bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Simulation of Multi filament Air Jet Melt Spinning
Authors: Ishihara H. , Hayashi S. , Ikeuchi H.
Published: December 2013

Air jet melt spinning for multifilament system was studied both theoretically and experimentally. Basic equations describing the multifilament system of air jet melt spinning were derived by considering air temperature and velocity of cooling flow surrounding the individual spinlines. Numerical computations of the fundamental equations for air jet melt spinning were carried out for various spinning conditions. Steady-state solutions obtained give the spinline cross sectional area, spinline temperature, spinning tension and spinline velocity. These are described as a function of the distance measured downward from the spinneret. Air jet melt spinning experiments were conducted for poly-(ethyleneterephthalate) (PET) having an intrinsic viscosity of 0.61. The spinning variables were changed mainly in terms of throughput, distance from spinneret point to ejector and air pressure in the ejector. Good correlations between theory and experiment were obtained for the final spinline speed or as-spun fiber denier. Further, the molecular orientation of asspun fiber can be estimated using the computed stretching speed at the ejector point. It was found that the simulation program of multifilament air jet spinning is very useful in finding the appropriate spinning conditions for the industrial spinning process and in estimating fiber properties.
Cast Film Extrusion of Polypropylene Films
Authors: Cotto D. , Duffo P. , Haudin J. M.
Published: December 2013

In cast film extrusion, the polymer melt is extruded through a slit die, slightly stretched in air and then cooled on a chill-roll. An important part of the present work was devoted to the development and application of a thermomechanical model of stretching in air and of a purely thermal model of cooling on the roll, taking polymer crystallization into account. The structures and morphologies in a series of extruded polypropylene films were investigated using density and sonic modulus measurements, wide-angle X-ray diffraction, small angle light scattering and optical microscopy. These experimental results combined with theoretical predictions obtained from the model allow to discuss the respective effects of stretching in air and cooling on the roll. Stretching in air essentially affects spherulite nucleation and growth during subsequent crystallization on the roll. Dissymmetrical cooling on the roll induces an inhomogeneous microstructure within the film. The presence of a zone with a finer microstructure near the roll has been correlated with the cooling rates and thermal gradients calculated by the model.
Prediction of Birefringence for Optical Memory Disk
Authors: Kanai T. , Shimizu K. , Uryu Y.
Published: December 2013

Polycarbonate (PC) is considered to be a proper resin for optical memory disk, however PC resin shows high birefringence. It is very important to reduce birefringence of PC optical memory disk. This research is to obtain the relationship between birefringence and process conditions and to get the optimum condition for the production of low birefringence substrate of PC optical memory disk. The birefringence distribution of PC optical memory disk was theoretically predicted by the calculations of both the stress distribution caused by molecular orientation during the filling stage and the thermal stress caused by temperature difference during the cooling stage. The relationship between birefringence distribution and the process conditions such as rheological properties of PC resin, injection temperature, mold temperature, mold design and annealing condition is possible to be predicted theoretically by calculating shear stress during the injection process and thermal stress during the cooling process. The predicted results of birefringence distribution qualitatively agree with the experimental ones.
Experimental Investigation of Rotational Molding and the Characterization of Rotationally Molded Polyethylene-Parts
Authors: Iwakura K. , Ohta Y. , Chen C. H. , White J. L.
Published: December 2013

An experimental study of the rotational molding of polyethylene parts is presented. Specific attention is given to heating and cooling of the molding cycle and to the micro structuring and bulk characteristics. Experimental measurements of the heatup of the oven at the startup of the process is presented. The heatup of different molds in the oven is then measured and interpreted in terms of heat conduction theory and the Fourier number αt/L2. In the experiments, thick aluminium molds heated up more slowly than thinner steel molds. The cooling characteristics of mold subject to different quenching conditions were compared with water showers inducing the most rapid cooling followed by fan blowing and the slowest being in quiescent air. The order of cooling of the different molds studied followed the same order as their rates of heating as would be expected from the theory of heat conduction. Polyethylene parts formed in the molds were found to be crystalline, without orientation and to possess large spherulites. The size of the spherulites and the level of the crystallinity was highest where the cooling rate was the lowest. Uniformity of part thickness and warpage were measured. Warp age correlated with rapidity of cooling rate. This suggested a mechanism of thermal quench stresses.
Fabrication of Microstructures of Extreme Structural Heights by Reaction Injection Molding
Authors: Hagmann P. , Ehrfeld W.
Published: December 2013

For the fabrication of microstructures with minimum lateral dimensions in the micrometer range and structural heights of up to several hundred micrometers a new microfabrication technique has been developed by the Karlsruhe Nuclear Research Center. The so-called LIGA method is based on a combination of deep-etch X-ray-lithography, electroforming and plastic molding. High-quality micromold inserts can be prepared by deep-etch X-ray lithography and electroforming allowing an arbitrary choice of cross section of the microstructures. By optimization of the process parameters of the reaction injection molding process using casting resins on a methyl methacrylate base it has been shown that a yield of 100% can be achieved. For molding microstructures without any flaws, the mold material has to be degassed, the cavity of the mold must be evacuated and the shrinkage due to polymerization has to be compensated by applying a holding pressure. With an internal mold release agent which is a special salt of an organic acid, cycle times of about 12 min have been achieved in the micromolding process step which are very much shorter than the exposure and development times in the direct lithographic production of microstructures. Such plastic structures can represent the final product or, if microstructures are to be made of metal, they are used as templates in a subsequent electroforming process. Depending on the geometrical configuration of the microstructures, either a metallic gate plate or an electrically conducting plastic layer are used as the electrode for electroforming.
Non-isothermal Extrusion of Composite Materials
Authors: Alexandrou A. N. , Papanastasiou T. C.
Published: December 2013

Non-isothermal extrusion, of non-dilute fiber suspensions with solidification is analyzed by means of an integral constitutive equation for melt fiber suspension and a novel, streamlined inverse finite element method (IIFEM), to account for the solidification. Newton iteration is used to solve simultaneously the highly non-linear system of intergrodifferential equations for all the primary unknowns including the apriori unknown location of the solidification front and the free surface. The fiber orientation is computed using the orientation distribution function along selected streamlines of the melt suspension. It is shown that the final frozen-in orientation of the fibers in the resulting solid composite depends on the location of the solidification front. Thus by controlling the location of the solidification front by means of the flow, cooling rate and the capillary design may be possible to produce composites of several orientation patterns.
Optimal Cure Cycle Design for the Fiber Reinforced Composite Lamination Processing
Authors: Hou G. J. W. , Hou T.-H. , Sheen J. S.
Published: December 2013

Fiber-reinforced composite laminates are used in many aerospace and automobile applications. The magnitudes and durations of the cure temperature and the cure pressure applied during the curing process have significant consequences for the performance of the finished product. The objective of this study is to exploit the potential of applying the optimization technique to the cure cycle design. Using the compression molding of a filled polyester Sheet Molding Compound (SMC) as an example, a unified Computer Aided Design (CAD) methodology, consisting of three uncoupled modules, (i.e., optimization, analysis and sensitivity calculations), is developed to systematically generate optimal cure cycle designs. Various optimization formulations for the cure cycle design are investigated. The uniformities in the distributions of the temperature and the degree of cure within the specimen cured under the optimal cycles are compared with those resulting from conventional isothermal processing conditions with pre-warmed platens. Recommendations with regards to further research in the computerization of the cure cycle design are also addressed.
Flow Analysis in an Internal Mixer
Authors: Yagii K. , Kawanishi K.
Published: December 2013

An attempt has been made to predict flow behavior of the rub bery material in an internal mixer by means of finite element analysis. For the convenience of analysis, a simplified model for the mixer and some assumptions were introduced. The model consists of a circular cylinder and a rotor with uniform cross sectional shape along the axis which rotates around the axis located at the center of the cylinder. Rubbery material fills the void between the cylinder and the rotor. The assumptions are: the material is a power law liquid, the material is incompressible, and the viscosity is large enough to allow laminar flow.
Processing of ABS Latex in a Single Screw Extruder
Authors: Ghosh A. K. , Lindt J. T.
Published: December 2013

The feasibility of the continuous and direct conversion from latex to wet crumb through the coagulation process in an extruder has been demonstrated through this work. The coagulation efficiency in the extruder has been largely governed by temperature. The maximum rate of increase of the first and the second moments of the particle size distribution of the coagulated latex occur in the neighborhood of the polymer glass transition temperature. The particle densities showed no longer a one-to-one relationship to the specific surface typical of the batch coagulation experiments, as the material coagulated in the extruder did not reach the same degree of equilibrium. Although the basic trends remained the same as in the batch coagulation experiments, the addition of residence time distribution, inherently associated with the extruder operation, introduced some significant changes into the coagulation process.
Fibre Orientation Mechanisms for Injection Molding of Long Fibre Composites
Authors: Bailey R. , Rzepka B.
Published: December 2013

The development of skin/core fibre orientations in injection molded fibre reinforced compounds is considered, and the applicability of the Tadmor fountain-flow mold filling mechanism to long fibre reinforced is investigated. A disc and plaque mold cavity are used to consider the influence of each injection molding cycle parameter upon the skin/core structure. The influence of the flow path length is also considered. The independent orientation controlling mechanisms identified (the injection speed, melt temperature and the holding pressure cycle all of which influence the fibre orientation favourably) can be used in combination to achieve a optimised microstructure for the cavities under study.
Effect of Thermal History on Viscoelastic Properties of Thermotropic Liquid Crystalline Copolyesters
Authors: Masuda T. , Fujiwara K. , Takahashi M.
Published: December 2013

Dynamic viscoelastic properties of two samples of co-polyesters, PHB60 and PHB28, were measured over a wide range of temperatures. The copolyesters had been synthesized from polyethylene terephthalate (PET) and p-hydroxybenzoic acid (PHB). PHB60 and PHB28 contain 60 and 28 mol.-% PHB as the comonomer, respectively. PHB60 is well known as a thermotropic liquid crystalline copolyester. The effect of thermal histories on viscoelastic behavior of the copolyesters are discussed in terms of structure and liquid crystallinity of the copolyesters. A rheological transition in viscoelastic properties of the copolyester PHB60 was observed at about 270°C in the fluid state. The viscoelastic properties of the copolyester PHB60 strongly depend on thermal histories below the transition temperature, but not above the temperature. The transition behavior was attributed to a crystal-nematic transition by wide angle X-ray diffraction and differential scanning calorimetry. The attainable crystallinity was fairly low. Thermal history behavior found below the transition temperature is caused by slow crystallization and supercooling of the sample. PHB28 forms no liquid crystal phase, and is thermorheologically simple in the molten state: the sample showed no effect of thermal history in viscoelastic properties.
Molecular Orientation and Modulus of a Thermotropic Liquid Crystalline Copolyester
Authors: Fujiwara K. , Takahashi M. , Masuda T.
Published: December 2013

The relationship among processing parameters, molecular orientation, and modulus of a thermotropic liquid crystalline copolyester synthesized from poly(ethylene terephthalate) and 60 mol.-% p-hydroxybenzoic acid was systematically investigated so that the dominant processing factors to result in high orientation and high modulus were elucidated. Solid filaments were prepared by shear flow in capillaries and elongational flow by spinning from the liquid crystalline phase of the copolyester at various processing conditions. Superstructure, especially molecular orientation, of the filaments was analyzed by wide angle X-ray scattering (WAXS), scanning electron microscopy (SEM), and polarizing optical microscope (POM). Also, tensile modulus of the filaments was determined. Although filaments prepared by means of shear flow in capillaries had the Hermans orientation function of about 0.3, tensile modulus and morphology by SEM and POM did not exhibit the evidence of high orientation of the filaments even at high ratios of length over diameter and high shear rates. In the elongational flow by spinning, the dominant processing parameters for molecular orientation and increasing of tensile modulus are a spin-draw ratio and an initial diameter of the filament. The small diameter results in high orientation and high modulus. Enhancement of modulus was independent of the processing conditions related to a relaxation process of molecular orientation, such as spinning temperature, strain rate, and cooling. These results imply that there exists a size effect for the orientation process.
Frequency Analysis of Pressure Fluctuations in a Single Screw Extruder
Authors: Becker J. , Klason C. , Kubát J. , Sáha P.
Published: December 2013

This paper demonstrates the usefulness of frequency analysis in monitoring flow behavior in a single-screw extruder fitted with a capillary die with a length to diameter aspect ratio of 20. The melt pressure in the barrel and die was measured by a transducer, and the pressure fluctuations processed in a Fast Fourier Transform (FFT) frequency analyzer. The pressure fluctuations were studied under various processing conditions for high density polyethylene, linear low density polyethylene and polypropylene. In general, stable extrudate flow generates a noise spectrum with low intensity, the intensity increasing with the level of instability. The machine vibrations appeared to have a direct effect on flow stability. Also, unstable melting of the resin along the screw resulted in an increase in noise level. It seems probable that the frequency of the surface distortions can be related to the shape of the noise spectrum. In general, although more complex in nature, the noise results related to melt flow in the extruder were in agreement with data reported for capillary flow using a piston rheometer.
Modelling of the Cooling of Semi-crystalline Polymers during their Processing
Authors: Billon N. , Barq P. , Haudin J. M.
Published: December 2013

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

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

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

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

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

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

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

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

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

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

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.
Dimensional Control of Multicomponent Extrusion
Authors: Stevenson J. F. , Codispoti T. E. , Chung B.
Published: December 2013

This paper presents a patented method [1] for relating the output from individual extruders to measured external extrudate dimensions and then for using these dimensions to control individual screw speeds.
Theoretical and Experimental Investigations into Screws for Extruding Polypropylene
Authors: Peiffer H. , Dietz W.
Published: December 2013

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

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

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

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

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

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

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

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

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

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.
35 Years of Studies of Mixing of Rubber and Viscoelasticity
Authors: Nakajima N.
Published: December 2013

This paper provides a scientific treatment for mixing of rubber with reinforcing fillers. The primary attention is given to the viscoelastic nature of rubber. It is addressed to the practitioners of rubber processing, who have hands-on experience but lack familiarity with viscoelasticity. In the first part we provide a sketch of the major events: (1) polymerization, (2) resulting molecular architecture, (3) mechanical property of gum rubber, (4) mill processability, (5) processing with the internal mixer, and (6) compounding rubber with carbon black. The focal point of this paper is to relate the mill processability to the elongation and failure behavior of gum rubber. Viscous and elastic contributions to this relation are described. This relation provides the starting point for introducing scientific treatment for rubber mixing. Mechanisms of incorporation and dispersion of carbon black are also discussed. The presentation follows in an order of description on the behavior of gum rubber, that of carbon black, the interaction between rubber and carbon black, and the interaction between the material and the internal mixer.

In the second part a method of constructing viscoelastic master-curves from the tensile stress-strain data is presented. Such a master curve serves as a useful means of characterizing gum rubber in relating polymerization, resulting molecular architecture and processability. The milling and mixing of rubber with filler are achieved with fracture; the consequence of fracture is a generation of supermolecular flow units. The mechanism of fracture involves the pull out of chain ends through entanglements. The high concentration of the chain ends on the surface gives a tacky appearance to mixed compounds.
Morphology and Oxygen Barrier Properties of LDPE/EVOH Blends
Authors: Lee S.-Y. , Kim S.-C.
Published: December 2013

The morphology of the dispersed phase in immiscible polymer blends can have a significant effect on the final may be omitted physical properties. Laminar dispersion of an ethylene vinyl alcohol copolymer (EVOH) with high oxygen barrier properties was obtained in the matrix of low density polyethylene (LDPE) when extruded through an annular blown film die. A large range of morphology was observed and indicated that the main factors determining the morphology of the blends were the composition, the viscosity ratio of the components, the processing conditions, and the elongational fields at the exit of the die. Increasing amount of EVOH (from 5 to 20 vol %) resulted in increasing number of stacked layers. Highly elongated laminar structure was formed when the viscosity ratio (ηd(EVOH)/ηm
(LDPE)) was close to one and slightly lower. Large predeformed domains in the extruder outlet (before drawing and blowing) with short residence time under high screw rpm and lower viscosity ratio in the die temperature favored the formation of well-developed laminar structure. Oxygen permeation tests have shown high barrier effects due to the formation of the laminar dispersion which acted as barriers to the permeant molecules by providing a long tortuous path.
Viscous-Elastic Effects in a PA 6 Melt – Cause of Unevennesses in Melt-Spun Yarns**
Authors: Beyreuther R.
Published: December 2013

The paper deals with dynamic investigations for qualitative and quantitative estimation of the transition behaviour of a PA 6 melt spin equipment in the velocity range of 2 500 to 4 000 m/min. On-line measured time functions of yarn tensile force, yarn fineness and yarn tension, which are caused by determined spinning pump revolution number changes, have been evaluated to estimate the length of disturbed yarn with changed properties. Between spinning pump disturbances and the resulting yarn quality disturbances the delay time constant could be estimated with a typical size of about 1 s. Some hundred meter of yarn are disturbed in their properties during such a transition process. The main cause for the delayed cause-effect-transition could be found in the compression modulus of the melt between the spinning pump and the spinneret. The described dynamic step investigations permit to use a spinning equipment as a measuring system to estimate the compression modulus of melt spinnable polymers.
The Crystallinity of PVC and its Effect on Physical Properties**
Authors: Bao Y. , Weng Z. , Huang Z. , Pan Z.
Published: December 2013

Differential scanning calorimetry (DSC) was used to investigate the crystallinity of crude PVC powders and annealed PVC compounds. Crude PVC powder exhibited a broad crystallite fusion endotherm ranged from 110°C to 220°C. High degree of polymerization of PVC showed high degree of crystallinity both for powder and annealed sample under the same annealing conditions. Annealing conditions (time and temperature) had large effects on recrystallization behavior of PVC. The crystallinity of PVC decreased with increasing of DOP plasticizer content in PVC compounds, and lead to decrease of modulus and increase of average molecular weight between physical crosslinks.
Blend Morphology of Linear Low Density Polyethylene and Polystyrene in a Non-Intermeshing Twin Screw Extruder
Authors: Yang L.-Y. , Smith T. G. , Bigio D.
Published: December 2013

Morphology development was investigated during blending of linear low density polyethylene (LLDPE) and polystyrene (PS) (the minor phase) in a tangential counter-rotating twin screw extruder, with and without the use of 5 wt.-% Kraton styrene-ethylene/butylene-styrene (SEBS) triblock copolymers as compatibilizing agents. Dispersive mixing in the Non-Intermeshing Twin Screw Extruder (NITSE) is improved with an increase of percent drag flow up to 50 %; the screws configuration includes reverse flight elements and/or cylinders. Experiments have indicated that the combined effect of the reverse flight elements and cylinders increases the reduction rate of droplets due to a longer time in the feed screw where the most significant changes of phase morphology occur. Screw stagger has been shown to have a minor effect on the phase scale of the final dispersion. The more significant reduction of the phase scale is achieved by increasing screw speed under constant flow conditions.
Numerical Analysis of Cooling Air Systems in Film Blowing
Authors: Wolf D. , Feron B. , Wortberg J.
Published: December 2013

Air rings, used today in film blowing systems, have been developed down the years through trial and error experiments. They represent the limiting factor concerning the efficiency of film blowing lines with respect to throughput and take-off speed. Numerical simulation of the cooling process in film blowing provides a tool for the design and optimization of future cooling systems. Individual process and geometric parameters can be changed interactively with the effects on flow and heat transfer processes being analysed and applied to similar situations. The knowledge acquired regarding the physical interactions in the cooling of blown film makes a targeted optimization possible. The purpose of this paper is to present the foundamentals for calculating turbulent air flows in blown film extrusion and, additionally, a model for complete FE-simulation of the flow and heat transfer processes. Furthermore, the achieved simulation results will be discussed.
Effect of Compounding Conditions on Mechanical Properties of Glass Fiber-Reinforced Polyamide-6
Authors: Nagae S. , Nagura K. , Yamagiwa N. , Yamane Y. , Miyake K. , Inoue K.
Published: December 2013

Glass fiber-reinforced polyamide-6 (GFPA-6) was compounded using a HYPERKTX46 twin screw extruder with three different types of screw segments (rotor segments, kneading disc segments and turbine segments). Based on the ‘neural network’ regression analysis, we investigated the effects of compounding conditions, such as screw configurations, screw rotation speed, and production rate on mechanical properties, such as tensile, flexural and impact strength of GFPA-6. It was found that the mechanical properties of GFPA-6 changed in different ways with compounding conditions (screw rotation speed and production rate), depending on the type of screw segments. It was also found that the rotor segment exhibited good mechanical properties in wider ranges of compounding conditions than the kneading disc segment and the turbine segment, probably due to its mild and uniform mixing capability.