rate at the wall of the mold. Based on these results, a simple empirical equation applicable to a wide range of molding conditions is proposed for the estimation of heat flux at the polymer-mold interface.
Process Design for Reducing the Warpage in Thin-walled Injection Molding
Authors: Wang T.-H. , Young W.-B. , Wang J.
Published: December 2013

The process design of the thin-walled injection molding is investigated in this study. It was realized that the behavior of warpage in injection molding parts was affected by different process conditions such as melt temperature, mold temperature, packing pressure and injection rate. Experimental design of Taguchi method was used to determine the process conditions. Both the numerical simulations and experiments were conducted to study the effects of the process conditions on the warpage of a cap model. The proper processing parameters were also identified by the experimental design. The packing pressure was found to be the most important factor on the warpage of a thin-walled part. The experimental design done by numerical simulations also provided proper results in terms of warpage reduction.
Optimization of Processing Conditions for Polymer Twin-Screw Extrusion
Authors: Gaspar-Cunha A. , Poulesquen A. , Vergnes B. , Covas J. A.
Published: December 2013

The problem of setting the best operating conditions of a co-rotating twin-screw extruder is solved using an optimization approach based on Genetic Algorithms. Two possibilities are considered: i) the maximization of an objective function; ii) the simultaneous optimization of the individual criteria and the use of Pareto plots. The flow conditions inside the machine are simulated using the Ludovic© software. Various practical case studies are discussed, among them a reactive extrusion application. Generally, the methodology is sensitive to the influence of the main process criteria and provides solutions that are apparently sound.
The Role of Tool/Sheet Contact in Plug-assisted Thermoforming
Authors: Collins P. , Harkin-Jones E. M. A. , Martin P. J.
Published: December 2013

Plug-assisted thermoforming produces a wide range of polymer products through a combination of deformation by air pressure and contact with tool surfaces. In this paper the role of tool/sheet contact in determining the process output is investigated. A combination of thermoforming, friction and heat transfer tests were carried out on common tool and sheet materials. The results show that the typical friction coefficients for the material combinations are within the range 0.1 to 0.3, but the values rise sharply on approaching thermoforming temperatures. Thermal imaging tests demonstrate that all of the plug materials significantly cool the heated sheet on contact, even over very short periods of time. The temperature of the plug is very important. At low plug temperatures heat transfer effects predominate, whereas at high plug temperatures friction effects predominate. A plug temperature of approximately 100°C balances these effects and creates the most effective material distribution.
Effect of Processing History on the Sintering of Ethylene Copolymers
Authors: Guillén-Castellanos S. A. , Lin W. , Bellehumeur C. T. , Weber M.
Published: December 2013

Polymer sintering plays a major role in processes such as rotational molding, governing the heating cycle and the properties of the final parts. There is evidence to suggest that the material molecular structure, molecular order and morphology are of importance in the sintering process. To date, however, there has been no satisfactory explanation as for their role in polymer sintering. One objective of this work is to examine the sintering behavior of ethylene copolymers under conditions related to the rotational molding process and to determine the relative effects of the polymer molecular structure and morphology on the sintering process. Sintering experiments were conducted under isothermal and non-isothermal conditions using both powder and cylindrical particles. It was found that the trends observed for the sintering of powder were consistent with the predictions of Newtonian sintering models. Sintering results obtained using cylindrical particles, however, showed significant differences not seen when using powder particles. These were attributed to the differences in the surface area between the two types of particles. It is speculated that the effect of material properties other than viscosity and elasticity are enhanced when cylindrical particles are used.
Five Geometric Principles for Injection Molding
Authors: Aronsson G.
Published: December 2013

A condensed presentation of some results of a geometric character, concerning the injection molding of plastics, is given here. The author has derived these results from mathematical arguments and some simplifying assumptions, besides the usual Hele-Shaw flow conditions.

The presentation here is intended for readers with an interest in polymer processing, rather than mathematics, so that the mathematical derivations are omitted in some cases, and sketchy in other cases. Instead we try to explain the results using figures, intuitive arguments and a few inevitable formulas. Since the experimental verification of the results is still very incomplete, we prefer to present them as proposed principles. Comments and suggestions for improvement are very welcome.
Modelling of Residual Stresses and Warpage in Sandwich Injection Moulding
Authors: Lundström T. S. , Toll S.
Published: December 2013

Sandwich injection moulding offers the possibility of combining materials with different properties and, for instance, hide a recycled constituent within a virgin ditto. This attractive potential puts great demands on the manufacturing and therefore also on the process modelling. In particular the effect on the final stress state and the deformation of the part due to the heterogeneity of the material must be clarified. This topic is addressed in this study. To start with it is confirmed that expressions for the temperature field can be much simplified without major loss of accuracy in the solution. This enables us to take an analytical approach to the modelling and the resulting equations can be solved on a spread-sheet or with a simple code. It is also shown that the derived models compare well to experiments made with a two-layered structure, indicating that the models presented can be used to estimate changes of processing conditions or material properties for sandwich structures.
Analysis and Optimization of Kenics Static Mixers
Authors: Galaktionov O. S. , Anderson P. D. , Peters G. W. M. , Meijer H. E. H.
Published: December 2013

The mapping approach is applied to study the distributive mixing in the, widely industrially used, Kenics static mixer. The flexibility of the mapping method makes it possible to study and compare thousands of different mixer layouts and perform optimization with respect to macroscopic homogenization efficiency and interface generation. In the paper two different designs of the mixer are investigated. The conventional mixer with sequentially different twisted blades and adesign where the twist direction is maintained constant. In both cases the blade twist angle is varied. Recommendations are given in the choice of the design of the mixer dependent on the desired structure of mixing.
Flexible Sheet Molding Compound (SMC) Using Aliphatic Polyester as Cross Linker
Authors: Esfandeh M. , Ebrahimi M. R.
Published: December 2013

Thermoset resins are brittle and have a poor resistance to crack initiation and growth. This is attributed to their amorphous and highly cross-linked structure. In composite parts made from thermoset molding compositions such as Sheet Molding Compound (SMC) and Bulk Molding Compound (BMC), the initial stage of composite failure is attributed to the properties of the polyester based resin. Thus, improving resin properties by adding various additives has been an interesting area of research. In this work, Maleic anhydride-terminated polycaprolactone (MATPCL) was used to modify the flexural properties of unsaturated polyester (UP) resin. MATPCL was prepared in the lab and was added to UP at 3, 5, 10, 20, 40 and 50 percent by weight. Mechanical properties of the cured samples (flexural and impact strength) were determined and an almost linear increase in impact properties was observed with increasing the MATPCL content. Phase behavior of UP/MATPCL blends was inspected both visually and using scanning electron microscopy and, no gross phase separation was seen at the levels used. SMC was prepared in conventional method using chopped glass fibers and the resin formulation having 20 wt% of MATPCL. Thickening behavior, molding characteristics, mechanical properties and fracture behavior of the prepared sheets were determined and compared with the sheets made from non-modified UP resin.
Neural Network Approach to Density Control of Rigid PVC Foam in Extrusion Process
Authors: Abu-Zahra N. H.
Published: December 2013

In rigid PVC foam extrusion, foam density is very crucial in determining the mechanical characteristics of the extruded material and the profitability of the manufacturing process. This paper presents a new application of artificial neural computing in the control of PVC foam density in profile extrusion process. A 3-layer multi-layer perceptron (MLP) artificial neural network was developed to estimate the foam density (weight) based on the known processing conditions; mainly heating zones temperatures and screw speed. The network was developed and tested on a specific formula that is used in wood-like products. A two factorial design of experiment was carried out to determine the significant process variables before training the neural networks using a back propagation algorithm. Finally, a comparison between the true weights, and the estimated weights using artificial neural networks is presented.
A Dynamic Model Accounting for Oscillating Behavior in Reactive Extrusion
Authors: Janssen L. P. B. M. , Rozendal P. F. , Hoogstraten H. W. , Cioffi M.
Published: December 2013

A qualitative mathematical model on the oscillating behavior of reactive extrusion is presented. Through the introduction of stagnant volume build up in the die as a result of the ongoing reactive extrusion process, a variable time dependent die resistance emerges. A differential equation for the waxing and waning of stagnant volume in the die is developed. This equation is able to give oscillating behavior for certain extruder parameters and viscosity when coupled to an existing dynamic model of the fully-filled length. The effects of reaction rate, rotational speed, feed rate, die resistance and degree-of-fill are studied.
On the Residual Stress and Shrinkage in Injection Compression Molding
Authors: Young W.-B.
Published: December 2013

Injection compression molding is a process having a compression action in the filling or postfilling stages. This process is suitable for molding of parts with precision features. The success of an injection compression molding process relies on proper design of the mold and selection of process conditions. The main scope of this study is to develop an analysis tool for the residual stresses and shrinkage of an injection compression molding process. A simple thermoviscoelastic model was used to calculate the stress and relaxation developed in the postfilling stage. The model divides the thickness into two regions, glassy and rubbery phases. Residual stress calculation is applied in the glassy region, while the rubbery region is kept at the melt pressure without any strain because of the fast relaxation in this region. The resulted in-mold stress fields are used to calculate the part shrinkage after demolding. The effects of the compression force on the residual stresses and shrinkage of a molding part were also investigated. Higher compression force tends to reduce the part shrinkage but induces a higher level of residual stresses.
Prediction of Residence Time Distribution in EZ and KE Element of a Ko-Kneader by using CFD Method
Authors: Mehranpour M. , Nazokdast H. , Dabir B.
Published: December 2013

Residence time distribution is among the important parameters of the Buss Ko-Kneader which allows one to better understand the flow conditions inside the system and to get information on mixing efficiency. However it has always been a difficult task to predict the RTD of complex geometries such as Buss elements.

The aim of the present work was to estimate the residence time distribution in EZ and KE element of the Buss Ko-Kneader by utilizing an elemental tracing method performed on the flow fields in the same elements which were analysized by CFD method. The effects of rotating and reciprocating motions of the screw have been taken into account in three dimensional flow analysis. It was demonstrated that these results can provide valuable information on mixing performance of these two elements.
Prediction of Residence Time Distribution for Different Screw Configurations of a Ko-Kneader by using a Cluster Model
Authors: Mehranpour M. , Nazokdast H. , Dabir B.
Published: December 2013

Prediction of residence time distribution (RTD) in the modular type screw extruders has always been one of the most attractive subjects for predicting. In the present work an attempt was made to establish a method with functionality similar to additive rule for predicting RTD of the modular screw extruders with different configurations such as Buss Ko-Kneader. Results predicted from this method, which was named as cluster model, were compared with the results predicted based on our previously reported trajectory method as well as experimental results. A reasonability good agreement was found between these results justified reliability of the cluster model for being used as a new approach to predict the RTD of the modular screw extruders.
Measuring Polymer Melt Density and Viscosity in Real-time during Extrusion Processes using Ultrasound Sensors Fusion
Authors: Abu-Zahra N. H.
Published: December 2013

A dual-sensor system is developed to measure the density and viscosity of polymer melts, simultaneously, during extrusion process. The sensory system utilizes a 2.25 MHz longitudinal ultrasound transducer in conjunction with a 2.25 MHz shear type ultrasound transducer, placed in a modified extrusion die. The acoustic impedance of the polymer melt, corresponding to the longitudinal ultrasound waves (UTL), is used to measure the density of the polymer melt using established physical models. While, the acoustic impedance of the shear waves (UTS) is used to measure the viscosity of the polymer melt, utilizing the density measurements obtained by the longitudinal ultrasound transducer.

The system was evaluated using polyvinyl chloride compounds containing various levels of foaming agent and processing aid at fixed processing conditions. The system measurements of the melt density was compared to the density of the extrudate, while the viscosity measurements were compared to the calculated values using slit-rheometry equations. The correlation coefficients between the ultrasound sensor and actual measurements were in the range of 92% and 96% for the melt density and viscosity; respectively.
Analysis of the Morphological Development of PBT/ABS Blends during the Twin Screw Extrusion and Injection Molding Processes
Authors: Ito E. N. , Pessan L. A. , Covas J. A. , Hage E.
Published: December 2013

The aim of this work was to observe the development of the phase morphology of the PBT/ABS blends during their extrusion mixing and injection molding steps. The evolution of the blend morphology during the mixing stage was analyzed using a specially designed co-rotational twin-screw extruder with a collecting device located along the barrel. Blend samples were collected in-line along the length of the extruder barrel during the blending process. Samples obtained from the extruded pellets and from injection molded specimens were also used to observe the blend morphology. All the samples were observed by transmission electron microscopy (TEM). They were prepared by cryo-ultramicrotomy and the rubbery phase of the ABS contained in the blends was stained with osmium tetroxide (OsO4). A special function was established and is proposed to analyze the blend morphology trends through image analysis. In binary blends, the ABS phase showed better dispersion after the mixture passed through the extruder die. However, a coalescence phenomenon was observed during the next molding step. Compatibilized PBT/ABS blends showed better dispersion than binary blends, even after injection molding. The special function used to quantify the dispersion throughout the mixing and molding steps showed an excellent performance.