bluuebunny/crossref_metadata_2025 huggingface dataset:
Squeeze Flow Rheology of Glass Mat Thermoplastic (GMT) in Large Tools and at High Closing Velocities
Authors: Vahlund C. F. , Gebart B. R.
Published: December 2013

Rheological measurements on materials with fibre-like inhomogeneities will be significantly affected by sample size when the in-plane dimensions of the sample are comparable with the length of the fibres. In this paper, a 310 t hydraulic press has been modified for squeeze flow rheology studies so that large tools that will minimize the influence of sample size can be used in combination with high closing velocities. Isothermal squeeze flow rheology experiments of GMT have been performed for closing velocities up to 30 mm/s corresponding to maximum closing forces of 1000 kN. Successful power law fits of closing velocity versus closing force have been performed for the velocity interval. Four different analytical models have been fitted to the experimental data and the accuracy in these has been investigated. The force prediction of the biaxial extension model is acceptable for the major part of mould closure, but better fits during the last part of mould closure were obtained using an additive model incorporating both shear and extensions flow.
A 3D Numerical Study of Fluid Flow and Heat Transfer in a Single Screw Extruder
Authors: Kwag D.-S. , Lyu M.-Y. , Kim W.-S.
Published: December 2013

A numerical study of three-dimensional fluid flow and heat transfer in the metering section of a single screw extruder has been performed. The screw channel was simplified by unwinding the channel and the coordinate system was fixed on the screw root in the present model. The pressure distribution over the inlet region was to be extrapolated from the solution of interior pressure. The prescribed mass flow rate was imposed on the outlet of the unwinding screw channel. The three-dimensional velocity fields, temperature, viscosity, and pressure profiles in the screw channel were calculated by using the commercial code, STAR-CD, based on the finite volume method.

Some of the results of the present full 3D model were compared with the results from the marching-type 3D model. It is shown that the present work can capture the back flow by the pressure gradient near the screw root in the cases of small mass flow rates. There exist significant discrepancies in temperature between the marching-type 3D model and the present 3D model. The present work well describes the effects of heating-up through the circulation flow and viscous dissipation. The cross-section contours of velocities, temperature, viscosities and pressures along the down-channel direction are also shown in this study.
Design Sensitivity Analysis Applied to Injection Molding for Optimization of Gate Location and Injection Pressure
Authors: Kabanemi K. K. , Hétu J. F. , Derdouri A.
Published: December 2013

In this work, we develop a numerical simulation method to optimize the injection molding process using the design sensitivity analysis (DSA). The optimization concerns the filling stage and focuses on the location of gates in the mold cavity as well as the injection pressure profile, in order to minimize the fill time. Since the problem to be solved involves transient flow with free surface (flow front), the direct differentiation method is used to evaluate the sensitivities of the Hele-Shaw, filling fraction and energy equations with respect to the design variables used in the analysis. The search domain parameterization is coped with using B-spline functions. Sensitivity and state equations are solved by means of finite element method. The proposed numerical approach is combined with the sequential linear and quadratic programming method of the design optimization tools (DOT) to find new design variables at the end of each complete filling simulation. Starting from any initial gate locations and injection pressure profile, the iterative optimization procedure enables us to find the optimal gate locations together with the optimal injection pressure profile. Finally, numerical results involving complex mold geometries are presented and discussed to assess the validity and robustness of the proposed method.
Polymer Melt Impregnation of Glass Roving
Authors: Bates P. J. , Zou X. P.
Published: December 2013

Much attention has been recently focussed on the melt impregnation of thermoplastic polymers as a consequence of the difficulty involved in driving viscous polymer melt into a tightly packed fiber bundle. This work studies an impregnation process consisting a series of staggered cylindrical pins in a melt pool. A numerical model for evaluating the pressure generation in the wedge region between the roving/pin, the impregnation velocity of the melt through the glass mesh, and the resulting impregnation depth along the wedge is developed using relationships for pressure build-up in foil bearings and Darcy's law. The model results are compared with experimental melt impregnation data. The model adequately predicts the effect of melt impregnation process conditions on impregnation quality.
Operational and Design Study of RIM Machines
Authors: Santos R. J. , Teixeira A. M. , Costa M. R. P. F. N. , Lopes J. C. B.
Published: December 2013

Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) data is presented and used to characterize the dynamic behaviour of the flow field in a RIM machine, and the main flow patterns and mixing mechanisms are examined and established. A two-dimensional CFD model is used for the simulation of mass transfer and chemical reaction in the mixing chamber of a RIM machine. Some design and operational parameters are considered and its influence on the mixing behaviour of a RIM machine is analysed.
Flow Properties and Morphology of PC/LCP Blends Affected by the Addition of Glass Fiber and Resulted Mutual Influences
Authors: Zheng X. , Zhang B. , Zhang J. , Xue Y. , He J.
Published: December 2013

In-situ hybrid composites containing matrix polycarbonate, glass fiber and LCP are prepared. The morphology of LCP and the rheological behavior of the composites are described. The relationship between flowability and morphology is discussed. It is interesting to find that in some hybrid systems, composites containing more glass fiber have better flowability than composites containing less glass fiber. Glass fiber aspect ratio is an important factor that determines the flowability. Materials with short glass fiber have lower viscosities than the materials with long glass fiber. LCP morphology is another important parameter that determines the flowability of the composites. If LCP forms fibrils, the composites have better flowability. If spheres dominate the morphology of LCP, the materials have larger viscosity. The addition of glass fiber brings about new factors that influence the morphology of LCP. The LCP morphology is not only affected by LCP content, but also by glass fiber content and glass fiber length. LCP fibrils are promoted in some in-situ hybrid composites. A model is proposed to describe how fibrillation of LCP is promoted due to the addition of glass fiber.
Diameter Profile Measurements for CO2 Laser Heated Drawing Process of PET Fiber
Authors: Okumura W. , Kanegae T. , Ohkoshi Y. , Gotoh Y. , Nagura M.
Published: December 2013

Poly (ethylene terephthalate) (PET) fiber was heated by carbon dioxide laser radiation in the continuous drawing process. By this procedure, the position of the deformation region could be fixed precisely in the air. The location of neck-like deformation fluctuated within a range of about 0.2 mm for draw ratios of 4.0 to 4.5 and within a range of about 0.5 mm for draw ratios of 5.5 to 6.0, but the location fluctuated over a range of 1.0 mm for a draw ratio of 5.0. Fiber diameter profiles, which were used to calculate Hencky strain rate profiles and apparent elongational viscosity profiles, were obtained from high-speed video camera images of the deformation region. Regardless of draw ratio, apparent elongational viscosity exhibited almost the same minimum value. Apparent elongational viscosity is much lower than the value obtained by measurement at a low, constant strain rate, but the elongational stress acting at the point where apparent elongational viscosity begins to increase steeply (Hencky strain of about 1.0) is of the same order of magnitude as the reported value. For draw ratios less than 5.0, the temperature where apparent viscosity is lowest is about 100 to 120°C, which corresponds to the flow temperature of amorphous PET, whereas for draw ratios exceeding 5.0 the temperature where apparent viscosity is lowest is about 80°C, which corresponds to the glass transition temperature. Thus, the former corresponds to so-called neck-like deformation typically observed in high-speed spinning, and the latter corresponds to necking typically observed in cold drawing. These two types of deformation appear in turns for a draw ratio of 5.0, and therefore the location of the deformation region fluctuates greatly. This measurement system can be used as a high-strain-rate elongational rheometer for analyzing practical polymer processing systems, which can easily measure the precise on-line deformation history with a time resolution in the μs level.
Cast Film Problem: A Non Isothermal Investigation
Authors: Sollogoub C. , Demay Y. , Agassant J. F.
Published: December 2013

An important problem arising in the cast film process is the so-called neck-in phenomenon, which may induce a drastic film width reduction as well as an inhomogeneous film thickness distribution (with the so called “dog-bone” defect on each side of the film). This neck-in phenomenon is highly influenced by the polymer rheology (increasing polymer elasticity leads to decrease markedly the neck-in), the stretching distance, the cooling conditions and the draw ratio. In this paper, we present a 2D Newtonian non-isothermal model based on a membrane approximation for the film. Stress balance, mass balance and temperature balance equations are solved iteratively using various finite element methods adapted to free surface problems and to transport equations. Coupling between mechanical and thermal equations is achieved introducing an Arrhenius temperature dependance for the viscosity. The influence of the heat transfer coefficient has been carefully investigated.
Single Screw Extrusion of Natural Fibre Reinforced Thermoplastics (NFRTP)
Authors: Torres F. G. , Ochoa B. , Machicao E.
Published: December 2013

Natural fibre reinforced thermoplastics are usually processed in twin screw extruders. The present work studies the single screw extrusion process for different systems of natural fibre reinforced thermoplastics. For this study different polymer-fibre systems have been characterised in terms of the material properties that are relevant to the processing behaviour of these materials. The extrusion process has been investigated using an open-barrel single screw extruder. This equipment can be stopped at any point in operation, cooled down and opened in order to study the material transport processes that take place inside the extruder. The polymer matrices used in this study have been mainly polyethylene and polypropylene (with MFIs varying from 0.3 to 4). Fibres including jute, sisal, and cabuya have been used as discrete reinforcements of a length of 5 to 10 mm.

The experiments presented here study the transport processes during single screw extrusion with special emphasis on the bubble formation mechanisms. The bubble formation process has been studied in terms of the variation in the initial fibre dispersion at the entrance of the feeding zone of the extruder. A relationship between solids conveying, plastication and bubble formation has been proposed considering the different typical cases occurring in the single screw extrusion of NFRTPs. The use of coupling and dispersion agents has been studied in terms of its relationship to bubble formation and to the final quality of the extrudates produced.

Finally, morphological characterisation techniques have been adapted to understand the structure-property relationships in these materials during the extrusion process.
Study on Functionalization of Isotactic PP with Maleic Anhydride in an Internal Mixer and a Twin-screw Extruder
Authors: Ghahari S. M. , Nazokdast H. , Assempour H.
Published: December 2013

The grafting reaction of maleic anhydride to molten iPP was investigated in both an internal mixer and a twin- screw extruder. The influence of peroxide content, added maleic anhydride and process variables such as residence time, screw speed and reaction temperature were considered. The rate and level of grafting were quantitatively measured by FTIR and titrometery technics. Maximum level of grafting at constant peroxide content was obtained when concentration of added maleic anhydride reached up to 6%, above which is declined. The rate of grafting increased with increasing the peroxide content. However the β-scission of polypropylene was found to be taken place as a parallel competitive reaction which was intensified with increasing peroxide content. It was demonstrated that it is possible to make an optimization on the grafting reaction on the basis of experimental results in conjunction with a free radical kinetic model developed for this reaction.
A Powerful Universal Plasticating System for Single-screw-extruders and Injection-moulding Machines
Authors: Grünschloβ E.
Published: December 2013

The plasticating principle, named HELIBAR for single-screw-extruders [1 to 5] is described and recent experimental results with a HELIBAR - extruder Ø 50×34 D are presented. They prove, that with only one barrier-screw the most different thermoplastic polymers can be processed successfully with very high throughput, good process stability, low melt-temperature and good melt-homogeneity. This concerns standard polymers (PE, PP, PS) and so-called technical polymers (PA, PC, PET, PBT, PMMA) as well as soft polymers and elastomers (PVC-W, PUR, TPE, EVA). Besides, this system in a standard design was tested successfully with a fast-running injection moulding machine Ø 70 × 23 D with different polymers (PS, PP, PE-HD). Compared to previous high-performance screws - with the same installed driving power - lower melt temperatures, good melt homogeneities and enhancements of the plasticating power between 20% and 100% were achieved.
Scale-up Rule for Double Bubble Tubular Process of PA6 Film
Authors: Takashige M. , Kanai T. , Yamada T.
Published: December 2013

The analysis of scale-up rule for double bubble tubular film process of PA6 was investigated. The scale-up rule previously proposed for a blown film process by the authors was applied to a double bubble tubular film process with a small-scale plant for research (pilot plant) and a large-scale plant for commercial production (production plant).

According to the scale-up rule based on the equivalent stretching stress between the pilot and production plants, the equivalence of stretching stability, birefringence pattern and deformation pattern were confirmed.

It has been confirmed that the proposed scale-up rule is applicable to predict the physical properties such as film impact strength and the bubble stability for the large-scale tubular film process on the basis of the experimental results obtained from the pilot plant.
Physico-Mathematical Model for the Description of the Temperature Development and the Power Consumption in Co-Rotating Twin Screw Extruders
Authors: Potente H. , Kretschmer K. , Pohl T.
Published: December 2013

Tightly intermeshing, co-rotating twin-screw extruders are commonly employed for tasks requiring good mixing. The modular constitution of both barrel and screw makes it possible to optimise the extruder configuration for a given task. Even today this optimisation is frequently done by applying the “Trial and Error”-method. Physico-mathematical models enable the process engineer to predict the process behaviour of a chosen extruder configuration and to optimise existing extrusion processes.

Increasing demands in mixing quality and efficiency of the processing unit result in efforts to optimise existing extruders with respect to those factors. For this reason knowledge concerning the temperature profile along the screw and the power consumption is essential. We present a new physico-mathematical model for the description of the temperature development. At stages where the analytical solution itself would result in a not satisfying degree of accuracy we used descriptions based on finite element simulation results to achieve the desired exactness. As a result we got a model to describe the temperature development in the screw channel and a model to describe the power consumption in different screw sections. Applying these models it is possible to optimise the process parameters and the screw configuration with only a minimum of preceding experimental investigations.
In-line Monitoring of PVC Melt Viscosity Using Dielectric Measurements
Authors: Abu-Zahra N. H.
Published: December 2013

A dielectric sensor, mounted in an extrusion die, was used to measure the dielectric properties of PVC melt during extrusion process. The dielectric permittivity and loss factor, of the polymer melt, were used to calculate the ionic viscosity and a dielectric viscosity index, which were correlated to the melt viscosity measured by slit rheometry equations. The viscosity of the PVC melt was varied by varying the level of chemical blowing agent (AZO) and processing aid (K400) in the polymer compound. The extrusion conditions; screw speed and heating zones, were fixed throughout the experiments. Strong correlation between the measured dielectric parameters and the melt viscosity was found to be consistent with established theoretical models. Therefore, this technique is capable of monitoring the viscosity of polymer melts accurately and reliably, in realtime, without disturbing the flow stream.
Extensional Rheology of Polypropylene in Relation to Processing Characteristics
Authors: Ivanov I. , Muke S. , Kao N. , Bhattacharya S. N.
Published: December 2013

Transient extensional rheological behaviour of several polypropylene (PP) homo- and co-polymer grades was studied at different temperatures. In addition, shear rheological characterisation was completed. The structure of PP grades was characterised by using gel-permeation chromatography (GPC), differential scanning calorimetry (DSC) and hot-stage optical microscopy (HS-OM). It was found that the extensional viscosity of the polymers followed the three-fold transient shear viscosity curves when the tests were conducted in fully molten state, as expected for linear polymer melts. However, the strain hardening behaviour was evident when PP was stretched in the semi-molten state, i. e. below its melting temperature (Tm). Similar to results of a recent study by Rauschenberger, three temperature zones of different extensional behaviour were found: linear viscoelastic behaviour and uniform drawing in the molten state (180 °C), unstable drawing just above Tm (170°C) and stable drawing with strong strain hardening below Tm (165°C). The strain hardening behaviour was quantified and related to molecular structure and morphology of PP. It was found that none of the investigated parameters alone was sufficient to predict the extensional behaviour of PP. The definition of Extensional Viscosity Index (EVI) as the ratio of extensional viscosities at the Hencky strain of 3 and 1, respectively, was found to be practical for the evaluation of the polymers' processability for the important industrial processes, such as BOPP film manufacturing, where extensional deformation predominates.
Deformation Behavior, Processability and Physical Properties for Biaxially Oriented Film of LLDPE
Authors: Uehara H. , Sakauchi K. , Kanai T. , Yamada T.
Published: December 2013

The bubble deformation behavior of double bubble tubular film (DBTF) of linear low density polyethylene (LLDPE) is experimentally analyzed. Also investigated is how the bubble deformation behavior of the stretched films are changed by stretching conditions, especially stretching temperature, and how the properties of stretched films are influenced by stretching conditions.

From the results, the optimum conditions required to obtain a stable bubble and good properties for the DBTF of LLDPE are indicated. The relationship between the DBTF and laboratory tenter stretched film (LTSF) is investigated in order to predict the processability and the properties of the DBTF by using the laboratory tenter biaxial stretcher. This method is not only more time efficient, but also reduces overall costs of developing the DBTF.
Engineering Analysis of Devolatilization of Various Additives in Intermeshing Co-rotating Twin Screw Extruders
Authors: Keum J. , White J. L.
Published: December 2013

An experimental study of devolatilization of nonane, xylene and 1-hexanol from molten polyethylene in a modular co-rotating twin screw extruder is described. Various modular screw designs, as well as different feed rates, screw speeds, and barrel temperatures were used. It was found possible to correlate the extent of devolatilization in different modular screw designs with a mass transfer coefficient which depends on screw speed and LDPE feed rate. The mass transfer coefficient depended on the liquid being devolatilized, being highest with 1-hexanol and lowest with nonane. In addition, the values of the mass transfer coefficient were obtained through experiments on the twin-screw extrusion of PE with nonane, xylene and hexanol. Interpretations of these results are described.
Reactive Extrusion of SAN/EPDM Blends
Authors: Hrnjak-Murgić Z. , Kratofil L. , Jelčić Z. , Jelenčić J. , Janović Z
Published: December 2013

The blending of styrene-acrylonitrile copolymer (SAN) and three different types of ethylene-propylene-diene terpolymer (EPDM) by reactive extrusion was studied and the free radical initiators: 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane (Luperco 101 XL), 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3 (Luperco 130 XL), α,α′-di(t-butylperoxy)diisopropyl-benzene (Peroximon F40) and 2,2-azo-di-(2-acetoxy)propane (Luazo AP) were used. Besides, structural characteristics of the obtained blends, some rheological and mechanical properties were also established. The rheological behavior was determined using rheometer and corotating extruder. Measurements of mechanical properties included: tensile strength, impact strength and elongation at break have been made. Blends were separated on its structural components SAN, EPDM, graft (EPDM-g-SAN) and gel content, which were further characterized by solution viscosimetry and IR spectrophotometry. The obtained results elucidate the reactions that occur during extrusion process. The dominant grafting reaction was observed in blends prepared by using a Peroximon F40 as an initiator also showing outstanding mechanical and processing characteristics.
Studies on Methacrylate-hydroethyl Methacrylate Oil-absorptive Fiber
Authors: Feng Y. , Xiao C. F.
Published: December 2013

A concept of potential crosslinker was introduced into the synthesizing process of highly oil-absorptive resin which is traditionally prepared by single chemical crosslinking. The resin was dissolved in DMAc and then span into fiber. The fiber was heated after spinning to obtain three-dimensional network structure. The effects of potential crosslinker content, crosslinked time and crosslinked temperature on the absorptive properties of fiber were studied. The structure of oil-absorptive fiber was analyzed by FTIR, DMA and SEM.
Flow Balancing in Extrusion Dies for Thermoplastic Profiles
Authors: Nóbrega J. M. , Carneiro O. S. , Pinho F. T. , Oliveira P. J.
Published: December 2013

A computer code, previously developed by the authors for the automatic die design, is used to optimise the flow distribution in a profile extrusion die using two alternative strategies: one based on length optimisation and the other on thickness optimisation. The numerical predictions are then compared with experimental data gathered during extrusion experiments. The numerical predictions and the experimental results agree within the experimental uncertainty thus showing the effectiveness of the computer code, the optimisation algorithm and the design strategies implemented. Generally speaking, measured and predicted values of pressure drop and flow rate are in good agreement (within 8 % and 6 %, respectively). It also is confirmed that optimisation based on thickness control leads to final profiles that are more prone to distortion.
Numerical and Physical Modeling of Polymer Crystallization
Authors: Haudin J.-M. , Chenot J.-L.
Published: December 2013

In this first paper, we have revisited Avrami's model and cast its basic equations into a differential system. This system is integrated numerically, which avoids unnecessary simplifying assumptions generally used in order to get analytical expressions. This allows us to introduce the variations of nucleation and growth parameters as a function of processing ones (temperature, cooling rate, shear rate, etc.). Our analysis shows that it is necessary to take into account the variation of the initial number of potential nuclei with temperature, which was usually ignored. Finally, an outpout of our calculations is the size distribution of the morphological entities, i. e., a quantitative information on microstructure.
Dry Spinning of Polymer Fibers in Ternary Systems
Authors: Gou Z. , McHugh A. J.
Published: December 2013

This paper addresses the development and application of a two-dimensional, three component model for the dry spinning process of polymer fibers. The model presented is an expansion of a previously developed two-component dry spinning model [1] that incorporated both viscous and viscoelastic effects in the constitutive equation for the spin fluid, along with two-dimensional effects to account for radial variations in the fiber temperature and composition profiles along the spin line. The model presented in this paper includes the effects of water in the spin dope through incorporation of the diffusion equations for ternary mass transfer. Mass and energy balances on the gas side are also taken into account so that the effects of ambient conditions can be investigated. Calculations are based on the system: cellulose acetate-acetone-water. Results are presented for profiles of solvent concentration, temperature, and glass transition temperature profiles for typical industrial operating conditions. Force and stress distributions in the fiber at various points along the spinline, analyzed in terms of contributions from the viscoelastic and viscous terms in the constitutive equation, illustrate the role of these stresses in the freezing in of structure along the spinline. Model predictions are shown to be in good agreement with the principal characteristics of dry spinning.
Side Chain Extension of Maleated Polypropylene with Diamine
Authors: Kim K. Y. , Kim S. C.
Published: December 2013

In this study melt reaction of maleated polypropylene (PP-g-MA) with hexamethylene diamine (HMDA) and poly(propylene glycol)-bis-(2-propylamine) (Jeffamine D-400) was carried out. Three kinds of PP-g-MA (Polybond 3002, Polybond 3150 and Polybond 3200) having different maleic anhydride content of 0.2, 0.5, 1.0 wt.% respectively were used. FTIR spectra show that branches and crosslinks were formed through the formation of amide and imide linkages between maleic anhydride group and diamine, and titration results show that the reactivity of HMDA to maleic anhydride group is higher than that of Jeffamine D-400. For Polybond 3002, increases in melt index and decreases in molecular weight was found after reaction as a result of chain degradation. Hence increases in viscosity and moduli were not found in reacted Polybond 3002. Polybond 3150 and Polybond 3200 with higher MA content shows increase in molecular weight after reaction, and gels were detected when high concentration of HMDA was reacted. Increases in shear viscosities and modulus were observed in Polybond 3150 and Polybond 3200. In elongational viscosity measurement, when higher concentration of HMDA used, strain hardening was observed in Polybond 3150 and Polybond 3200.
Mold for Manipulation Microstructure Development
Authors: Silva C. A. , Viana J. C. , Dias G. R. , Cunha A. M.
Published: December 2013

The control of microstructure development in injection molding had attracted several important studies in the recent years, being well established that the thermo-mechanical environment imposed to the polymer melt depends on the material properties, molding geometry and processing conditions.

An entirely new design of an injection mold RCEM (Rotation, Compression and Expansion Mold) was developed and implemented, allowing for a wide variation of the filling and packing conditions in a flat disk geometry. One of the cavity walls (the ejection side) can rotate or move with a linear movement during the injection and holding stages. This enables several filling sequences and the variation of the cavity thickness. Two electric servomotors are use to directly drive those movements. Two temperatures and pressure sensors allow for the on-line process monitoring.

Several examples of the potential uses of the RCEM are shown for the cases of amorphous and semicrystalline polymers. Results obtained with short-fiber reinforced polypropylene are also presented.
Structure Development in Injection Molding: A 3D Simulation with a Differential Formulation of the Kinetic Equations
Authors: Smirnova J. , Silva L. , Monasse B. , Chenot J.-L. , Haudin J.-M.
Published: December 2013

The purpose of the present work is to introduce a crystallization law into Rem3D, a 3D code written in C++ and dedicated to the injection molding of polymers. We kept the basic hypotheses of Avrami's model and cast the kinetic equations into a differential system that is solved numerically. The variation of the density of potential nuclei with temperature is taken into account. Furthermore, the distribution of mean spherulite sizes can be deduced from the calculations. The second part of the paper is an experimental study of crystallization in well-controlled conditions (2D, isothermal or constant cooling-rate). It establishes a procedure for the determination of the nucleation and growth parameters used in the theoretical model, and gives a first validation of this model. Finally, the crystallization equations are introduced into Rem3D, in order to assess the feasibility of our new approach. Some typical results concerning the evolution of the transformed volume fraction in injection-molded parts are presented.
3D Simulation of Gas Assisted Injection Molding Analysis of Primary and Secondary Gas Penetration and Comparison with Experimental Results
Authors: Polynkin A. , Pittman J. F. T. , Sienz J.
Published: December 2013

Techniques for the three dimensional simulation of gas assisted injection molding (GAIM) are presented, including analysis of primary and secondary gas penetration and the use of time and position dependent heat transfer boundary conditions, computed in a segregated 3D analysis of conduction in the tool, through many cycles of moulding. Predictions are compared with results of experimental trials using a mould tool with a glass window that allows video recording of the process. Accurate agreement is obtained for gas penetration distances in primary and secondary penetration and for the forms of the gas channel cross sections, in a part that incorporates typical features of a GAIM application. The success of the simulations relies on careful detailing of the computational model and numerical procedures, including the use of dynamically updated flow and heat transfer boundary conditions, the use of sufficiently high resolution meshes, and efficient, high accuracy iterative solution techniques.
Effect of Material Species on Flash Generation of PPS/GF Composites
Authors: Higuchi H. , Goto H. , Koyama K.
Published: December 2013

Reduction of flash in injection molding is of great concern for manufacturers of electrical parts. In a previous report we have proposed a theoretical model for flash generation. The present study prepares five different poly(phenylene sulfide)/glass fiber composites using three different PPS; linear, branched and crosslinked PPS and measures the length of flash generated in the molding of the composites. Then, we have compared the flash data with a flash parameter defined in the model. This comparison has elucidated that flash length can be related with the flash parameter irrespective of PPS structure, as long as GF content is the same and the clearance of a gas vent is almost identical.
External Calibration in PA12 Tube Extrusion
Authors: Carin A. , Haudin J.-M. , Vincent M. , Monasse B. , Bellet G. , Amouroux N.
Published: December 2013

Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r, z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the calibration tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from calibration conditions.
Experimental Studies and Modeling of Development of Dispersion and Fiber Damage in Continuous Compounding
Authors: Shon K. , Liu D. , White J. L.
Published: December 2013

An experimental study of mixing of various particulates into synthetic elastomers and polypropylene is presented. For the elastomers, a batch internal mixer and a commercial continuous mixer were used to disperse various small particles including silica, carbon black, and CaCO3. For the polypropylene, this same continuous mixer plus a Buss Kneader, co-rotating twin screw extruder and an intermeshing counter-rotating twin screw extruder with different modular screw configurations were used to follow the dispersion of CaCO3. The breakage of glass fibers in these machines was also followed. Generally the most severe breakage of agglomerates and glass fiber was by modular intermeshing counter-rotating screws with special Leistritz elements. A model was developed for breakdown of agglomerates and fibers. The agreement with experiment was promising.
Reactive Processing of Thermoplastic Polymers: A Review of the Fundamental Aspects
Authors: Cassagnau P. , Bounor-Legaré V. , Fenouillot F.
Published: December 2013

The review is devoted to the fundamental aspects of the reactive processing of thermoplastic polymers. First of all, some reactive processing examples, including polymer grafting (vinyl silane, maleic anhydride) and/or functionalization, bulk polymerization (urethane, lactams, acrylate, ∊-capolactone), polyester modification and new copolymers synthesis, are presented. From a fundamental point of view, the review covers the state of the art in the domains of rheology (specifically modelling of rheo-kinetics), diffusion and mixing in highly viscous reactive or non reactive media. Finally, 1, 2 and 3-D simulation of the reactive extrusion process in twin-screw extruder is reported at the end of the review.
The Modelling of Mold Filling in Resin Transfer Molding
Authors: Gauvin R. , Chibani M.
Published: December 2013

The resin transfer moulding process (RTM) allows the industrial production of large FRP parts. In this technique layers of reinforcements (mats, woven rovings) are inserted into the mold cavity and resin is injected to fill the closed mold applying external pressure. Due to the strong interdependence between mold design, filling behavior and part quality it is most important to control the cavity pressure as the major influencing process parameter. A simple model is proposed to represent the pressure distribution during mold filling. It is based on Darcy's law for flow of liquids through a porous media and can be applied to single type or combinations of different reinforcements.
Rheological Characterization of Sulfuric Acid Solutions of Poly(p-phenyleneterephthalamide)
Authors: Kim B. C. , Hwang S. S. , Kim K. U.
Published: December 2013

Several grades of poly(p-phenyleneterephthalamide) (PPD-T) with different molecular weights were prepared. The rheological properties of sulfuric acid solutions of PPD-T were measured. In the vicinity of the critical concentration tan δ and η′/G′ exhibited a minimum value, but G′/2G″ and η* showed a maximum value. High concentrations produce an anisotropic phase. Tendencies of yield behavior were observed for these solutions in the anisotropic phase. Above the saturated concentration the solution system showed gel-like properties, i.e., with increasing concentration abrupt reduction of G′/2G″ and abrupt increases of η*, η′/G′ and tan δ were observed. With increasing temperature the viscosity of isotropic and anisotropic phases was decreased but that of biphase was increased. The critical concentration was reduced with increasing molecular weight, but increased with increasing temperature. Use of reduced variables seemed to eliminate molecular weight dependency on the critical concentration curve. The shear viscosity appeared to be proportional to (Mw)6.7.
Fiber Spinning with Molecular Models
Authors: Chen Z. , Papanastosiou A. C.
Published: December 2013

The isothermal fiber spinning of ciscoelastic liquid is analyzed successfully by means of the Curtiss-Bird integral constitutive equation derived from molecular theory, Glaerkin/finite element method, and Newton iteration. The analysis accounts for shear and elongational prehistories, and specified draw ratio or drawing force. Solutions are obtained at high values of elasticity, draw ratio and drawing force. The predictions agree with the analytic solution for Newtonian liquid in the limit of zero relaxation time and with experimental data from the literature on spinning of polystyrene and polypropylene melts.
Thermal and Crystallization Behaviour of Polyphenylene Sulfide in Engineering Polymer Blends with HDPE
Authors: Nadkarni V. M. , Shingankuli V. L. , Jog J. P.
Published: December 2013

The thermal and crystallization behaviour of polyphenylene sulfide (PPS) in its blends with high density polyethylene (HDPE) is reported. Three grades of HDPE ranging in MFI from 0.4 to 52 were used in the investigation. The effect of composition and molecular weight of HDPE on the crystallization process and morphology of PPS in the blends has been investigated by the technique of Differential Scanning Calorimetry (DSC).

In the blends, PPS crystallizes in presence of molten HDPE. It is observed that the morphology of PPS in terms of crystallite size and crystallite size distribution in the blends is significantly affected by blending with HDPE. The temperature onset of melting was found to increase with increasing HDPE content and the melting peak width was found to decrease with increasing HDPE content. This indicates a larger crystallite size and a narrower crystallite size distribution of PPS in blends. The effect is more pronounced in HDPE-rich compositions. The extent of the variation in the temperature onset of melting and peak width were comparable for all the grades of HDPE. The degree of crystallinity of PPS in the blends is reduced significantly (55–70%) in HDPE-rich blends. Therefore, it is concluded that the crystallization of PPS is affected by the presence of HDPE melt.

The crystallization scans of PPS in the blends, obtained in the cooling mode, did not show any evidence of accelerated nucleation. On the other hand, a marginal reduction in the temperature onset of crystallization was observed. The temperature range of crystallization of PPS in the blends was found to be less for all compositions except for 90/10 (PPS/HDPE). In summary it is concluded that blending of HDPE with PPS influences the crystal growth of PPS significantly although the effect on its homogeneous nucleation is also considerable. As a result, the morphology of PPS crystallized in blends is different from that of the homopolymer. The changes in the morphology of PPS are not sensitive to the molecular weight of HDPE probably because of the high temperature of PPS crystallization relative to the melting point of HDPE.
The Processing Science of Thermoplastic Structural Composites
Authors: Cogswell F. N.
Published: December 2013

A sound scientific basis for understanding what happens during the processing of materials, and how that stage affects the service performance of the structure, is an essential prerequisite to the development of efficient low cost fabrication technology. This paper considers the phenomena - chemical, thermal, thermodynamic and rheological - which occur during processing and reviews the information which we have available today as a basis on which to build a more comprehensive study and data base.
Effect of High Molecular Mass Tail in the Mol Mass Distribution of Polypropylene on Injection Molding
Authors: Qian R. , Guo M. , Li S.
Published: December 2013

The effect of high molecular mass (MM) tail in the molecular mass distribution (MMD) of polypropylene (PP) on injection molding has been studied using injection molded tensile bars from a commercial PP resin and two samples of the above resin deprived of the high MM tail in different degrees by controlled degradation during extruder reaction with an added processing aid named Promax. The central portions of the tensile bars were studied by polarizing microscopy of microtomed sections parallel and perpendicular to the melt flow direction, and by density and birefringence profiles across the thickness of the bar. Mechanical properties and acoustic emission behavior in stretching of these injection molded tensile bars are also discussed. The experimental results show that by stripping off the high MM tail in the MMD the injection molded tensile bar has smaller degree of crystallization, less frozen orientation, improved uniformity across the thickness and the thickness of the skin part is greatly reduced. Better quality of the fabricated articles is to be expected by using Promax with PP for injection molding.
Process Analysis of a Laboratory Internal Mixer
Authors: Menges G. , Grajewski F.
Published: December 2013

In order to gain an idea of the flow processes in an internal mixer coloured mixtures were produced. Using these the randomness with which the distribution of the flow properties in the mixing chamber occurs could be shown. The thermal boundary conditions were found to have a strong effect on the flow processes in several regions of the chamber. Further experiments showed that the feeding behaviour of the mixture between the rotors and the time required for the incorporation both depend highly on the wall temperatures. In practice, fluctuating wall temperatures are caused by start-up effects, because mixing is a discontinuous process. A model was developed with which the variation of the internal wall temperatures can be calculated. This forms a basis for estimating the conditions to adjust heating systems in order to minimize temperature fluctuations.
Rheovulkameter
Authors: Moos K.-H.
Published: December 2013

In practical rubber processing the compounds will be subjected to high shear rates. Hence in order to optimize processing conditions and also to guarantee a constant quality of the compounds it's a must to test processibility of rubber compounds in the shear rate range of practical processing. Processibility of rubber compounds is predominantly determined by its viscosity that's balanced by two effects; viscosity of these materials decreases drastically with increasing shear rate (pseudoplasticity) but increases markedly with the onset and development of curing. The rheovulkameter has been developped especially to take care of these effects and allowing to measure easily and fast processibility of rubber compounds under conditions of practical processing. It can be used like a capillary rheometer but like an injection molding tester as well. Rheovulkameter tests given information about both: flowing (Rheo-) and curing (Vulkameter) of rubber compounds and other curing systems, too.
Modelling Flow in Pin-Barrel Screw Extruders
Authors: Brzoskowski R. , White J. L. , Szydlowski W. , Nakajima N. , Min K.
Published: December 2013

The flow in a pin-barrel extruder has been analyzed based on a Newtonian fluid model. A numerical simulation based on the FAN method of Tadmor and his coworkers and an analytical model were used. The calculations show that the introduction of slices into screw flights and pins make the apparatus a much poorer screw pump. It would appear that the machine is though an effective continuous (distributive) mixing device.
Polymer Melt Temperature in Single Screw Extrusion
Authors: Wilczynski K.
Published: December 2013

An attempt of estimation of the melt temperature fluctuation (in a single screw extrusion) by means of dimensionless numbers has been made. To this aim the screw metering zone has been considered by presentation of equations of motion and energy which describe the polymer flow within that zone in a dimensionless form (a model of a viscoelastic fluid has been assumed). It has been shown on the basis of the performed measurements that the best correlation with the temperature fluctuation may be obtained by means of Fourier number. Applicability of that number for the estimation of the temperature fluctuation has been discussed. A concept of criterion of estimation of the temperature fluctuation based on the Fourier number has been presented which would take into account an influence of polymer melting upon said fluctuation. Use of that criterion has led to a good agreement (correlation) with the experimental results.
DSC Studies on Fibre-Filled Polyethylene
Authors: Hatakeyama T. , Kitano T. , Klason C.
Published: December 2013

Four kinds of inorganic fibres: carbon, silica glass, brass and aluminium, were filled in two kinds of low density polyethylenes (PE, Melt Flow Rates (MFR) at 190°C, 2.16 kg; 4 and 8 g/10 min) by extrusion molding. The filling ratio of fibres was varied from 0 to about 20% in volume. The melting and crystallization of the above systems were measured by differential scanning calorimetry. The fibre-filled PE was crystallized at a temperature higher than that of the original PE. This phenomenon was observed through a wide range of cooling rate. The temperature of the main melting peak moved slightly to the low temperature side and a broad shoulder peak appeared, as the filling ratio of fibre increased. It was also recognized that the maximum temperature of the molten state affected the crystallization behavior of the system. This was observed for the fibre-filled PE having low melt flow rate. The variation of fibre species scarcely affected the melting and crystallization behavior. The results suggested that the filled fibre accelerated the nucleation process and retarded the crystal growth of PE.
Computer Simulation of Melt Viscoelasticity Functions for Binary Polyblends
Authors: Plochocki A. P. , Dey S. K. , Kiani A.
Published: December 2013

Composition dependence of the polyblends' properties is usually associated with a synergism (the positive deviation from additivity). Using the bicubic spline interpolation technique and the melt viscoelasticity data the effects of shear stress on the location and intensity of the synergism is demonstrated for a set of binary mixtures of commercial polyolefins. Principal patterns of the “transient” and the “set-in” synergisms are identified.