bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological Changes of a Polymer Blend into a Twin-Screw Extruder
Authors: De Loor A. , Cassagnau P. , Michel A. , Vergnes B.
Published: December 2013

The dispersion of an elastomeric phase (blend of two miscible copolymers: ethylene-vinyl acetate and ethylene-methyl acrylate) in a polypropylene matrix along a corotating twin-screw extruder was studied experimentally. A sliding barrel allowed a direct access to the screws and thus permitted a rapid cooling and sampling. The dispersion of the elastomeric phase was controlled by scanning electron microscopy and the size distribution was obtained by image analysis. The particle size distribution was measured at different locations along the screws in order to quantify the evolution of the morphology. Complementary studies were carried out on a pre-shearing rheometer (Rheoplast) in order to study the influence of the mechanical treatment upon particle size. The dispersion of the elastomeric phase was observed at the capillary exit by the above mentioned techniques. The results of these different experiments enhance the importance of the melting mechanism and put in evidence that the final morphology of the blend is controlled by the opposite mechanisms of break up and coalescence.
Selecting Continuous Compounding Equipment Based on Process Considerations
Authors: Canedo E. L. , Valsamis L. N.
Published: December 2013

The most widely used pieces of equipment in plastics compounding are continuous mixers and intermeshing corotating twin-screw extruders. Key design aspects and processing characteristics of these two machines are compared and examples of processing typical compounds in both types of equipment are presented and discussed.
Peroxide Induced and Thermal Degradation of Polypropylene
Authors: Ebner K. , White J. L.
Published: December 2013

An experimental study of the peroxide induced degradation of polypropylene is described. Experimental studies in a batch mixer, a single screw extruder and in a Leistritz modular counter-rotating twin screw extruder are presented. Three different screw configurations were used in the latter machine. When comparisons are made at the same temperature, peroxide level and residence time, the greatest extent of degradation is found in the twin screw extruder and the poorest in the single screw extruder. These differences seem associated with the rapid effective melting in the twin screw extruder and the slow melting and poor mixing in the single screw extruder. Of the three modular twin screw configurations, the configuration containing no intense shearing elements is most effective. Experiments based on removing the modular screw and following the reaction as a function of position suggests that Leistritz shearing elements cause rapid heating and reaction of the peroxide before it is mixed into the polypropylene matrix.
Reactive Blending of Polyamide 6 and Polycarbonate
Authors: Valenza A. , La Mantia F. P. , Gattiglia E. , Turturro A.
Published: December 2013

In this work structure and mechanical properties of blends of bisphenol-A polycarbonate with polyamide 6 with different molecular weights and different terminal groups are presented. The results show the important role played in the change of the morphology and in the improvements of the mechanical properties by the increasing content of NH2 terminal groups. These results are attributed to the reactions during melt mixing of such groups with polycarbonate.
The Effects of Recycling and Degradation on Parison Extrusion
Authors: DiRaddo R. W. , Pecora L. , Garcia-Rejon A.
Published: December 2013

Finished goods manufactured by the extrusion blow moulding process are strongly dependent on the parison formation stage, since it is the primary step in the process. The magnitude of the die swell and the degree of sag exhibited by the parison, after being extruded from an annular die, are dependent on the material's molecular structure and strongly affect the performance of the final product. Repassing or recycling of polymeric materials results in degradation reactions that modify the molecular structure, and therefore of parison swell and sag. Polyethylene simultaneously undergoes crosslinking and chain scission. Polypropylene undergoes predominately chain scission. The extent of these degradation reactions can be minimized with the use of appropriate stabilizers. This work involves the study of the effects of repassing on the parison formation stage of extrusion blow moulding. The repassing of the same material gives a representation of what occurs when recycling is undertaken. The effect of stabilizer addition is also studied. Particular emphasis is placed on parison swell and sag.
Stationary and Dynamic Analysis of Film Casting Process
Authors: Barq P. , Haudin J. M. , Agassant J. F. , Bourgin P.
Published: December 2013

A viscoelastic model for PET cast film extrusion is developed on the basis of some important assumptions: constant width, vertical film, isothermal regime, Maxwell's constitutive equation. The general model is non-stationary, but it can be first used to cope with steady-state extrusion, which makes it possible to introduce the concept of “unattainable region”, as in fiber spinning. Then the dynamic responses to random or sinusoidal fluctuations of the chill-roll velocity are analyzed. The predictions of the thickness response are in good agreement with experimental observations.
Bulk Density of Plastic Pellets in a Screw Channel
Authors: Potente H. , Schöppner V.
Published: December 2013

For a correct calculation of the material throughput of single screw extruders in the by solids dominated feed area, the accurate knowledge of the effective bulk density is important. In the screw channel the bulk density measured in a quasi infinite vessel cannot be achieved during processing. The effective density is reduced according to the wall influences. If a two component system exists in the feed area, for example, when processing moulding compounds or regrind, then the bulk density changes likewise. In the following a procedure is described, by which the effect of the screw core measurement and the percentage composition of two material mixtures on the effective bulk density can be calculated.
Blending of SAN and SBS in Corotating Twin-screw Extruders
Authors: Kim Jin Kuk , Lee Si C. , Park Hyun K.
Published: December 2013

Polymer blends have been drawing attention with the development of the polymer industry. The characteristics of toughened SAN/SBS polymer blends are reported in this study. The effect of the screw configuration on the properties of polymer blends has been investigated. This study also deals with the effect of the operating temperature on the properties of the polymer blend. The microphotographs show SBS (Styrene-Butadiene-Styrene) domains in the SAN (Styrene-Acrylonitrile) matrix. This explains that the well dispersed rubber particles do not always contribute to the good mechanical properties such as impact strength. However, this effect contributed to the fluidity of the molten polymer blends.
Compounding and Morphology of Nylon/Ethylene-Propylene Rubber Reactive and Nonreactive Blends
Authors: Scott C. E. , Macosko C. W.
Published: December 2013

The processing behavior and morphology are investigated for nonreactive and reactive nylon/ethylene-propylene rubber blends. The nylon (PA) is a partially aromatic amorphous nylon with amine termination. The rubbery phases are an ethylene-propylene rubber (EP) and a similar ethylene-propylene rubber (EP-MA) with 0.7% grafted maleic anhydride. The nonreactive PA/EP blends show poor interfacial adhesion between the two phases. The reactive PA/EP-MA blends show excellent adhesion and much smaller dispersed phase domain sizes. The interfacial chemical reaction affects several separate parameters which influence the size of the dispersed phase: the formation of a copolymer at the interface which reduces the interfacial tension; different rheological properties of the modified and unmodified rubbers; the effect of the interfacial reaction on the rheology of the blend; changes in process parameters due to the effect of the interfacial reaction; reduction in the rate of particle-particle coalescence due to the presence of the copolymer at the interface; as well as other effects. A semi-empirical relationship is used to separate the effects of phase rheology and applied mixing stress.
Approximate Simulation Method on the Three-dimensional Polymer Melts Flow in a Die
Authors: Matsunaga Keishi , Sakaki Kazutaka , Kajiwara Toshihisa , Funatsu Kazumori
Published: December 2013

Two kinds of practical approximate simulation methods for three-dimensional viscoelastic flow in a die have been developed by which solutions at high shear rate can be obtained with low memory capacity and CPU time. The velocity and stress fields were calculated separately. The velocity field was obtained using the pure-viscous non-Newtonian model and the stress field using the viscoelastic model by substituting this velocity field. In one case the White-Metzner model was applied as a viscoelastic model without a square term in stress. In the second case the stress field was calculated by the streamwise integration which could apply even to the viscoelastic model including the square of stress. In addition a modified pure-viscous non-Newtonian model has been developed respresenting the strain-thickening elongational viscosity in order to extend these approximate methods to similar materials. The velocity field which was calculated using a modified pure-viscous non-Newtonian model was considerably closer to that for the viscoelastic model with the same flow characteristics as shown for the original pure-viscous non-Newtonian model.
On the Simulation of Thermoplastic Injection Moulding Process
Authors: Titomanlio G. , Speranza V. , Brucato V.
Published: December 2013

Numerical simulation of the injection moulding process of thermoplastic polymers has been performed on the basis of the Williams and Lord model and its recent extensions. The aim of the simulation was to identify material properties which play a relevant role to process modelling, including post filling stages. Predictions improve significantly by taking into account the effect of pressure on both viscosity and crystallisation kinetics. Several features, however, are not satisfactorily predicted. Also the relevance of convection during packing has been evidenced especially with reference to gate sealing time. As highly oriented crystalline structures are present in the final moulded object, the enhancement of crystallisation kinetics by the effect of flow is suggested as the phenomenon to be accounted for in order to gain a quantitative description of the whole process.
Control Volume Finite Element Method for Mold Filling Simulation
Authors: Wang T. J. , Lee L. J. , Young W. B.
Published: December 2013

This work presents two methods to improve the spatial accuracy of traditional control volume based finite element method for the mold filling simulation. The first method is based on the flow front mesh refinement which results in a better numerical accuracy near the flow front region without any need of remesh. The second method, flow front tracking, traces the exact location of the flow front. Together with local remesh, the spatial accuracy is improved. Application of both methods to the mold filling process in resin transfer molding (RTM) is presented.
Non-isothermal Dispersive Flow of a Rubber Mixture Inside an Internal Rotor Mixer
Authors: Malkin A. Ya. , Baranov A. V. , Dakhin O. Kh.
Published: December 2013

The paper is devoted to theoretical and experimental investigation of hydrodynamics, heat exchange and kinetics of dispersing of carbon black with a rubber mixture in a chamber of an internal mixer. Modeling of the process is based on use of a rheological equation of a “power” type. A possibility of slipping along a wall is taken into consideration in formulation of boundary conditions. Results of model calculations gave ground for the engineering method of calculations of optimal values of the size of the gap between a wedge of a rotor blade and a wall of a chamber. Comparison of such principal characteristics of a mixing process as average temperature of a stock and the degree of dispersion demonstrated quite good correlation of calculated and experimental data.
Mixing Ring
Authors: Ingen-Housz A. J. , Norden S. A.
Published: December 2013

A new mixing device, to be mounted on the tip of a single screw extruder, is equipped with a freely rotating ring. Its homogenising action is clearly understood and explained. In order to understand its dispersing action experiments have been performed in order to find proof of the presence of elongational flow. They regard visualisation of the flow in a transparent model and blending of PS into PE with various viscosity ratios. Aspects of design and applications are discussed.
Relationship of Stresses in Blown-film Processes
Authors: Kurtz S. J.
Published: December 2013

Fabrication conditions and material rheology control the process of film blowing and limit the possible shapes the bubble may take as well as the ranges and ratios of stresses within the bubble. In order to understand bounds on the stresses during the blowing process, we explore the constraints imposed by force balances, the thin shell approximation, and thermodynamics. We show that the ratio of axial stress to hoop stress is independent of the explicit terms for film thickness, velocity, heat transfer, and the rheology of the material. In addition, we demonstrate that the ratio of the axial stress to the hoop stress can be calculated at any point in the blown-film requiring only values for the pressure drop across the bubble, the shape of the bubble, and the force pulling up the bubble. Experimental results, as well as certain theoretical evidence, strongly indicate that the ratio of axial to hoop stress is everywhere greater than 1 in the standard blown-film process. If this is generally true, then the stress relations we derived can be employed to test the applicability of various theoretical models of the blown-film process.
Numerical Simulation of Polymer Forging
Authors: Haudin J. M. , Monasse B. , Valla T. , Glommeau S.
Published: December 2013

Previous work has shown that numerical simulation does not provide a correct description of compression experiments if the rheology of the polymer in the solid state is deduced from tensile tests. Therefore, a new method is proposed for the determination of the coefficients of G'sell's constitutive equation, in order to simulate the forging process. It also gives access to a parameter characterizing the friction conditions between the polymer and the tool. It is based on isothermal compression of polymer cylinders with an appropriate geometry and on its complete interpretation by means of computer simulation using the finite element code FORGE2. This original procedure is applied to polyoxymethylene.
Thermal/Peroxide Induced Degradation and Maleation of Polypropylene by Reactive Extrusion
Authors: Kim B. J. , White J. L.
Published: December 2013

Experimental studies of three types of reactive extrusion are reported: thermal degradation, peroxide induced degradation and maleation of polypropylene for intermeshing modular co-rotating and counter-rotating twin screw extruder. The studies were carried out in a modular intermeshing twin screw extruder which can be co-rotating or counter-rotating and possesses different screw configurations. Generally thermal degradation was found to be more effective in intermeshing counter-rotating twin screw extruders when similar screw configurations and operating conditions are used. For peroxide induced degradation both counter-rotating and co-rotating machines performed about the same. For the maleation reaction the co-rotating twin screw extruder achieves higher conversions than the counter-rotating machine with all screw configurations and conditions studied. It would appear that the intermeshing counter-rotating twin screw extruder operates at a higher temperature and has poorer mixing characteristics than the co-rotating machine. Differences between the co-rotating and counter-rotating machines decrease with introduction of kneading disc blocks.
Tubular Film Blowing
Authors: Liu C.-C. , Bogue D. C. , Spruiell J. E.
Published: December 2013

The literature on tubular film blowing is contradictory, even on such basic matters as to whether increasing inflation pressure increases or decreases the bubble radius. To provide a solid experimental base for physical understanding and theoretical modelling, detailed on-line measurements were made using three polyethylenes (a low density, a linear low density and a high density material, all of melt index 1.0). The measurements included blow-up ratio as a function of inflation pressure and take-up ratio; the melt temperature and the air flow rate were also varied. On-line radius, velocity and temperature measurements along the film were made in some runs. For the most part the data showed an “intuitive” effect of inflation pressure on blow-up ratio; that is, increasing the pressure caused the final radius (the blow-up ratio) to increase. However, at high blow-up ratios (typically values of 2 to 3, depending on the material and processing conditions), regimes having a “counterintuitive” relationship were observed in some cases. There were not substantial differences among the three materials except that the low density material was less prone to instabilities at high blow-up ratios.
On the Limitations of Shear Induced Crystallization in Polypropylene Melts
Authors: Liedauer S. , Eder G. , Janeschitz-Kriegl H.
Published: December 2013

Recently, the mechanism of shear induced crystallization in melts of isotactic industrial polypropylene has been unravelled for sufficiently high rates of shear [1]. This was achieved with the aid of, what we called, short term shearing. This shearing was applied in a rectangular duct of large aspect ratio. The development of crystallization subsequent to this short term shearing was monitored with the aid of the growing optical retardation. Other traits of this process could be deduced from the cross-sections of the samples extracted from the duct after complete solidification. Mainly one of these traits is the subject of the present paper. As with injection molding, highly oriented areas are found in the cross-sections. The laws governing the limitations of these areas are discussed. In other words, the dependence of the thickness of the layers on the previous shear rate and shearing time is described with the aid of a model containing the relaxation times of threadlike (liquid) precursors. These relaxation times are assumed to depend on the size of the precursors: The larger these precursors have grown the more stable they are assumed. Nucleation and growth are considered as statistical processes.
Dynamics and Structure Development in Spin Welding of Polyvinylidene Fluoride Cylindrical Rods
Authors: Schaible S. , Cakmak M.
Published: December 2013

Dynamics and structure development during the course of spin welding of polyvinylidene fluoride were studied using an instrumented spin welding machine. At least four distinct events were found to occur during the melting sequence that occurs during melting of interface. Wear of asperites, melting as a result of Coulombic friction, appearance of finger-like formations whose long axes aligned in the radial direction and final smearing of these finger-like formations transforming the topography of the interface to fibrillar appearance. In the formation of structural variations in radial and axial directions in the HAZ, the Weissenberg effect was found to play a substantial role.
A Throughput Model for Grooved Bush Extruders
Authors: Potente H. , Schöppner V.
Published: December 2013

On modern extrusion plants, polyolefins are generally processed using barrels that have a grooved feed section. Accurate calculation of the melt throughput is of decisive importance for the process engineering layout of these extruders. Up to the point at which the limit speed that gives rise to the conversion from solid friction to melt film friction is attained, the conveying capacity is determined by the feed zone that is filled with granules. This paper sets out a method of calculating the throughput for speeds below this limit, paying consideration to the melt flow components in both the screw channel and the grooves. The calculation method was verified experimentally with the aid of throughput measurements for different polyolefins. The results generally fall within a tolerance range of +/−10 %.
A Physico-Mathematical Model for Solids Conveying in Co-Rotating Twin Screw Extruders
Authors: Potente H. , Melisch U. , Palluch K. P.
Published: December 2013

Contrary to the case for the melt conveying zone, no adequate description exists as yet for the solids conveying zone of a co-rotating twin-screw extruder. A physico-mathematical model of the solids conveying zone, however, is a prerequisite for determining the location of the plasticizing zone and for establishing the optimum screw configuration that goes with a selected point of operation. This paper presents a physico-mathematical model to describe the processes taking place in the solids conveying zone. The conveying zone is divided into a partially-filled feed zone and a completely filled compression zone. Force and torque balances are drawn up for three different volume elements and, with the solutions obtained for these, it is possible to calculate the maximum conveyable throughput, the pressure profile over the length of the solid material accumulations and the drive power that is required or the solids conveying zone.
High-speed Melt Spinning of PET
Authors: Kikutani T. , Radhakrishnan J. , Sato M. , Okui N. , Takaku A.
Published: December 2013

The high-speed spinning process of poly(ethylene terephthalate) (PET) was modified by introducing a liquid isothermal bath (LIB) which was kept at a temperature of 155°C and placed at a distance of 150 cm or 200 cm below the spinneret. The structure and mechanical properties of the as-spun fibers thus produced in the take-up speed range of 1 to 7 km/min were characterized. The results showed that the introduction of the LIB significantly influences the structural development of the as-spun fibers. The fibers produced using the LIB in the spinline showed significantly higher birefringence and crystallinity compared to the fibers produced using a standard high-speed spinning process. A semi-quantitative numerical simulation was performed with the incorporation of the LIB in the spinline to understand the mechanism of fiber structure formation during the modified high-speed spinning process of PET. The results showed that the solidification stress is considerably high when the solidification was assumed to occur at a position close to the exit of the LIB. The enhancement of molecular orientation was attributed to the increased frictional stress induced by the liquid layer whereas the spinline crystallization was found to be influenced strongly by the temperature of the liquid.
Analysis of the Local Volume Flow Rate of Polymers During Injection Molding
Authors: Lacrampe M. F. , Pabiot J.
Published: December 2013

Amorphous and crystalline polymers were injected into different molds of disks, with different applied injection rates. The pressures and local volume flow rates were measured for different injection molding conditions. These measures show a difference between the average volume flow rate measured during the total filling time and the nominal applied volume flow rate. Moreover the local volume flow rate at the polymer front increases between the mold entrance and the end of the cavity. Effects of different parameters of the process (polymer, geometry of the part, injection molding conditions) on the evolution of these volume flow rates were examined. Interpretation of the observed phenomena neads to take into account the effect of two characteristics of the polymers which are generally neglected: the compressibility and the associated bulk viscosity.
Spinnability of Polymer Melts – a Complex Problem in Basic Research1)
Authors: Beyreuther R. , Vogel R.
Published: December 2013

Melt spinning of polymer melts is a formation process making extremely high demands on the material's continuous deformation ability by highest deformation speeds. The structural conditions of a thermoplastic polymer which are necessary for spinnability have not been exactly cleared up yet. But this knowledge gap must be closed especially with regard to the many efforts to spin fibers with new properties made from modified polymers or polymer blends. The article is begun with a pragmatic definition of the spinnability of a polymer melt. The discussion of a structural rheological model shows a correlation between dynamic rheological measurement datas of polymer melts and experimental experience about their spinnability. Proceeding from a comprehensive description of possible failure cases (fiber beak problems), results of rheological measurement of a number of different polymers, which are spinnable well, not as well or not at all, are compared. The article is concluded by some comments on open problems which have to be solved by basic research in the near future.
Inverse Modeling of Injection Molding Thermal Stresses to Optimize Temperature and Pressure History
Authors: Farhoudi Y. , Kamal M. R.
Published: December 2013

The dimensional stability and mechanical and optical properties of injection molded articles are affected to a large extent by the distribution of residual stresses. The distribution of residual stresses varies as a result of the temperature and pressure history during the process. In this paper, two thermoelastic models were used to study the effect of processing conditions on generation of thermal stresses. Then, based on these models, two inverse models were developed to calculate the unknown pressure history and initial melt temperature from a known residual stress distribution in the final product. The models were successfully tested with stress data simulated by the forward models. The effect of experimental errors on the inverse methods was investigated by adding random errors to the stress data. Finally, experimentally measured stress profiles were used to further test the inverse models. The results are presented and discussed.
An Assessment of Thermal Stresses in Injection Moulded ABS Copolymer
Authors: Akay M. , Ozden S.
Published: December 2013

Thermal residual stresses in injection mouldings result from the non-uniform cooling of the melt in the mould. Normally, compressive stresses develop at the surface and tensile ones within the core of the mouldings. The magnitude of these residual stresses was examined for an acrylonitrile-butadienestyrene copolymer (ABS) under various injection moulding conditions. Although the occurrences of thermal stresses are inevitable, the warpage results only when the residual stresses are out of balance. The imbalance of the residual stresses are caused by the non-uniform temperature distribution through the thickness of the mouldings which may be caused by variation in cross section, part geometry and temperature difference between the two surfaces. The magnitudes of thermal residual stresses in injection moulded ABS flat plaques were determined using a layer removal technique. The development of warpage in a 3D component (an L-shaped bracket) was modelled using the residual stresses obtained for the flat plaques and the predictions were compared with the experimental warpage measurements.
Experimental Study on the Injection Compression Molding of Parts with Precision Contours
Authors: Yang S. Y. , Lien L.
Published: December 2013

The thermomechanical history of the melt under injection compression molding follows a quadrilateral-shaped path, rather than conventional triangular-shaped path, over the P-v-T diagram. The control capacity and flexibility over post-filling is significantly enhanced. It thus can produce parts with better dimensional control with less frozen-in orientation than those from conventional injection molding. This paper is devoted to study its technological application on the precision molding of parts with precision contours. A modified injection molding machine incorporating compression mechanism, and a mold with movable wall and shut-off mechanism, are used. The quality of injection-compression-molded polysytrene convex lenses is defined and compared with those injection molded. With the same cooling time, injection compression can produce lenses with better quality than those without compression
The Effect of Injection Molding Conditions on the Mechanical Properties of an In Situ Composite
Authors: O'Donnell H. J. , Baird D. G.
Published: December 2013

The effect of processing conditions on the mechanical properties of an injection molded polypropylene/liquid crystalline polymer (PP/LCP) blend was studied. The LCP consisted of a copolymer based on poly(ethylene terephthalate) and poly-(hydroxybenzoic acid). Two PP matrices were used to vary the viscosity ratio of the blend. It was found that the highest flexural moduli were obtained for blends with the PP matrix that provided the highest viscosity ratios (closest to unity). These optimal properties were obtained only at one processing temperature, 250°C. At this temperature, the storage (G′) and loss moduli (G″) of the neat LCP were approximately equivalent. The optimal properties at temperatures where G′ ∼ G″ is in agreement with a prior study of another PP/co-polyester LCP blend [15]. Futhermore, the optimal properties were sensitive to the filling time. This was related to heat transfer via the Graetz number. For thinner molds, higher properties are obtained over a broad range of Graetz numbers (temperatures) while for thicker molds higher properties are obtained only at lower Graetz numbers (temperatures). The dependence of the flexural modulus on the Graetz number was related to the ability to deform the LCP at the advancing front and the ability to freeze the morphology possibly even before cessation of flow.
Defects in Resin Transfer Molded Plaques Due to Resin Age Distribution During Mold Filling
Authors: Losure N. S. , Jayaraman K. , Petty C. A.
Published: December 2013

This paper examines the development and consequence of flow structures and possible defects arising in multiple shot injection or multiple-gated injection of two-component resins mixed in-line into a mold with and without fiber preforms. This work may also be relevant to the packing stage. Experiments were run where a premixed batch of vinyl ester resin with peroxide and tracer dye, displaces another older batch of premixed resin in a mold. Polymerization of resin as it flows through the preform during the filling stage sets up an increasing viscosity profile along the fluid filled region and viscous fingering is observed as expected. The types of flow patterns associated with this phenomenon have been explored with random and woven fibrous media packed in a clear mold. The molded plaques were cut up and tested in 3-point bend so that the flexural moduli of specimens with various flow structures could be compared. The flow structures observed include fingers with rounded ends and fingers with multiple tips. Such flow structures lead to regions in the plaques where ‘packets’ of fluid with different extents of polymerization due to differences in age are juxtaposed prior to gelation of the resin. It was found that finger structures with several sharply defined interfaces tended to decrease the value of the flex modulus by up to 32 %, depending on the preform characteristics. Multiple finger tips with diffuse boundaries do not seem to be detrimental to the flex modulus, but multiple tips with sharp boundaries have lowered the flex modulus by 32%.
Biodegradable Poly(Lactic Acid) with High Molecular Weight
Authors: Miyoshi R. , Hashimoto N. , Koyanagi K. , Sumihiro Y. , Sakai T.
Published: December 2013

Biodegradable plastics have been quickly accepted as one of the key solutions for today's waste plastics problems in Japan. Particularly, poly(lactic acid) is looked forward to as the most promising biodegradable plastics because of its high quality in optical and physical properties as well as chemical recyclability and compostability. Furthermore, lactic acid as a raw material of this polymer can be produced from agricultural starch wastes. However, one of the greatest issues in biodegradable plastics including poly(lactic acid) and lactic acid-based copolymers lays in their extremely high price when compared to typical commodity plastics on the market. Regarding poly(lactic acid), a polymer with high molecular weight of more than Mw = 100 000 is conventionally obtained only by a ring-opening polymerization process from lactide, i.e., dimer of lactic acid, which is very expensive.

To aim at developing practical and economical technologies for effectively producing poly(L-lactic acid) as a representative of lactic acid-based polymer, we have been carrying out continuous melt-polymerization experiments using the combination of a batch type stirred reactor and an intermeshed twin screw extruder in this study. As a result, we have successfully obtained poly(L-lactic acid) with higher molecular weight of up to Mw = 150 000 from lactic acid by a continuous melt-polycondensation process.
Acceleration of Chemical Reaction in Reactive Extrusion Accompained by Devolatilization
Authors: Chen L. , Hu G. H. , Lindt J. T.
Published: December 2013

This work concerns the reaction acceleration in bubble enhanced devolatilization (DV) occurring in reactive extrusion (REX), to provide further evidence that overall reactivity can be enhanced by boiling. Using monoesterification of a styrenemaleic anhydride copolymer with an alcohol as a model reaction, the rate increase was determined by comparing the conversions of the samples collected at different screw locations with those predicted from the combined kinetic equation for the bubble free homogeneous system and the RTD information obtained from both the RTD measurements and theoretical calculations.

Significant reaction acceleration was observed. The reaction enhancement was found to be more significant than found previously by batch operation. Also, the reaction enhancement beyond the DV zone showed a trend consistent with the previous observations in batch after DV has been halted. Further, we show that the apparent reaction rate increase during continuous REX/DV is caused by local mass transfer effects, in agreement with the previous work in batch. The good agreement between the theoretical predictions and the experimental results, observed here, lends some extended generality to the mass transfer model for reaction acceleration during REX/DV.
Physically-Based Model of Thermoplastics Injection Molding for Control Applications
Authors: Rafizadeh M. , Patterson W. I. , Kamal M. R.
Published: December 2013

A non-linear mathematical model of the thermoplastics injection molding cycle is presented. The model is formulated based on the conservation equations for the filling, packing, and cooling phases. The whole process is divided into subsystems including the hydraulic system, ram-screw, barrel, and polymer delivery system. It is found necessary to account for polymer melt elasticity as well as the non-Newtonian behavior of the polymer melt flow. The growing solid skin in the sprue, runner, and gate are considered. The governing equations are solved numerically. Model predictions are in good agreement with experimental data for the injection molding of high density polyethylene. The resulting model is a useful tool for the study and design of injection molding controllers, machine parameter selection, and equipment design.
The Effect of Drawing and Annealing Conditions on the Structure and Properties of Bacterial Poly(3-hydroxybutyrate-co-3 hydroxyvalerate) Fibers
Authors: Yamamoto T. , Kimizu M. , Kikutani T. , Furuhashi Y. , Cakmak M.
Published: December 2013

The effect of drawing and annealing on structure development and resulting properties of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) fibers have been investigated. Melt spun and subsequently drawn and annealed fibers were characterized by wide-angle and small-angle X-ray scattering techniques. WAXS studies revealed that these fibers possess bimodal chain orientation with two populations of crystals: in the first population the chain axes are oriented primarily along the fiber axis and in the second population these chain axes are oriented in the transverse direction to the fiber axis. In the latter crystals, a- and b-axes are randomly distributed around their c-axes. At the annealing temperature of 100° C, the relative population of the crystals oriented normal to the fiber axis was found to be large and their proportion decreases with the increase of annealing temperature. SAXS patterns were found to accompany the changes observed in the WAXS patterns. The tensile strength of these fibers improved by the increase of the proportion of the transversely oriented chains.
Studies of the Trans-Quinacridone Nucleation of Poly-(ethylene-b-propylene)
Authors: Sterzynski T. , Lambla M. , Georgi F. , Thomas M.
Published: December 2013

The poly-(ethylene-b-propylene) was nucleated for a study of the structure modifications as well as the improvement of the mechanical properties, particularly the impact resistance. The nucleation was accomplished by two various red pigments: a linear trans-quinacridone dye (as ß-phase nucleator) and a dimethyl quinacridone resulting in the formation of a pure a-phase structure. Such procedure allowed the comparison of both the crystal structure and the morphology of the copolymer. For the ß-nucleated copolymer a maximum of the k-value (fraction of ß-phase) was found for a concentration of the nucleating agent of 5 × 10−4 wt.-%. By means of the WAXS measurements (in the transmission and reflection mode) an important structure gradient was detected in the cross-section of the injection moulded samples. This structure gradient was also observed by optical microscopy, where an agreement between optical observation of the spherulites and the k-value distribution on the cross-section of the samples was observed. For both nucleating agents (linear transquinacridone and dimethyl quinacridone) a dependence of the mechanical properties of the copolymer (modulus of elasticity and brittleness by impact resistance) on the pigment concentration was observed. For the ß-phase nucleated copolymer the maximum of the k-value of the hexagonal crystal structure corresponds to the highest ductility by impact test.
The Role of Long Molecules and Nucleating Agents in Shear Induced Crystallization of Isotactic Polypropylenes**
Authors: Jerschow P. , Janeschitz-Kriegl H.
Published: December 2013

Short term shearing at low degrees of supercooling with subsequent monitoring of the crystallization process of iso-tactic polypropylenes leads to highly oriented surface layers and fine grained layers that reach further into the core of the solidified samples. This process is highly dependent on the content of long polymer chains or nucleating agents. The present paper shows a first experimental evidence for these facts together with theoretical considerations. If long polymer chains are present, as it is the case in reactor grades of iPP, shear induced crystallization is more sensitive to shear treatment. As a consequence, the orientation of the surface layers is much higher in these materials. Additionally, the surface layers – both, highly oriented and fine grained – are more distinct and, therefore, allow an easier quantitative determination. If the materials contain nucleating agents, highly oriented layers occur in materials containing long polymer chains as well as in rheology controlled grades. A first theoretical description of the possible role of nucleating agents is given.
Simulation of Non-Isothermal Flow in a Modular Buss Kneader and Comparison with Experiment
Authors: Lyu M.-Y. , White J. L.
Published: December 2013

Non-isothermal flow is simulated in a modular Buss Kneader including crosshead screw extruder. A method of calculating cycle averaged mean temperature rises for individual elements is discussed and results are presented. A method is then described for making calculations in a modular multi element Buss Kneader. Finally we compared the calculations with experiment.
New Aspects Concerning the Design of Coathanger Dies
Authors: Peiffer H. , Dietz W.
Published: December 2013

This work covers a new model to compute flat dies for the production of biaxially oriented polypropylene film. The computational model was developed in the late eighties and is particularly suited for dies of high throughput and width. In the development of new dies for our production lines, it was realised that all models known at the time we began this work had failed. These models only accounted for viscous flow in the die channels under ideal conditions. Temperature differences in the melt and the elastic behaviour of the die walls were not accounted for in those models. The new model allowed us to design dies for high throughput with no difficulties. With the model we were now able to provide our production with dies of optimal design. Before the model is explained in detail, the production process for biaxially oriented polypropylene film is sketched and the market demand for such films is explained.
Determination of the Inter-Relationships Between Processing Conditions and Properties of an Injection Molded Silicone Ring Using an Experimental Design
Authors: Barbaroux M. , Stalet G. , Regnier G. , Trotignon J.-P.
Published: December 2013

The effects of injection-molding parameters on the mechanical-physical properties of a liquid silicone rubber (LSR) injection-molded ring were studied through an experimental design. The effects of the changeover point (volume or pressure driven), runner (hot or cold), hold pressure, mold temperature and injection flow rate variations were evaluated based upon the responses related to both material properties (ultimate elongation and tensile stress in a tensile test, swelling in hexane, hardness, density) and ring properties (cross sectional diameter, weight, volume). It was determined that ring density is not dependent on the parameters studied. The mold temperature appeared to be a very influential parameter, especially concerning material characteristics: it affects the swelling ratio, hardness, and ultimate properties, but weight and volume are only affected when the cold runner is used. The hold pressure has an effect on both the weight and volume of the ring. The type of changeover used (volume or pressure) has no effect when a cold runner is used, but affects the weight, volume, and ultimate properties of the ring, when a hot runner is used. The injection flow rate did not affect the observed characteristics.
Numerical Simulation of the Flow and Fiber Orientation in Reinforced Thermoplastic Injection Molded Products
Authors: Kabanemi K. K. , Hétu J. F. , Garcia-Rejon A.
Published: December 2013

This paper describes a fully three-dimensional transient finite element method for calculating the flow behavior and fiber orientation during filling of injection molded parts. The fiber-fiber interaction is taken into account. The momentum and continuity equations are first solved with the viscoelastic stress treated as a fixed body force. The kinetic equation for the orientation tensor is then integrated with known kinematics using the standard Galerkin method. The calculation is performed on a time-dependent flow domain. Since the method is truly three-dimensional, singular regions such as the flow front or near injection gates and solid boundaries, where decoupled approximations are not valid, are naturally dealt with. The material anisotropy behavior is modeled by using the Doi-Doraiswamy-Metzner model. Numerical results, involving the Poiseuille flow and the filling of an end-gated plate, emphasizing the importance of the three-dimensional coupling calculations between the flow and orientation are presented.
Comparison between LDPE Conventional and Autothermal Extrusion Characteristics
Authors: Sikora J. W.
Published: December 2013

In the paper, a characterization of autothermal and conventional extrusion processes of low density polyethylene (LDPE) in the typical single screw extruder equipped with a classical screw was presented. It was shown that autothermal (adiabatic) extrusion process is characterized by better effectivity factors than a conventional extrusion process carried out in the same basic extrusion conditions. In both processes the mass flow rate, total extruder power, total energy consumption per unit mass, extruder energy efficiency, extrusion velocity, temperature distribution along the plasticating system and extruder head, were compared. The attempt to present shear stress and flow rate distribution during laminar and isothermal flow of the non-Newtonian fluid through the circular channel (extrusion die) was undertaken. Appropriate dependences of experimental factors on the rotational speed and angular frequency of the screw were made. Appropriate conclusions were drawn.
Comparative Study of Structure Development in Melt Spinning Polyolefin Fibers
Authors: Choi C.-H. , White J. L.
Published: December 2013

A comparative study of crystallization and orientation development in melt spinning is presented for four polyolefins: high density polyethylene (PE), polypropylene (PP), polybutylene (PB-1), and poly-4-methylpentene-1 (P4MP). The purpose was to compare the behavior of two relatively unknown polyolefins PB-1 and P4MP with the much better known and characterized PE and PP. Melt spinning was carried out at different temperatures. Melt spun filaments were characterized by wide angle x-ray diffraction (WAXS), birefringence and differential scanning calorimetry (DSC) measurements. Polymorphism (multiple crystalline states) is noted in the filaments of polybutylene which exhibits aging from one form to another as well as in polypropylene. Careful attention is given to heat transfer during cooling. The orientation of flexible chains in the melt state is well known to be determined by the stress field. The crystalline orientation of the solidified crystalline filaments as a function of spinline stress is found by WAXS to be highest for the P4MP and lowest for the PE. Birefringences of the melt spun PE fiber are however higher than PP or PB-1 and P4MP which had the lowest values when comparisons are made at the same spinline stress. However if intrinsic birefringence was used, the data order the same as the WAXS results.
Experimental Validation of Shrinkage Predictions for Injection Molded Products
Authors: Jansen K.M.B. , van Dijk D.J. , Burgers E.V.
Published: December 2013

Two injection moulding simulation codes (C-MOLD of AC Technology and VIp of Eindhoven University) are compared with experimental results regarding cavity pressure and product shrinkage. It turns out that the cavity pressure profiles are only moderately well predicted by both codes. The shrinkage predictions can be considered as a post processing step with temperature and pressure fields as an input (the so-called thermoelastic model). It is shown that the shrinkage predictions agree well with the measurements using the thermoelastic model with actual pressure profiles as an input. Direct simulation of product shrinkages resulted in an overprediction of shrinkage.