bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of the Cooling of Semi-crystalline Polymers during their Processing
Authors: Billon N. , Barq P. , Haudin J. M. 
Published: December 2013

Abstract
As a first step for the modelling of the processing of semi-crystalline polymers, it is proposed a new overall kinetic model which allows to calculate the evolution of the transformed volume fraction whatever the cooling conditions are. This model derives from initial Avrami-Evans' theory. The transformed volume fraction is calculated as a function of parameters which are measured during crystallizations at a constant cooling rate. This model is easy to use and can be introduced into a more complete thermomechanical calculation. For this purpose we propose to express the energy equation in terms of the enthalpy function. Two applications of our model are presented: the cooling of a polymer sheet (non-flowing polymer) and the cooling of the film on the chill-roll during the cast film extrusion process (flowing polymer).
Model Development for an Internal Mixer
Authors: Meissner K. , Poltersdorf B. 
Published: December 2013

Abstract
Using the relevance and importance modelling the mixing process in an internal mixer as a starting point, the physically based modelling of the mixing process will be discussed. There are three essential aspects of model development, i.e. the geometric model, the selection of relevant rheological properties and the establishing of relevant balance equation terms. Various models will be discussed and evaluated on the basis of literature and our own work.
The calculated field quantities can be used to determine the internal mixer's action quantities (e.g. deformative mixing effect, dispersing effect, thermomechanical load etc.) and to set up suitable working diagrams.
Thermo-viscous Effects in Extrusion of Planar Jets with Solidification
Authors: Alexandrou A. N. , Torikoglu G. 
Published: December 2013

Abstract
The present work is a study of the thermo-viscous effects in the extrusion of a “power law” liquid with temperature dependent viscosity by including the effects of solidification. This is achieved by using a novel inverse isotherm finite element method. The method is based on an inversely defined (but not inverted) formulation where the isotherms are characteristic transverse coordinate lines. The method allows the simultaneous evaluation of all the field variables as well as the apriori unknown geometric parameters. It is shown that under certain conditions the extrudate can be significantly affected by the presence of the solidification front. Results are presented for die-swell, pressure, and location of solidification as a function of the material properties.
Crystal Orientation in Injection Moldings of Flaky Filler-Filled Polypropylenes
Authors: Fujiyama M. 
Published: December 2013

Abstract
Crystal orientation states in injection moldings of polypropylenes filled with flaky fillers such as glass flake, mica, and talc have been studied. Talc-filled polypropylene injection moldings show a peculiar crystal orientation, in which the plate planes of talc particles are aligned parallel to the mold surface, the c- and a'-axes of polypropylene crystals are bimodally oriented to the flow direction, and the b-axes are oriented in the thickness direction. Although an unfilled polypropylene injection molding basically shows a similar crystal orientation to that of the talc-filled polypropylene injection molding, the b-axis orientation to the thickness direction is much weaker. Glass flake- or mica-filled polypropylene injection moldings show similar crystal orientations to that of the unfilled polypropylene injection molding. Only talc-filled polypropylene injection moldings show the peculiar crystal orientation. Since an injection molding of polypropylene filled with only 0.5 wt.-% talc already shows the peculiar crystal orientation, it is assumed that talc influences a remote interaction on the crystallization of polypropylene.
Mixing History on the Morphology and Properties of Thermoplastic/LCP Blends
Authors: Sukhadia A. M. , Datta A. , Baird D. G. 
Published: December 2013

Abstract
Blends of poly(ethylene terephthalate) (PET) and polypropylene (PP) with several liquid crystalline polymers (LCPs) were successfully generated using a novel blending method, referred to as the dual-extruder mixing method. In this method, the matrix and LCP polymers were plasticated separately in two single-screw extruders. The melt streams were then joined together and blended in a Kenics static mixer containing 18 mixing elements. Strands (rods) and sheets of the blends were extruded using the above method. First, blends of thermoplastics with LCPs were successfully made using this method in which there is little or no overlap of the nominal processing temperatures. Second, the morphology of extruded strands from the dual-extruder mixing method was seen to consist of LCP fibrillar structures which were truly continuous running the length of the extrudate and further devoid of any skin-core type structure. Third, LCP fibril formation was seen to occur even when the LCP concentration was only 4 wt.-% in the blend. By contrast blends from the single-screw extrusion exhibited a distinct skin-core fibril-droplet type of structure.
Finite Element Simulation of Plug-assist Forming
Authors: Song W. N. , Mirza F. A. , Vlachopoulos J. 
Published: December 2013

Abstract
A thick sheet analysis of deformation is used to simulate the process of plug-assist forming. The formulation is based on the total Lagrangian description and the equations are solved by the finite element method. The results are in agreement with experimental data available in the literature for sheet thickness distribution and plug force required as a function of deflection. The analysis provides the complete stress and strain fields and may be used to locate regions where fracture may initiate.
Experimental Study of High Reynolds' Number Flows Between Narrow Gaps
Authors: Cohnen W. , Osswald T. A. 
Published: December 2013

Abstract
High Reynolds' number flows between narrow gaps are very common in the reaction injection mold filling process (RIM) where low viscosity polymers are injected into thin mold cavities in relatively short time intervals. The resulting short cycle times have given RIM advantages over other manufacturing techniques in the polymer industry. In addition to the lower temperatures encountered during the RIM process, the low material viscosities enables mold filling using smaller injection pressures and mold clamping forces than in the conventional thermoplastic injection mold filling process. Considering the low viscosity of the injected fluid, short injection times and considerably large parts, such as automotive body panels, it is clear that in RIM processes inertia effects are not negligible. In fact Reynolds' numbers in such processes can reach 10 and above. This paper presents an experimental study performed on the high Reynolds' number flows between narrow gaps. First, the general equations that govern such flows are derived and written in dimensionless form. The magnitudes and influence of inertia forces, surface tension and viscous forces are analyzed in terms of Reynolds' number, capillary number and Weber number. The theoretical background is followed by a short explanation of the experimental set-up. Several experiments are shown in different mold configurations and at various mold filling speeds. The results showed that inertia greatly influences the mold filling pattern and capillary effects are a major cause of air bubble entrapment.
Structures and Properties of Injection Moldings of Flaky Filler-filled Polypropylenes
Authors: Fujiyama M. 
Published: December 2013

Abstract
A polypropylene was filled with 0 to 30 wt.-% of flaky fillers such as glass flake, mica, or talc, which had similar particle sizes and different aspect ratios and crystallization temperatures. Flexural test specimens were injection-molded from the filled polypropylenes at cylinder temperatures of 200 to 320°C. Properties such as flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, and mold shrinkage and higher-order structures such as crystallinity, β-crystal content, thickness of skin layer, a'-axis-oriented component fraction, and crystalline orientation fraction were measured and structure-property relationships were studied. A simulation of molecular orientation was carried out from a viewpoint of melt orientation at the gate and its relaxation in the mold cavity.
Non-isothermal Crystallization of a Polymer Film on Chilling Rolls
Authors: Malkin A. Y. , Baranov A. V. 
Published: December 2013

Abstract
The problem of heat exchange and non-isothermal crystallization of a polymer film (leaving an extruder) on the surface of chilled rolls is discussed. Factors such as enthalpy of crystallization, unsymmetric boundary conditions and dependences of thermal properties of a polymer on temperature and degree of crystallinity are taken into account.
The statement of the problem is based, first, on joint analysis of non-stationary energy balance equation and kinetics of non-isothermal crystallization and, second, on inclusion of dependences of thermal properties of a polymer on temperature and crystallinity into a mathematical model under discussion.
The influence of technological and engineering factors on the quality of film is discussed.
Estimation of Quality of Mixing
Authors: Malkin A. Y. , Baranov A. V. , Viculencova M. E. , Prokhorova L. N. , Sivetskii V. I. 
Published: December 2013

Abstract
The character of mixing was interpreted through the energy consumption. It was correlated with the quality of mixing which is described by two parameters: average degree of dispersion and coefficient of heterogeneity. Experiments were carried out for polyethylene-based compounds with various fillers and typical rubber compound with carbon black. In the first case the general dependence of degree of dispersion upon the work of mixing for different fillers was obtained. In the second case common dependence for diverse technological regimes of mixing was also observed. In both cases these dependences were very close to exponential functions. It was demonstrated that the quality of mixing influences the performance characteristics (yield stress and deformation at break) of compositions of polyethylene with solid fillers.
Extrusion of Recycled Polymer Feedstocks
Authors: DiRaddo R. W. , Nguyen K. T. , Garcia-Rejon A. 
Published: December 2013

Abstract
The increased emphasis on the use of recycled feedstocks has brought in the need for continuous on-line monitoring of process conditions. This is done in an effort to detect process shifts and react accordingly to maintain optimal conditions. Time series analysis is ideal for on-line modelling of continuous processes employing recycled feedstocks, as the disturbances present in the feedstock can be quantified using this approach. The models obtained can then be employed for closed loop control of the process. The closed loop control allows for maximizing of the amount of recycled material, yet ensuring an acceptable finished product.
This work presents a study of the stochastic dynamics of the extrusion of recycled feedstocks. Both “in-house” and “post-consumer” feedstocks are considered. Process outputs include the extrudate thickness and diameter, the head pressure, the melt temperature and the flowrate. The process inputs are the die gap and the level of recycle material. Process and disturbance transfer function models are obtained.
Control simulations are performed on the process and disturbance models to ascertain the feasibility of a closed loop system for maintaining of optimal process conditions. A minimum variance controller (MVC) is employed in the simulation. The response of the closed loop system to various disturbance inputs is monitored. The control scheme results in a much lower offset from the set point for the case with MVC than for the case with no control.
Theoretical and Experimental Investigations into Screws for Extruding Polypropylene
Authors: Peiffer H. , Dietz W. 
Published: December 2013

Abstract
In the processing of polypropylene via a melt, the extruder exerts an important influence on product quality. Trials were carried out on production extruders with the aim of improving melt quality. As an aid to evaluating the screws, a computer model was developed which could simulate extruders. This model is described in the first part of this paper. In the second part, the computer model is tested using experimental data taken from a range of different extruders. The comparisons illustrate the excellent correlation and hence validity of the model. On the basis of these results, recommendations are given for the optimization of single-screw extruders.
Melt Spinning Effects on Optical and Mechanical Properties of Poly(Aryl Sulfone)
Authors: Yilmaz F. , Çakmak M. 
Published: December 2013

Abstract
Poly(aryl sulfone) belongs to a group of polymers with a very low crystallizabilities which include polycarbonates, polyether imide and polyarylate. When subjected to high temperature gradients in such processes as injection molding and melt spinning, this class of polymers vitrify into glassy form. However their processing-property relationships are quite different from those conventional amorphous materials such as atactic polystyrene (a-PS) and atactic poly (methyl methacrylate) (a-PMMA). These new polymers being already highly ductile materials do not undergo brittle-ductile transition when oriented beyond a critical orientation levels which is typical of a-PS and a-PMMA. The chemical structure of poly(aryl sulfone) chain is mainly composed of para linked phenyl groups and this gives rise to high optical anisotropy in the chain. With small levels of orientation large optical birefringences are attained in the fibers. This polymer was also found to obey the stress optical law which states that there is a linear relationship between the stress at the vitrification and the birefringences developed in the fibers. Beyond a critical stress level around 108 dynes/cm2 deviation from this linearity is observed. This deviation from linearity may possibly be related to onset of structural ordering that takes place at high orientation levels. The mechanical properties were found to correlate quite well with the spinline stress and modulus, yield stress and tensile stress were found to increase and elongation at break was found to decrease with increasing orientation.
Melt Strength Behaviour of Polypropylenes
Authors: Ghijsels A. , De Clippeleir J. 
Published: December 2013

Abstract
Melt strength data are presented for polypropylenes, differing widely in molecular weight and molecular weight distribution. Melt strength was assessed from uniaxial tensile experiments with a Rheotens apparatus. A new measuring procedure was applied by performing the stretching in front of the take-up wheels of the Rheotens instead of in between the wheels. It is shown that the melt strength of polypropylene is solely determined by its weight average molecular weight. At a given melt index level, narrow molecular weight distribution (controlled rheology) polypropylenes have a lower melt strength than the wider distribution reactor grades. At high temperatures, the melt strength follows an Arrhenius type temperature dependence, while at the lower test temperatures the melt strength of polypropylenes having a wider distribution is increased by flow-induced crystallisation.
Thermal Effects in Extrusion: Slit Dies
Authors: Pittman J.F.T. , Sander R. 
Published: December 2013

Abstract
A mathematical model is set up for melt flow and heat transfer in a slit die, coupled with heat transfer in the die body. The model is reduced to two dimensions by neglecting variations across the width of the die. Conduction, convection and viscous dissipation in the non-Newtonian melt are included, together with conduction and electrical heating in the die body and heat losses by free convection and radiation from the die surfaces. The model is implemented using finite elements, and provides detailed temperature fields on the die cross-section, displaying, for the first time, the effects of thermal coupling between the melt and die body. The consequences for processing are discussed for several situations, including horizontal and vertical operation of the die, with a polished or corroded surface, and with or without insulation. The appropriate use of dimensionless groups for the interpretation of the numerical results is discussed. A criterion in terms of a Pearson number is developed, for assessing whether an isothermal melt flow analysis is applicable. A simple analytic result is proposed for calculating the die set temperature required to minimise melt temperature variations. This is tested against the numerical results and is broadly validated.
Functionalization of Polypropylene with Maleic Anhydride by Reactive Extrusion
Authors: Martínez J. Ma. Ga. , Taranco J. , Laguna O. , Collar E. P. 
Published: December 2013

Abstract
This paper describes first results obtained in our group on the study of the reactive extrusion process for maleation of polypropylene in the presence of a radical initiator (peroxide).
In accordance with the conclusions obtained in a previous paper the viability of such reactive processing is confirmed. Furthermore the necessity of a careful study about the values of the experimental process conditions in order to know the set of conditions which maximize the grafted maleic anhydride into the polypropylene, can be clearly concluded.
We observe that the same mechanism seems to be governing the grafting reaction in the continuous and in the batch process. This can clearly be concluded from the results shown in this paper and in previous work.
Solids Transport in Extruders
Authors: Campbell Gregory A. , Dontula N. 
Published: December 2013

Abstract
A new analysis of the solids conveying of single screw extruders and solids feeders is developed. The new analysis is based on an assumption that the solids are pushed up the barrel by the flights on the screw. The new analysis when tested on literature data was found to be in qualitative agreement with all ratios of screw to barrel friction factor of the polymeric materials reported.
Flow Implications in the Processing of Tetrafluoroethylene/Hexafluoropropylene Copolymers
Authors: Rosenbaum E. E. , Hatzikiriakos S. G. , Stewart C. W. 
Published: December 2013

Abstract
The melt fracture behavior of two Teflon® resins was studied in capillary extrusion in order to identify the critical conditions for the onset of melt fracture and wall slip. These resins were copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) and TFE/HFP/PAVE (perfluoro (alkyl vinyl ether)) (PAVE) respectively. The incorporation of the third monomer in the molecules of the resin was found to improve the processability of polymer without substantially changing its rheology. Surface melt fracture (sharkskin) appeared at wall shear stresses greater than about 0.18 MPa, practically independent of temperature in the range of 300 to 350°C. At higher apparent shear rates oscillating melt fracture was observed due to the presence of wall slip and compressibility of the melt. Furthermore, a superextrusion region was identified at apparent rates greater than about 700 s−1, beyond those where oscillating melt fracture was obtained. In this region, the extrudate appears again smooth. Finally, it was found that the addition of 0.1 % of polyethylene in the resins, reduces dramatically the pressure drop along the capillary die and eliminates extrudate distortion over the whole range of apparent shear rates up to the superextrusion region.
Measurement of Planar Orientation of Fibers for Reinforced Thermoplastics Using Image Processing
Authors: Yaguchi H. , Hojo H. , Lee D. G. , Kim E. G. 
Published: December 2013

Abstract
The characteristics of fiber-reinforced thermoplastics depend on the quantity and shape of fibers. The fiber-matrix separation and fiber orientation are caused by the flow during a molding process. Then, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation-orientation and molding conditions. In this paper, we propose the measurement method which is called image intensity method for fiber orientation distribution by image processing. In order to examine the accuracy of intersection counting and image intensity methods, the fiber orientation of simulation figure is measured using image processing. The image intensity method is rather accurate compared with the intersection counting method.
Microporous Film, Made from β-Crystalline Phase Polypropylene
Authors: Shi G. , Zhang X. , Zheng J. , Zhou G. 
Published: December 2013

Abstract
A new type microporous polypropylene film was prepared simply by biaxial drawing of β-crystalline phase polypropylene The effect of draw ratio on the pore size distribution, ethanol sorption, and porosity, as well as β-α transformation during drawing were studied For the purpose of improving its hydrophilicity ion and solute permeability, the plasma graft-polymerization technique was utilized The resulting film showed much higher permeability toward Na+, Mg++ and urea, being 3.2 × 10−6, 5.8 × 10−8 and 1.75 × 10−6 cm2/min, respectively, than the original one and had better dimensional stability.
Cooling Process Window Development for Injection Molding
Authors: Xie B. , Bigio D. 
Published: December 2013

Abstract
The great impact of the injection molding cooling process on both productivity and product quality makes it essential to optimize the cooling conditions as well as the cooling system design. The current practice in injection molding process development, to identify the final operating conditions, which is a time consuming iteration between model design and product line, is costly in both material and time. This defect in the process development also raises the necessity to establish a method, which can provide the manufacturer not only with an optimum but also with a window around the optimum for the operating conditions, so as to avoid this time with consuming process to determine the feasible operating conditions. This paper presents a methodology, which combines an optimization algorithm with a mold cooling analysis, to obtain an optimal cooling processing condition and a cooling window in the injection molding of plastics as an aid for mold designing and manufacturing. The cooling effect, which is characterized through uniform cooling and short cooling time, is quantified in terms of mold cooling simulation output. A mathematical model is then formulated based on semi-empirical criteria and solved numerically by implementing an optimization algorithm. Based upon the resultant final optimum cooling condition, a relaxation scheme scheme is developed by the authors and performed, followed by a sensitivity analysis to determine the cooling window. At last, the application of this method is demonstrated by two industrial molds: a drilling housing and a compact drill battery pack. This approach will help in designing a proper cooling system for a mold and in determining an operating range to achieve better part quality and higher productivity.