bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Limitations of Shear Induced Crystallization in Polypropylene Melts
Authors: Liedauer S. , Eder G. , Janeschitz-Kriegl H. 
Published: December 2013

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.