Blown Film Extrusion Process for Polybags: Technical Overview and Applications

The choice of extrusion process is a decisive factor that affects the finished product quality for polybag manufacturing. One important component influencing the quality of the finished product is the selection of the extrusion technique. Two popular procedures that vary in the kind of dye used and the final product’s texture are cast film and blown film. In the horizontal extrusion moulding method known as “cast film”, heated resin is injected into a flat dye and allowed to cool on chill rolls. The film produced is clear, lightweight, and appropriate for lamination;its thickness varies based on the winding speed and the film is slower to crystallize and has less clarity but more durability because the resin molecules have reoriented, facing limitation of high wastage generation. This study primarily focused on the preparation of polybag film using the blown film extrusion process, utilizing high-quality polymer resins such as polyester polyethylene (PP) and linear low-density polyethylene (LLDPE) to minimize waste generation. The novelty of the process was reflected in minimising the waste generation. The control parameters considered in this study are temperature, pressure, and air intake volume. We investigated the influence of these critical process control parameters on the gauge thickness, optical properties, and mechanical strength of the polybag film produced through blown film extrusion. Additionally, we replicated the blown film process using simulation software developed at Pennsylvania College of Technology. The simulation results confirmed the overall stability of the polybag film produced through the blown film extrusion process.

Effects of correlative factors on the interdendritic melt flow brought by the bulge in continuous casting slabs

The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.

Semi-continuous casting of magnesium alloy AZ91 using a filtered melt delivery system

A 3-D numerical simulation of an industrial-sized slab caster for magnesium alloy AZ91 has been carried out for the steady state operational phase of the caster.The simulated model consists of an open-top melt delivery system fitted with a porous filter near the hot-top.The melt flow through the porous filter was modeled on the basis of Brinkmann-Forchimier-Extended non-Darcy model for turbulent flow.An in-house 3-D CFD code was modified to account for the melt flow through the porous filter.Results are obtained for four casting speeds namely,40,60,80,and 100 mm/min.The metal-mold contact region as well as the convective heat transfer coefficient at the mold wall were also varied.In addition to the above,the Darcy number for the porous media was also changed.All parametric studies were performed for a fixed inlet melt superheat of 64℃.The results are presented pictorially in the form of temperature and velocity fields.The sump depth,mushy region thickness,solid shell thickness at the exit of the mold and axial temperature profiles are also presented and correlated with the casting speed through regression analysis.©2015 Production and hosting by Elsevier B.V.on behalf of Chongqing University.

Effect of electromagnetic parameters on melt flow and heat transfer of AZ80 Mg alloy during differential phase electromagnetic DC casting based on numerical simulation

Based on multi-physical field coupling numerical simulation method,magnetic field distribution,melt flow,and heat transfer behavior of aΦ300 mm AZ80 alloy billet during differential phase electromagnetic DC casting(DP-EMC)with different electromagnetic parameters were studied.The results demonstrate that the increase in current intensity only changes the magnitude but does not change the Lorentz force's distribution characteristics.The maximum value of the Lorentz force increases linearly followed by an increase in current intensity.As the frequency increases,the Lorentz force's r component remains constant,and the z component decreases slightly.The change in current intensity correlates with the melt oscillation and convection intensity positively,as well as the liquid sump temperature uniformity.It does not mean that the higher the electric current,the better the metallurgical quality of the billet.A lower frequency is beneficial to generate a more significant melt flow and velocity fluctuation,which is helpful to create a more uniform temperature field.Appropriate DP-EMC parameters for aΦ300 mm AZ80 Mg alloy are 10-20 Hz frequency and 80-100 A current intensity.

Melt flow,heat transfer and solidification in a flexible thin slab continuous casting mold with vertical-combined electromagnetic braking

During continuous casting of steel slabs,the application of electromagnetic braking technology(EMBr)provides an effective tool to influence solidification by controlling the pattern of melt flow in the mold.Thus,the quality of the final product can be improved considerably.A new electromagnetic braking(EMBr)method,named vertical-combined electromagnetic braking(VC-EMBr),is proposed to be applied to a flexible thin slab casting(FTSC)mold.To evaluate the beneficial effects of the VC-EMBr,the melt flow,heat transfer,and solidification processes in the FTSC mold are studied by means of numerical simulations.In detail,a Reynolds-averaged Navier–Stokes turbulence model together with an enthalpy-porosity approach was used.The numerical findings are compared with respective simulations using the traditional Ruler-EMBr.The results demonstrate that the application of the VC-EMBr contributes significantly to preventing relative slab defects.In contrast to the Ruler-EMBr,the additional vertical magnetic poles of the VC-EMBr preferentially suppress the direct impact of jet flow on the narrow face of FSTC mold and considerably diminish the level fluctuation near the meniscus region.For instance,by applying a magnetic flux density of 0.3 T,the maximum amplitude of meniscus deflection reduces by about 80%.Moreover,the braking effect of the VC-EMBr effectively improves the homogeneity of temperature distribution in the upper recirculation region and increases the solidified shell thickness along the casting direction.On this basis,the newly proposed VC-EMBr shows a beneficial effect in preventing relative slab defects for FTSC thin slab continuous casting.

Numerical simulation of flow characteristics in settler of flash furnace

A computational fluid dynamics （CFD） simulation was carried out with CFX4,3 to investigate the melt flow and temperature distributions in the settler of a flash furnace. Sixteen cases of one slag tap hole adopted with one matte tap hole （1-to-l） and one slag tap hole adopted with two matte tap holes （1-to-2） operation modes were modelled. The simulation results show that the melt flows are similar in both two operation modes, but evident circulations can be found in the case of the 1-to-2 operation mode. The combination modes of the slag and matte tap holes are found to have a significant effect on the temperature distributions of the melt. The melt temperature is more uniform in the case of the 1-to-2 mode. Selection of a matte tap hole farther away from the inlet is more conducive to achieve a uniform distribution of the melt temperature in the settler in nractical tannine oneration

Simulation of the continuous casting process in a mold of free-cutting steel 38MnVS based on a MiLE method

A new method called mixed Lagrangian and Eulerian （MiLE） method was used to simulate the continuous casting process in a mold of free-cutting steel 38MnVS.The simulation results are basically in agreement with experimental data in the literature,achieving the three-dimensional visualization of temperature distribution,melt flow,shell thickness,and stress distribution of blooms in a mold.It is shown that the flow velocity of steel melt becomes smaller gradually as the casting proceeds.When the flow reaches a certain depth,two types of flow patterns can be observed in the upper zone of the mold.The first flow pattern is to flow downwards,and the second one is to flow upwards to the meniscus.The corner temperature is higher,and the thickness is thinner than those in the mid-face.The effective stress in the corner area is much bigger than that in the mid-face,indicating that the corner area is the dangerous zone of cracking.

On numerical modeling of low-head direct chill ingot caster for magnesium alloy AZ31

A comprehensive 3D turbulent CFD study has been carried out to simulate a Low-Head(LH)vertical Direct Chill(DC)rolling ingot caster for the common magnesium alloy AZ31.The model used in this study takes into account the coupled laminar/turbulent melt flow and solidification aspects of the process and is based on the control-volume finite-difference approach.Following the aluminum/magnesium DC casting industrial practices,the LH mold is taken as 30 mm with a hot top of 60 mm.The previously verified in-house code has been modified to model the present casting process.Important quantitative results are obtained for four casting speeds,for three inlet melt pouring temperatures(superheats)and for three metal-mold contact heat transfer coefficients for the steady state operational phase of the caster.The variable cooling water temperatures reported by the industry are considered for the primary and secondary cooling zones during the simulations.Specifically,the temperature and velocity fields,sump depth and sump profiles,mushy region thickness,solid shell thickness at the exit of the mold and axial temperature profiles at the center and at three strategic locations at the surface of the slab are presented and discussed.

INFLUENCE OF EXTERNAL MAGNETIC FIELD ON THE FLOW FIELD IN MOLTEN SEMICONDUCTOR OF CZOCHRALSKI CRYSTAL GROWTH——A NUMERICAL SIMULATION

Numerical results show that an external magnetic field may influence significantly the flow pattern in the molten semiconductor of Czochralski crystal growth. The melt flow could be pronouncedly damped by a magnet. ic field with the intensity of several thousands Gauss, while the temperature field is affected only in a less extent by the magnetic field.

Rheological,mechanical,thermal,tribological and morphological properties of PLA-PEKK-HAp-CS composite

The present study reports investigations on rheological,mechanical,thermal,tribological and morphological properties of feedstock filaments prepared with polylactic acid-polyether ketone ketone-hydroxyapatite-chitosan(PLA-PEKK-HAp-CS)composite for 3D printing of functional prototypes.The study consists of a series of melt processing operations on melt flow index(MFI)setup as per ASTM D-1238 for melt flow certainty followed by fixation of reinforcement composition/proportion as 94%PEKK-4%HAp-2%CS(B)by mass in PLA matrix(A).The blending of reinforcement and preparation of feedstock filament for fused deposition modeling(FDM)set up has been performed on commercial twin screw extruder(TSE).The results of study suggest that feedstock filaments prepared with blend of 95%A-5%B(by mass)at 200℃processing temperature and 100 r/min rotational speed on TSE resulted into better tensile properties(35.9 MPa peak strength and 32.3 MPa break strength)with 6.24%surface porosity,42.67 nm surface roughness(R_(a))and acceptable heat capacity(2.14 J/g).However as regards to tribological behavior,the minimum wear of 316μm was observed for sample with poor tensile properties.As regards to crash application for scaffolds the maximum toughness of 1.16 MPa was observed for 85%A-15%B(by mass)at 200℃processing temperature and 150 r/min rotational speed on TSE.

Melt flow,solidification structures,and defects in 316 L steel strips produced by vertical centrifugal casting

Vertical centrifugal casting can significantly enhance the filling capability of molten metals,enabling the production of complex thin-walled castings at near-rapid cooling rates.In this study,the melt flow,solidification structures,and defects in 316 L steel cast strips with a geometry of 80 mm×60 mm×2.5 mm produced by vertical centrifugal casting were numerically and experimentally analyzed under different rotation speeds.With gradually increasing the rotation speed from 150 r/min to 900 r/min,the simulated results showed the shortest filling time and minimum porosity volume in the cast strip at a rotation speed of 600 r/min.Since a strong turbulent flow was generated by the rotation of the mold cavity during the filling process,experimental results showed that a“non-dendritic”structure was obtained in 316 L cast strip when centrifugal force was involved,whereas the typical dendritic structure was observed in the reference sample without rotation.Most areas of the cast strip exhibited one-dimensional cooling,but three-sided cooling appeared near the side of the cast strip.Moreover,the pores and cracks in the 316 L strips were detected by computed tomography scanning and analyzed with the corresponding numerical simulations.Results indicated the existence of an optimal rotational speed for producing cast strips with minimal casting defects.This study provides a better understanding of the filling and solidification processes of strips produced by vertical centrifugal casting.

Microstructures,Deformation Mechanisms and Seismic Properties of Synkinematic Migmatite from Southeastern Tibet:Insights from the Migmatitic Core of the Ailao Shan-Red River Shear Zone,Western Yunnan,China

Seismic anisotropy originating within the continental crust is commonly used to determine the deformation and kinematic flow within active orogens and is attributed to regionally oriented mica or hornblende grains.However,naturally deformed rocks usually contain compositional layers(e.g.,parallel compositional banding).It is necessary to understand how both varying mineral contents and differing intensities of compositional layering influence the seismic properties of the deep crust.In this study,we analyzed the seismic response of migmatitic amphibolite with compositional banding structures.We present the microstructures,fabrics,calculated seismic velocities,and seismic anisotropies of mylonitic amphibolite from a horizontal shear layer preserved within the Ailao Shan-Red River shear zone,southwestern Yunnan,China.The investigated sample is characterized by pronounced centimeter-scale compositional banding.The microstructures and fabrics suggest that migmatitic amphibolite rocks within deep crust may delineate regions of deformation-assisted,channelized,reactive,porous melt flow.The origin of compositional banding in the studied migmatitic amphibolite is attributed primarily to partial melting together with some horizontal shearing deformation.The microfabrics and structures investigated in this study are considered to be typical for the base of active horizontal shear layers in the deep crust of southeastern Tibet.Seismic responses are modeled by using crystal preferred orientations for minerals of the migmatitic amphibolite by applying the Voigt-Reuss-Hill homogenization method.Calculated P-wave and S-wave velocities are largely consistent in the various layers of the migmatite.However,seismic anisotropies of P-wave(AV_(p))and S-wave(AVs)are higher in the melanosomes(AV_(p)=5.6%,AV_(s)=6.83%)than those in the leucosomes and the whole rock(AV_(p)=4.2%–4.6%,AV_(s)=3.1%–3.2%).In addition,there is pronounced,S-wave splitting oblique to the foliation plane in the migmatitic amphibolite.The multiple parallel compositional layers generate marked variation in the geometry of the seismic anisotropy(Vs1 polarization)in the whole rock.Combined with the macroscale geographical orientation of fabrics in the Ailao Shan-Red River shear zone,these compositional banding effects are inferred to generate significant variations in the magnitude and orientation of seismic anisotropy,especially for shear-wave anisotropy(AV_(s))in the deep crust.Hence,our data suggest that layering of various origins(e.g.,shear layers,partial-melting layers,and compositional layers)represents a new potential source of anisotropy within the deep crust.

Experiment and numerical simulation of melt convection and oxygen distribution in 400-mm Czochralski silicon crystal growth

Single-crystalline silicon materials with large dimensions have been widely used as assemblies in plasma silicon etching machines.However,information about large-diameter low-cost preparation technology has not been sufficiently reported.In this paper,it was focused on the preparation of 400-mm silicon（100） crystal lightly doped with boron from 28-in.hot zones.Resistivity uniformity and oxygen concentration of the silicon crystal were investigated by direct-current（DC） four-point probes method and Fourier transform infrared spectroscopy（FTIR）,respectively.The global heat transfer,melt flow and oxygen distribution were calculated by finite element method（FEM）.The results show that 28-in.hot zones can replace conventional 32 in.ones to grow 400-mm-diameter silicon single crystals.The change in crucible diameter can save energy,reduce cost and improve efficiency.The trend of oxygen distribution obtained in calculations is in good agreement with experimental values.The present model can well predict the 400-mm-diameter silicon crystal growth and is essential for the optimization of furnace design and process condition.

A Study of Melt Flow Analysis of an ABS-Iron Composite in Fused Deposition Modelling Process

Fused deposition modelling (FDM) is a filament based rapid prototyping system which offers the possibility of introducing new composite material for the FDM process as long as the new material can be made in feedstock filament form. Swinburne has been undertaking extensive research in development of new composite materials involving acrylonitrile-butadiene-styrene (ABS) and other materials including metals. In order to predict the behaviour of new ABS based composite materials in the course of FDM process, it is necessary to investigate the flow of the composite material in liquefier head. No such study is available considering the geometry of the liquefier head. This paper presents 2-D and 3-D numerical analysis of melt flow behaviour of a representative ABS-iron composite through the 90-degree bent tube of the liquefier head of the fused deposition modelling process using ANSYS FLOTRAN and CFX finite element packages. Main flow parameters including temperature, velocity, and pressure drop have been investigated. Filaments of the filled ABS have been fabricated and characterized to verify the possibility of prototyping using the new material on the current FDM machine. Results provide promising information in developing the melt flow modelling of metal-plastic composites and in optimising the FDM parameters for better part quality with such composites.

Melt Rheology of Poly(Lactic Acid) Plasticized by Epoxidized Soybean Oil

This study investigated that epoxidized soybean oil （ESO） was blended as plasticizer with poly （lactic acid） （PLA） and its effects on the melt rheological properties, such as melt flow index, apparent shear viscosity, and melt strength of the blends. PLA was blended by the twin-screw plastic extruder at five mass fractions： 3%, 6%, 9%, 12%, and 15% （based on PLA mass）. Melt flow index （MFI） was examined with a melt flow indexer. The results indicate that the blends of PLA/ESO had higher MFI than pure PLA, except for MFI at 9% reaching to the lowest point, even lower than that of pure PLA. Melt rheological properties were studied by a capillary rheometer in a temperature range of 160-180℃. The blends exhibited shear-thinning behavior and the apparent shear viscosity was well described by the power law in this shear rate region. The melt strength of PLA plasticized with 6% ESO reached the maximums. ESO was more effective in increasing the melt strength at the mass fractions less than 6%, which could toughen the blends to some extent. Therefore, the authors suggested the optimum addition level of 6%-9% ESO will get good melt rheological performance balance.

Simulation of 3D Heat and Mass Transfer in Glass and Oxide Melts Using the Inductive Skull Melting Technology

The inductive skull melting technology has many advantages for melting of innovative materials in the field of glasses and oxides.It offers high processing temperatures and the compliance of necessary purities at the same time. Applicable materials are in particular optical glasses,which are applied for lenses,fibers or filters,because the skull melting technology allows high process temperatures and high purities of the final product.In the production of glass materials strong requirements have to be fulfilled regarding the optical characteristics,which are mainly defined and influenced by the melting of the raw material and the following refining process.An unsolved problem in the melting process of glasses and oxides using the inductive skull melting technology was in the past the unknown heat and mass transfer in the melt because temperature and melt flow measurements in the melt are practically impossible due to the high temperatures.On the other hand the temperature and velocity distribution in the melt is very important regarding the safety of the melting process,the process control for producing the required properties of the material or the further development of skull melting installations.The paper describes a new numerical model which is able to simulate the instationary 3D melt flow of glasses and oxides.The numerical model takes into account electromagnetic,convection and Marangoni forces.By this a comprehensive view of the hidden processes in the practical experiments could be obtained. By means of the new numerical model different glass and oxide melting processes were simulated and the results were compared with experimental results.The comparisons show first of all a very good agreement between experimental and numerical results at the melt surfaces.Additionally the numerical results allow to look much deeper inside the melt and show interesting new effects of the heat and mass transfer below the melt surface which were unknown before.

Architecting Branch Structure in Terpolymer of CO_(2),Propylene Oxide and Phthalic Anhydride:An Enhancement in Thermal and Mechanical Performances

Poly(propylene carbonate phthalate)(PPC-P)is a chemically modified poly(propylene carbonate)(PPC)biodegradable thermoplastic by introducing phthalic anhydride(PA)as the third monomer into the copolymerization of propylene oxide(PO)and CO_(2).To enhance the thermal and mechanical properties of PPC-P,a branching agent pyromellitic anhydride(PMDA)was introduced into the terpolymerization of PO,PA and CO_(2).The resulting copolymers with branched structure,named branched PPC-P,can be obtained using metal-free Lewis pair consisting of triethyl borane(TEB)and bis(triphenylphosphine)iminium chloride(PPNCl)as catalyst.The products obtained were analyzed by NMR spectroscopy and their thermal,mechanical properties and melt processability were evaluated by DSC,TGA,tensile test and melt flow index(MFI)measurement.The obtained branched PPC-P has a high molecular weight up to 156.0 kg·mol^(-1).It shows an increased glass transition temperature(Tg)higher than 50℃and an enhanced tensile strength as high as 38.9 MPa.Noteworthily,the MFI value decreases obviously,indicative of an improved melt strength arising from the branched structure and high molecular weight.What is more,the branched PPC-P exhibits reasonable biodegradability,which demonstrates the great potential as a new green thermoplastic for the family of biodegradable plastics.

Effect of transverse static magnetic field on radial microstructure of hypereutectic aluminum alloy during directional solidification

The effect of different scales thermoelectric magnetic convection(TEMC)on the radial solidification microstructure of hypereutectic Al alloy has been investigated under transverse static magnetic field during directional solidification,focusing on the formation of freckle.Our experimental and numerical simulation results indicate that the TEMC circulation at sample scale under transverse static magnetic field leads to the enrichment of solute Al on one side of the sample.The TEMC and the solute enrichment degree increase with the increase of magnetic field when the magnetic field increases to 0.5 T.The enrichment degree of solute elements under magnetic field is affected by temperature gradient and growth rate.The non-uniform distribution of solute Al in the radial direction of the sample results in the non-uniform distribution of primary dendrite arm spacing(PDAS).Moreover,the applied magnetic field can lead to freckle formation and its number increases with the increase of magnetic field.The change of freckle is consistent with the anisotropy TEMC caused by the anisotropy of primary dendrite or primary dendrite network under magnetic field.Finally,the mechanism of synergism effect of the anisotropy TEMC,the distribution of solute Al and the PDAS on freckle formation and evolution is studied during directional solidification under magnetic field.

Three-dimensional numerical simulation for plastic injection-compression molding

Compared with conventional injection mold- ing, injection-compression molding can mold optical parts with higher precision and lower flow residual stress. However, the melt flow process in a closed cavity becomes more complex because of the moving cavity boundary during compression and the nonlinear problems caused by non-Newtonian polymer melt. In this study, a 3D simulation method was developed for injection-compres- sion molding. In this method, arbitrary Lagrangian- Eulerian was introduced to model the moving-boundary flow problem in the compression stage. The non-New- tonian characteristics and compressibility of the polymer melt were considered. The melt flow and pressure distribution in the cavity were investigated by using the proposed simulation method and compared with those of injection molding. Results reveal that the fountain flow effect becomes significant when the cavity thickness increases during compression. The back flow also plays an important role in the flow pattem and redistribution of cavity pressure. The discrepancy in pressures at different points along the flow path is complicated rather than monotonically decreased in injection molding.

Development of a Non-Contact Electromagnetic Surface Velocity Sensor for Molten Metal Flow

During continuous casting of steel,knowledge of both direction and magnitude of the velocity at the mold surface is of special interest.However,the surface is covered by a non-transparent layer of mold powder to prevent formation of slag.Thus,this meniscus flow cannot be registered by optical measurement techniques.Non-contact measurement methods are of interest.One of such non-invasive techniques is Lorentz force veloeimetry(LFV).It is based on measuring the electromagnetically induced force acting on a magnet system.In this paper we present a series of experiments that aim to demonstrate the feasibility of using two identical velocimeters,termed Time-of-Flight LFV(ToF LFV).Using ToF LFV the free-surface velocity may be purely determined by cross-correlating the two force signals delivered by the two force sensors.We have developed a special prototype of such a measuring device termed meniscus velocity sensor(MVS).It has been designed to record local surface velocities in high-temperature metal melts.At Ilmenau University of Technology,the method has been successfully tested using both solid body movement and Ga^(68%)In^(20%)Sn^(12%)as a low-melting model melt.In the present paper we apply this technique to the case of high-temperature metal melts.In more detail,we present test measurements under industry-relevant conditions using both Sn^(32%)pb^(52%)Bi at 210℃ and molten steel at about 1700℃.These experiments were conducted at Key Laboratories on EPM at North Eastern University.The evaluation of the data shows that our prototype of MVS works well in producing reproducible signals of which surface velocity can be determined.