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Rangrong Yoksan - One of the best experts on this subject based on the ideXlab platform.
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Effects of pea protein on properties of cassava starch edible Films produced by Blown-Film extrusion for oil packaging
Food Packaging and Shelf Life, 2020Co-Authors: Kedpraveen Huntrakul, Rangrong Yoksan, Amporn Sane, Nathdanai HarnkarnsujaritAbstract:Abstract Starch can be commercially prepared into edible and biodegradable packaging via plasticization and extrusion. However, plasticized starch has poor stability in Blown-Film extrusion processability and storage properties which can be improved by combinations with protein. Edible Films were developed from acetylated cassava starch (AS) and pea protein isolate (PI) using conventional Blown-Film extrusion. Films with PI up to 20 % were determined for physical, thermal and barrier properties and stability for oil packaging. PI stabilized Films during Blown-extrusion but decreased flexibility due to strong inter- and intra-molecular interaction with non-homogeneity of AS-PI blend matrices. Protein dispersed in AS matrices at low PI and formed continuous networks at 20 % which led to increased tensile strength. Increase in PI decreased solubility and light transmission but increased protein aggregation and improved crystallinity, surface hydrophobicity and barrier properties against water vapor and oxygen. Increase in PI also reduced glass transition and relaxation temperatures of AS-PI blends. Heat-sealed AS and AS-PI sachets showed effective protection for soybean and olive oil stored for 3 months at different humidities. PI blending effectively prevented humidity-induced shrinkage of AS Film (up to 55 %) and enhanced polymer-glycerol interaction which improved thermal stability. Blending of starch and plant-derived pea protein effectively improved Blown-Film processability and barrier properties for oil-based food products.
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morphological characteristics and barrier properties of thermoplastic starch chitosan Blown Film
Carbohydrate Polymers, 2016Co-Authors: Khanh Minh Dang, Rangrong YoksanAbstract:Abstract Fabrication of starch-based edible Film using Blown Film extrusion is challenging and interesting because this process provides continuous operation with shorter production time and lower energy consumption, is less labor intensive, and results in higher productivity than the conventional solution casting technique. Previously, we reported on the preparation and some properties of thermoplastic starch/chitosan (TPS/CTS) Blown Films; however, their morphological characteristics and barrier properties had not yet been elucidated. The present work thus aims to investigate the effect of chitosan (0.37–1.45%) on morphological characteristics, water vapor and oxygen barrier properties as well as hydrophilicity of the TPS and TPS/CTS Films. The relationship between morphological characteristics and properties of the Films was also discussed. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS) confirmed the distribution and deposition of chitosan on the Film surface. The existence of chitosan on the surface imparted the improved water vapor and oxygen barrier properties and the reduced surface hydrophilicity to the Film. The results suggest that this biodegradable bio-based TPS/CTS Film could potentially be used as an edible Film for food and pharmaceutical applications.
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Morphological characteristics and barrier properties of thermoplastic starch/chitosan Blown Film
Carbohydrate Polymers, 2016Co-Authors: Khanh Minh Dang, Rangrong YoksanAbstract:Fabrication of starch-based edible Film using Blown Film extrusion is challenging and interesting because this process provides continuous operation with shorter production time and lower energy consumption, is less labor intensive, and results in higher productivity than the conventional solution casting technique. Previously, we reported on the preparation and some properties of thermoplastic starch/chitosan (TPS/CTS) Blown Films; however, their morphological characteristics and barrier properties had not yet been elucidated. The present work thus aims to investigate the effect of chitosan (0.37-1.45%) on morphological characteristics, water vapor and oxygen barrier properties as well as hydrophilicity of the TPS and TPS/CTS Films. The relationship between morphological characteristics and properties of the Films was also discussed. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS) confirmed the distribution and deposition of chitosan on the Film surface. The existence of chitosan on the surface imparted the improved water vapor and oxygen barrier properties and the reduced surface hydrophilicity to the Film. The results suggest that this biodegradable bio-based TPS/CTS Film could potentially be used as an edible Film for food and pharmaceutical applications.
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Development of thermoplastic starch Blown Film by incorporating plasticized chitosan
Carbohydrate Polymers, 2015Co-Authors: Khanh Minh Dang, Rangrong YoksanAbstract:The objective of the present work was to improve Blown Film extrusion processability and properties of thermoplastic starch (TPS) Film by incorporating plasticized chitosan, with a content of 0.37-1.45%. The effects of chitosan on extrusion processability and melt flow ability of TPS, as well as that on appearance, optical properties, thermal properties, viscoelastic properties and tensile properties of the Films were investigated. The possible interactions between chitosan and starch molecules were evaluated by FTIR and XRD techniques. Chitosan and starch molecules could interact via hydrogen bonds, as confirmed from the blue shift of OH bands and the reduction of V-type crystal formation. Although the incorporation of chitosan caused decreased extensibility and melt flow ability, as well as increased yellowness and opacity, the Films possessed better extrusion processability, increased tensile strength, rigidity, thermal stability and UV absorption, as well as reduced water absorption and surface stickiness. The obtained TPS/chitosan-based Films offer real potential application in the food industry, e.g. as edible Films.
Khanh Minh Dang - One of the best experts on this subject based on the ideXlab platform.
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morphological characteristics and barrier properties of thermoplastic starch chitosan Blown Film
Carbohydrate Polymers, 2016Co-Authors: Khanh Minh Dang, Rangrong YoksanAbstract:Abstract Fabrication of starch-based edible Film using Blown Film extrusion is challenging and interesting because this process provides continuous operation with shorter production time and lower energy consumption, is less labor intensive, and results in higher productivity than the conventional solution casting technique. Previously, we reported on the preparation and some properties of thermoplastic starch/chitosan (TPS/CTS) Blown Films; however, their morphological characteristics and barrier properties had not yet been elucidated. The present work thus aims to investigate the effect of chitosan (0.37–1.45%) on morphological characteristics, water vapor and oxygen barrier properties as well as hydrophilicity of the TPS and TPS/CTS Films. The relationship between morphological characteristics and properties of the Films was also discussed. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS) confirmed the distribution and deposition of chitosan on the Film surface. The existence of chitosan on the surface imparted the improved water vapor and oxygen barrier properties and the reduced surface hydrophilicity to the Film. The results suggest that this biodegradable bio-based TPS/CTS Film could potentially be used as an edible Film for food and pharmaceutical applications.
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Morphological characteristics and barrier properties of thermoplastic starch/chitosan Blown Film
Carbohydrate Polymers, 2016Co-Authors: Khanh Minh Dang, Rangrong YoksanAbstract:Fabrication of starch-based edible Film using Blown Film extrusion is challenging and interesting because this process provides continuous operation with shorter production time and lower energy consumption, is less labor intensive, and results in higher productivity than the conventional solution casting technique. Previously, we reported on the preparation and some properties of thermoplastic starch/chitosan (TPS/CTS) Blown Films; however, their morphological characteristics and barrier properties had not yet been elucidated. The present work thus aims to investigate the effect of chitosan (0.37-1.45%) on morphological characteristics, water vapor and oxygen barrier properties as well as hydrophilicity of the TPS and TPS/CTS Films. The relationship between morphological characteristics and properties of the Films was also discussed. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS) confirmed the distribution and deposition of chitosan on the Film surface. The existence of chitosan on the surface imparted the improved water vapor and oxygen barrier properties and the reduced surface hydrophilicity to the Film. The results suggest that this biodegradable bio-based TPS/CTS Film could potentially be used as an edible Film for food and pharmaceutical applications.
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Development of thermoplastic starch Blown Film by incorporating plasticized chitosan
Carbohydrate Polymers, 2015Co-Authors: Khanh Minh Dang, Rangrong YoksanAbstract:The objective of the present work was to improve Blown Film extrusion processability and properties of thermoplastic starch (TPS) Film by incorporating plasticized chitosan, with a content of 0.37-1.45%. The effects of chitosan on extrusion processability and melt flow ability of TPS, as well as that on appearance, optical properties, thermal properties, viscoelastic properties and tensile properties of the Films were investigated. The possible interactions between chitosan and starch molecules were evaluated by FTIR and XRD techniques. Chitosan and starch molecules could interact via hydrogen bonds, as confirmed from the blue shift of OH bands and the reduction of V-type crystal formation. Although the incorporation of chitosan caused decreased extensibility and melt flow ability, as well as increased yellowness and opacity, the Films possessed better extrusion processability, increased tensile strength, rigidity, thermal stability and UV absorption, as well as reduced water absorption and surface stickiness. The obtained TPS/chitosan-based Films offer real potential application in the food industry, e.g. as edible Films.
Richard D. Braatz - One of the best experts on this subject based on the ideXlab platform.
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instabilities and multiplicities in non isothermal Blown Film extrusion including the effects of crystallization
Journal of Process Control, 2011Co-Authors: Carl J Pirkle, Richard D. BraatzAbstract:Abstract Stable operating regions for Blown Film extrusion are mapped using a dynamic model that includes the effect of crystallization on the rheological properties of the polymer. In the computations, the bubble air mass and take-up ratio were held constant, and the machine tension and bubble inflation pressure were treated as dependent variables. For a given bubble air mass, the take-up ratio was used as the continuation parameter for mapping steady-state solutions. The take-up ratio varies smoothly, but not necessarily monotonically, with the machine tension. Curves of either blow-up ratio or thickness reduction versus take-up ratio reveal that there are take-up ratios where no, one, or multiple solutions exist. The heat transfer coefficient from the polymer Film to the external air and surroundings has a marked influence on the qualitative and quantitative features of the blow-up ratio versus thickness reduction curves. Generalized eigenvalue analysis of the linearized Blown Film equations indicates that increasing the heat transfer rate increases the stability of operations. A corresponding decline occurs, however, in the thickness reduction of the Blown Film for a given blow-up ratio.
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a thin shell two phase microstructural model for Blown Film extrusion
Journal of Rheology, 2010Co-Authors: J C Pirkle, Richard D. BraatzAbstract:A two-phase microstructural constitutive relation is combined with the thin-shell model for the simulation of Blown Film extrusion. This combination includes equations for momentum conservation, flow-enhanced crystallization, viscoelasticity, and bubble-tube cooling. Consistent with typical Blown Film operation, the simulations set the bubble air mass and take-up ratio as constants, while treating the machine tension and inflation pressure as dependent variables. In all the simulations performed, the high degree of crystallization, and subsequent system stiffening, located the freeze-line naturally. Bubble geometry, temperature, and crystallinity were fitted to experimental data using material and kinetic parameters mostly obtained by a simpler quasi-cylindrical model. The thin-shell microstructural model was compared to a modified quasi-cylindrical model. The models predict similar responses to operational changes, including axial locked-in stresses at the freeze-line, but have significant differences in the locked-in stresses in the transverse direction, which were attributable to the use of different momentum equations. Either model can be used for data fitting, parameter estimation, and prediction of most process responses to upsets.A two-phase microstructural constitutive relation is combined with the thin-shell model for the simulation of Blown Film extrusion. This combination includes equations for momentum conservation, flow-enhanced crystallization, viscoelasticity, and bubble-tube cooling. Consistent with typical Blown Film operation, the simulations set the bubble air mass and take-up ratio as constants, while treating the machine tension and inflation pressure as dependent variables. In all the simulations performed, the high degree of crystallization, and subsequent system stiffening, located the freeze-line naturally. Bubble geometry, temperature, and crystallinity were fitted to experimental data using material and kinetic parameters mostly obtained by a simpler quasi-cylindrical model. The thin-shell microstructural model was compared to a modified quasi-cylindrical model. The models predict similar responses to operational changes, including axial locked-in stresses at the freeze-line, but have significant differences in...
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Maximum-Likelihood Parameter Estimation for the Thin-Shell Quasi-Newtonian Model for a Laboratory Blown Film Extruder
Industrial & Engineering Chemistry Research, 2010Co-Authors: J C Pirkle, Mitsuko Fujiwara, Richard D. BraatzAbstract:While most plastic Films are manufactured by Blown Film extrusion, their first-principles modeling has remained substantially more challenging than for most other chemical engineering unit operations due to its combination of heat transfer, crystallization, and non-Newtonian fluid mechanics. This paper applies maximum-likelihood parameter estimation to characterize the convective heat transfer characteristics from measured spatial radii and temperature profiles for a laboratory-scale Blown Film process extruding a linear low density polyethylene (LLDPE) polymer. The Pearson and Petrie thin-Film extrusion model incorporates (i) a quasi-Newtonian constitutive relation for the effect of temperature and crystallization on the viscosity of the polymer and (ii) a spatial variation of the heat transfer coefficient that is qualitatively consistent with turbulent flow simulations reported in the literature. A single heat transfer expression fit the experimental conditions for a cooling air flow rate of 1.5 m/s, wh...
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A thin-shell two-phase microstructural model for Blown Film extrusion
Journal of Rheology (1978-present), 2010Co-Authors: J C Pirkle, Richard D. BraatzAbstract:A two-phase microstructural constitutive relation is combined with the thin-shell model for the simulation of Blown Film extrusion. This combination includes equations for momentum conservation, flow-enhanced crystallization, viscoelasticity, and bubble-tube cooling. Consistent with typical Blown Film operation, the simulations set the bubble air mass and take-up ratio as constants, while treating the machine tension and inflation pressure as dependent variables. In all the simulations performed, the high degree of crystallization, and subsequent system stiffening, located the freeze-line naturally. Bubble geometry, temperature, and crystallinity were fitted to experimental data using material and kinetic parameters mostly obtained by a simpler quasi-cylindrical model. The thin-shell microstructural model was compared to a modified quasi-cylindrical model. The models predict similar responses to operational changes, including axial locked-in stresses at the freeze-line, but have significant differences in the locked-in stresses in the transverse direction, which were attributable to the use of different momentum equations. Either model can be used for data fitting, parameter estimation, and prediction of most process responses to upsets. © 2010 The Society of Rheology.
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Comparison of the Dynamic Thin Shell and Quasi-cylindrical Models for Blown Film Extrusion
Polymer Engineering and Science, 2004Co-Authors: J C Pirkle, Richard D. BraatzAbstract:Most models of Blown Film extrusion are based on thin shell theory, which was first applied to these processes by Pearson and Petrie. There has been some contention in the literature as to the suitability of the thin shell model. More recently, Liu and co-workers presented an alternative quasi-cylindrical model that neglects longitudinal curvature but was reported to agree more closely with experiments. In later studies, other researchers used the quasi-cylindrical model to investigate flow-induced crystallization. The current paper presents finite difference solutions of the quasi-cylindrical model and quantifies the differences in the steady-state behavior, dynamics, and stability between the quasi-cylindrical and the thin shell models. The differences in the steady-state and dynamic behavior between the thin shell and quasi-cylindrical models are found to be significant, both qualitatively and quantitatively. This study should aid future researchers in developing dynamic simulation models that include more sophisticated descriptions of the underlying polymer physics. Polym. Eng. Sci. 44:1267–1276, 2004. © 2004 Society of Plastics Engineers.
Amod A. Ogale - One of the best experts on this subject based on the ideXlab platform.
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real time crystalline orientation measurements during low density polyethylene Blown Film extrusion using wide angle x ray diffraction
Polymer Engineering and Science, 2012Co-Authors: G. Gururajan, Amod A. OgaleAbstract:Real-time wide-angle X-ray diffraction studies were successfully used to investigate the effect of Film blowing process parameter on the crystalline orientation development during the Blown Film extrusion of low-density polyethylene. Azimuthal distribution scans showed the evolution of crystalline orientation in the bubble from an isotropic state to an oriented state as inferred from (110) and (200) planes. These real-time X-ray diffraction measurements in a Blown Film line are consistent with prior observations using polarized Raman spectroscopy (Gururajan and Ogale, J. Raman Spectrosc., 40, 212 (2009)) and small-angle light scattering (Bullwinkel et al., Int. Polym. Proc., 16, 41 (2001)) that significant molecular orientation takes place past the frost-line height, even after the Blown Film diameter is locked into place. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
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Real‐time crystalline orientation measurements during low‐density polyethylene Blown Film extrusion using wide‐angle X‐ray diffraction
Polymer Engineering and Science, 2012Co-Authors: G. Gururajan, Amod A. OgaleAbstract:Real-time wide-angle X-ray diffraction studies were successfully used to investigate the effect of Film blowing process parameter on the crystalline orientation development during the Blown Film extrusion of low-density polyethylene. Azimuthal distribution scans showed the evolution of crystalline orientation in the bubble from an isotropic state to an oriented state as inferred from (110) and (200) planes. These real-time X-ray diffraction measurements in a Blown Film line are consistent with prior observations using polarized Raman spectroscopy (Gururajan and Ogale, J. Raman Spectrosc., 40, 212 (2009)) and small-angle light scattering (Bullwinkel et al., Int. Polym. Proc., 16, 41 (2001)) that significant molecular orientation takes place past the frost-line height, even after the Blown Film diameter is locked into place. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
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Molecular orientation evolution during low‐density polyethylene Blown Film extrusion using real‐time Raman spectroscopy
Journal of Raman Spectroscopy, 2008Co-Authors: G. Gururajan, Amod A. OgaleAbstract:Real-time polarized Raman spectroscopy was used in this study to measure the molecular orientation evolution during Blown Film extrusion of low-density polyethylene (LDPE). Spectra were obtained at different locations along the Blown Film line, starting from the molten state near the die and extending up to the solidified state near the nip rolls. The trans CC symmetrical stretching vibration of polyethylene (PE) at 1132 cm−1 was analyzed for Films possessing uniaxial symmetry. For the given peak, the principal axis of the Raman tensor is coincident with the c-axis of the orthorhombic crystal, and was used to solve a set of intensity ratio equations to obtain second (〈P2(cosθ)〉) and fourth (〈P4(cosθ)〉) moments of the orientation distribution function. The orientation parameters (P2, P4) were found to increase along the axial distance in the Film line even past the frost-line height (FLH). The P2 values also showed an increasing trend with crystalline evolution during extrusion, consistent with past observations that molecular orientation takes place even after the Blown Film diameter is locked into place. It was also found that the integral ratio (I1132/I1064) obtained from a single, ZZ-back-scattered mode can provide a reasonable estimate of molecular orientation. These results indicate the potential of real-time Raman spectroscopy as a rapid microstructure monitoring tool for better process control during Blown Film extrusion. Copyright © 2008 John Wiley & Sons, Ltd.
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Real-time wide-angle X-ray diffraction during polyethylene Blown Film extrusion
Polymer Engineering and Science, 2008Co-Authors: G. Gururajan, H. Shan, G. Lickfield, Amod A. OgaleAbstract:Real-time wide-angle X-ray diffraction (WAXD) measurements during Blown Film extrusion of low-density polyethylene are reported in this study. WAXD patterns were obtained at different axial positions in the Blown Film line starting from a location near the die and extending up to the nip-roller. The X-ray diffraction patterns from the bubble were analyzed for crystalline growth along the bubble. From the evolution of (110) and (200) peaks, it is evident that the crystallization process starts near the frost-line height (FLH), shows a steep growth immediately past the FLH, and then plateaus at higher axial distances near the nip-rolls. The real-time crystallinity profiles obtained from WAXD were consistent with those measured using real-time Raman spectroscopy. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
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Real-time Raman spectroscopy during LDPE/PP bilayer Blown-Film extrusion
Plastics Rubber and Composites, 2005Co-Authors: G. Gururajan, Amod A. OgaleAbstract:AbstractThe present study reports on a technique for real-time Raman spectroscopic measurement of crystallinity of the individual components of a bicomponent Film (LDPE/PP) during Blown-Film extrusion. The 1296–1305 cm−1 band, observed predominantly for PE, was slightly masked by the contribution from the PP layer. However, the 809–841 cm−1 band was unique for PP and unaffected by the presence of the PE layer. Thus, Raman spectra for PE/PP bilayer Films consist of superimposed spectra of the components with some overlapping peaks but some distinct peaks. These distinct peaks enable successful real-time crystallinity measurement during coextrusion of LDPE/PP Films.
J C Pirkle - One of the best experts on this subject based on the ideXlab platform.
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a thin shell two phase microstructural model for Blown Film extrusion
Journal of Rheology, 2010Co-Authors: J C Pirkle, Richard D. BraatzAbstract:A two-phase microstructural constitutive relation is combined with the thin-shell model for the simulation of Blown Film extrusion. This combination includes equations for momentum conservation, flow-enhanced crystallization, viscoelasticity, and bubble-tube cooling. Consistent with typical Blown Film operation, the simulations set the bubble air mass and take-up ratio as constants, while treating the machine tension and inflation pressure as dependent variables. In all the simulations performed, the high degree of crystallization, and subsequent system stiffening, located the freeze-line naturally. Bubble geometry, temperature, and crystallinity were fitted to experimental data using material and kinetic parameters mostly obtained by a simpler quasi-cylindrical model. The thin-shell microstructural model was compared to a modified quasi-cylindrical model. The models predict similar responses to operational changes, including axial locked-in stresses at the freeze-line, but have significant differences in the locked-in stresses in the transverse direction, which were attributable to the use of different momentum equations. Either model can be used for data fitting, parameter estimation, and prediction of most process responses to upsets.A two-phase microstructural constitutive relation is combined with the thin-shell model for the simulation of Blown Film extrusion. This combination includes equations for momentum conservation, flow-enhanced crystallization, viscoelasticity, and bubble-tube cooling. Consistent with typical Blown Film operation, the simulations set the bubble air mass and take-up ratio as constants, while treating the machine tension and inflation pressure as dependent variables. In all the simulations performed, the high degree of crystallization, and subsequent system stiffening, located the freeze-line naturally. Bubble geometry, temperature, and crystallinity were fitted to experimental data using material and kinetic parameters mostly obtained by a simpler quasi-cylindrical model. The thin-shell microstructural model was compared to a modified quasi-cylindrical model. The models predict similar responses to operational changes, including axial locked-in stresses at the freeze-line, but have significant differences in...
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Maximum-Likelihood Parameter Estimation for the Thin-Shell Quasi-Newtonian Model for a Laboratory Blown Film Extruder
Industrial & Engineering Chemistry Research, 2010Co-Authors: J C Pirkle, Mitsuko Fujiwara, Richard D. BraatzAbstract:While most plastic Films are manufactured by Blown Film extrusion, their first-principles modeling has remained substantially more challenging than for most other chemical engineering unit operations due to its combination of heat transfer, crystallization, and non-Newtonian fluid mechanics. This paper applies maximum-likelihood parameter estimation to characterize the convective heat transfer characteristics from measured spatial radii and temperature profiles for a laboratory-scale Blown Film process extruding a linear low density polyethylene (LLDPE) polymer. The Pearson and Petrie thin-Film extrusion model incorporates (i) a quasi-Newtonian constitutive relation for the effect of temperature and crystallization on the viscosity of the polymer and (ii) a spatial variation of the heat transfer coefficient that is qualitatively consistent with turbulent flow simulations reported in the literature. A single heat transfer expression fit the experimental conditions for a cooling air flow rate of 1.5 m/s, wh...
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A thin-shell two-phase microstructural model for Blown Film extrusion
Journal of Rheology (1978-present), 2010Co-Authors: J C Pirkle, Richard D. BraatzAbstract:A two-phase microstructural constitutive relation is combined with the thin-shell model for the simulation of Blown Film extrusion. This combination includes equations for momentum conservation, flow-enhanced crystallization, viscoelasticity, and bubble-tube cooling. Consistent with typical Blown Film operation, the simulations set the bubble air mass and take-up ratio as constants, while treating the machine tension and inflation pressure as dependent variables. In all the simulations performed, the high degree of crystallization, and subsequent system stiffening, located the freeze-line naturally. Bubble geometry, temperature, and crystallinity were fitted to experimental data using material and kinetic parameters mostly obtained by a simpler quasi-cylindrical model. The thin-shell microstructural model was compared to a modified quasi-cylindrical model. The models predict similar responses to operational changes, including axial locked-in stresses at the freeze-line, but have significant differences in the locked-in stresses in the transverse direction, which were attributable to the use of different momentum equations. Either model can be used for data fitting, parameter estimation, and prediction of most process responses to upsets. © 2010 The Society of Rheology.
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Comparison of the Dynamic Thin Shell and Quasi-cylindrical Models for Blown Film Extrusion
Polymer Engineering and Science, 2004Co-Authors: J C Pirkle, Richard D. BraatzAbstract:Most models of Blown Film extrusion are based on thin shell theory, which was first applied to these processes by Pearson and Petrie. There has been some contention in the literature as to the suitability of the thin shell model. More recently, Liu and co-workers presented an alternative quasi-cylindrical model that neglects longitudinal curvature but was reported to agree more closely with experiments. In later studies, other researchers used the quasi-cylindrical model to investigate flow-induced crystallization. The current paper presents finite difference solutions of the quasi-cylindrical model and quantifies the differences in the steady-state behavior, dynamics, and stability between the quasi-cylindrical and the thin shell models. The differences in the steady-state and dynamic behavior between the thin shell and quasi-cylindrical models are found to be significant, both qualitatively and quantitatively. This study should aid future researchers in developing dynamic simulation models that include more sophisticated descriptions of the underlying polymer physics. Polym. Eng. Sci. 44:1267–1276, 2004. © 2004 Society of Plastics Engineers.
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Dynamic modeling of Blown‐Film extrusion
Polymer Engineering and Science, 2003Co-Authors: J C Pirkle, Richard D. BraatzAbstract:Past dynamic studies of Blown-Film extrusion have been confined to the stability analysis of the linearized equations. The full set of nonlinear equations comprises a system of partial differential and algebraic equations with boundary conditions that vary from author to author. In this paper, the Numerical-Method-of-Lines, which combines finite-difference methods with ordinary differential/algebraic equation integrators, is used to solve the full system. Appropriate boundary conditions are selected to give physical results that compare well with experiment. An important boundary condition is the “minimum order reduction” condition on the gradient of the bubble-tube radius with respect to distance above the extrusion die (the axial position). Transient startups and operational disturbances are examined. Calculations show the influence of oscillations in operating conditions such as heat transfer or inflation pressure on the bubble-tube radius and Film thickness. Steady-state results obtained by integrating the transient equations for a sufficiently long time are qualitatively in agreement with experiment, in contrast to past simulations of these equations.
