The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Richard D. Braatz - One of the best experts on this subject based on the ideXlab platform.

  • instabilities and multiplicities in non isothermal blown Film Extrusion including the effects of crystallization
    Journal of Process Control, 2011
    Co-Authors: Carl J Pirkle, Richard D. Braatz
    Abstract:

    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.

  • a thin shell two phase microstructural model for blown Film Extrusion
    Journal of Rheology, 2010
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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...

  • Maximum-Likelihood Parameter Estimation for the Thin-Shell Quasi-Newtonian Model for a Laboratory Blown Film Extruder
    Industrial & Engineering Chemistry Research, 2010
    Co-Authors: J C Pirkle, Mitsuko Fujiwara, Richard D. Braatz
    Abstract:

    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...

  • A thin-shell two-phase microstructural model for blown Film Extrusion
    Journal of Rheology (1978-present), 2010
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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.

  • Comparison of the Dynamic Thin Shell and Quasi-cylindrical Models for Blown Film Extrusion
    Polymer Engineering and Science, 2004
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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.

Garth L Wilkes - One of the best experts on this subject based on the ideXlab platform.

  • a tubular Film Extrusion of poly vinylidene fluoride structure process property behavior as a function of molecular weight
    Polymer, 2004
    Co-Authors: Jiannong Xu, Matthew B Johnson, Garth L Wilkes
    Abstract:

    Abstract Five different poly(vinylidene fluoride) (PVDF) resins spanning the molecular weights from 85,000–250,000 g/mol with nearly comparable polydispersities of ca. 2.0 were investigated with respect to their strain induced crystalline morphologies as produced by a tubular uniaxial Film Extrusion process. By holding the process time window constant through the use of fixed melt temperature, line speed, quench height and Film thickness, it was noted that as molecular weight increased, the uniaxial Films produced systematically change from nearly a spherulitic structure to that of an extremely high concentration of fibril nuclei with minimal growth of folded chain lamella developing perpendicular to the fibrils. The systematic variation in the morphology was directly coupled through consideration of the melt process time window in conjunction with the characteristic relaxation time of a given resin at a given temperature. The latter was determined through use of a Carreau–Yasuda analysis of the melt rheological behavior of each resin and this relaxation time, when correlated to the process time, produced a relative Deborah number. It was distinctly shown that when the Deborah number was considerably less than unity, little crystal orientation was observed in the morphological texture whereas in the range of unity, a distinct rise in crystalline orientation occurred leading to fibril nucleation with lamella side growth in the form of the well known row structure morphology. Exceeding a Deborah number of unity led to nearly full crystalline orientation saturation and to a very high concentration of fibril nucleai with relatively few orthogonal lamella observable. The morphological textures were investigated using AFM, WAXS, SALS, SAXS and birefringence. Use of thermal analysis to determine some of the polymorphic character of the PVDF crystal form was also undertaken.

  • A tubular Film Extrusion of poly(vinylidene fluoride): structure/process/property behavior as a function of molecular weight
    Polymer, 2004
    Co-Authors: Jiannong Xu, Matthew B Johnson, Garth L Wilkes
    Abstract:

    Abstract Five different poly(vinylidene fluoride) (PVDF) resins spanning the molecular weights from 85,000–250,000 g/mol with nearly comparable polydispersities of ca. 2.0 were investigated with respect to their strain induced crystalline morphologies as produced by a tubular uniaxial Film Extrusion process. By holding the process time window constant through the use of fixed melt temperature, line speed, quench height and Film thickness, it was noted that as molecular weight increased, the uniaxial Films produced systematically change from nearly a spherulitic structure to that of an extremely high concentration of fibril nuclei with minimal growth of folded chain lamella developing perpendicular to the fibrils. The systematic variation in the morphology was directly coupled through consideration of the melt process time window in conjunction with the characteristic relaxation time of a given resin at a given temperature. The latter was determined through use of a Carreau–Yasuda analysis of the melt rheological behavior of each resin and this relaxation time, when correlated to the process time, produced a relative Deborah number. It was distinctly shown that when the Deborah number was considerably less than unity, little crystal orientation was observed in the morphological texture whereas in the range of unity, a distinct rise in crystalline orientation occurred leading to fibril nucleation with lamella side growth in the form of the well known row structure morphology. Exceeding a Deborah number of unity led to nearly full crystalline orientation saturation and to a very high concentration of fibril nucleai with relatively few orthogonal lamella observable. The morphological textures were investigated using AFM, WAXS, SALS, SAXS and birefringence. Use of thermal analysis to determine some of the polymorphic character of the PVDF crystal form was also undertaken.

J C Pirkle - One of the best experts on this subject based on the ideXlab platform.

  • a thin shell two phase microstructural model for blown Film Extrusion
    Journal of Rheology, 2010
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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...

  • Maximum-Likelihood Parameter Estimation for the Thin-Shell Quasi-Newtonian Model for a Laboratory Blown Film Extruder
    Industrial & Engineering Chemistry Research, 2010
    Co-Authors: J C Pirkle, Mitsuko Fujiwara, Richard D. Braatz
    Abstract:

    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...

  • A thin-shell two-phase microstructural model for blown Film Extrusion
    Journal of Rheology (1978-present), 2010
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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.

  • Comparison of the Dynamic Thin Shell and Quasi-cylindrical Models for Blown Film Extrusion
    Polymer Engineering and Science, 2004
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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.

  • Dynamic modeling of blown‐Film Extrusion
    Polymer Engineering and Science, 2003
    Co-Authors: J C Pirkle, Richard D. Braatz
    Abstract:

    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.

Amod A. Ogale - One of the best experts on this subject based on the ideXlab platform.

  • Real‐time crystalline orientation measurements during low‐density polyethylene blown Film Extrusion using wide‐angle X‐ray diffraction
    Polymer Engineering and Science, 2012
    Co-Authors: Giriprasath Gururajan, Amod A. Ogale
    Abstract:

    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

  • Molecular orientation evolution during low‐density polyethylene blown Film Extrusion using real‐time Raman spectroscopy
    Journal of Raman Spectroscopy, 2008
    Co-Authors: Giriprasath Gururajan, Amod A. Ogale
    Abstract:

    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.

  • Real-time wide-angle X-ray diffraction during polyethylene blown Film Extrusion
    Polymer Engineering and Science, 2008
    Co-Authors: Giri Gururajan, H. Shan, G. Lickfield, Amod A. Ogale
    Abstract:

    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

  • Online measurements of crystallinity using Raman spectroscopy during blown Film Extrusion of a linear low-density polyethylene
    Polymer Engineering and Science, 2004
    Co-Authors: Srinivas S. Cherukupalli, Amod A. Ogale
    Abstract:

    Real-time, Raman spectroscopic measurements of crystallinity during the blown Film Extrusion of a linear low-density polyethylene (LLDPE) are reported. The take-up ratio (TUR), inflation air pressure, and cooling conditions were varied, and their effect on the development of crystallinity was studied. The results indicate that the crystallization process starts at the freeze line, increases along the Film line, and finally plateaus. It was observed that with changing processing conditions, the differences in the profiles for crystallinity were evident when plotted as a function of time rather than distance along the machine direction. The influence of take-up ratio and bubble inflation air pressure on the development of crystallinity clearly established the role of flow-induced crystallization during Film Extrusion. Polym. Eng. Sci. 44:1484–1490, 2004. © 2004 Society of Plastics Engineers.

James L. White - One of the best experts on this subject based on the ideXlab platform.

  • Crystal structures and orientation development in tubular Film Extrusion of syndiotactic polypropylene and isotactic polypropylene
    Polymer Engineering and Science, 2001
    Co-Authors: Dongman Choi, James L. White
    Abstract:

    The differences in behavior of isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) in tubular Film Extrusion are qualitatively described. The crystalline form and orientation in the Films were characterized using wide-angle X-ray diffraction (WAXD) patterns, pole-figure analysis and birefringence. The sPP Films had the crystalline form of the disordered Form I and the a-crystallographic axis was found to be preferentially oriented in the Film normal direction (ND) under the conditions of biaxial stresses. High transverse orientations were developed in the sPP Films. In the iPP Films, the monoclinic crystalline form was found and the b-crystallographic axis was preferentially oriented in the ND. The birefringence of the Films showed trends very similar to the crystalline orientations characterized by WAXD in both iPP and sPP Films.

  • Instability phenomena in tubular Film, and melt spinning of rheologically characterized high density, low density and linear low density polyethylenes
    Journal of Non-newtonian Fluid Mechanics, 2001
    Co-Authors: Wataru Minoshima, James L. White
    Abstract:

    Abstract An experimental study of instabilities in melt spinning, ribbon drawdown and tubular Film Extrusion of moleculary and rheologically characterized high density (HDPE) low density (LDPE) and linear low density (LLDPE) polyethylenes is presented. The characteristics of the instabilities occuring in these processes are described. The draw resonance instability is found to occur in melt spinning and ribbon drawdown. Special attention is given to tubular Film Extrusion which has received little treatment in the literature. Three distinctive tubular Film instabilities are described. These involve (i) an axisymmetric periodic fluctuation in bubble diameter; (ii) a fluctuation of frostline height and tension; (iii) a helical motion of the bubble. The characteristics and occurrence of these phenomena are discused. In the melt spinning and ribbon drawdown, th LDPE is the most stable and the broad molecular weight distribution HDPEs the most unstable. In tubular Film Extrusion, the LDPEs are again the most stable but the narrower distribution HDPEs and LLDPEs are much more unstable than the broader distribution HDPE. These results are discussed in terms of convected Maxwell model representations.

  • Single and double bubble tubular Film Extrusion of polyethylene 2, 6-naphthalate (PEN)
    Polymer Engineering and Science, 2000
    Co-Authors: Kwangjin Song, James L. White
    Abstract:

    An experimental study of Film formation and structure development of polyethylene 2,6-naphthalate (PEN) in single and double bubble tubular Film Extrusion is presented. PEN was largely stable in Film blowing. The Films produced were characterized with wide angle X-ray diffraction, DSC, and Abbe refractometer techniques. The structure and orientation in the Films varied substantially with process and Film formation history. Single bubbles exhibited polymorphs with considerable levels of orientation, while double bubbles possessed only the extended α-modification. With increasing planar strain, the naphthyl rings on the chain backbone became increasingly aligned parallel to the Film surface. The mechanism of structure evolution in PEN was related to its behavior during the inflation period and compared with that found in polybutylene terephthalate (PBT) and polyethylene terephthalate (PET).

  • Double bubble tubular Film Extrusion of polybutylene terephthalate–polyethylene terephthalate blends
    Polymer Engineering and Science, 2000
    Co-Authors: Kwangjin Song, James L. White
    Abstract:

    A technology has been developed to produce biaxially oriented Films of blends of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) using double bubble tubular Film Extrusion. The mechanical instabilities and the mechanisms associated with their sources of occurrence are described. Bubble stability varies substantially with deformation and composition. The Films have been structurally characterized with wide angle X-ray diffraction and optical techniques. The individual phases in the blends oriented differently. We have proposed a model of crystalline morphology in biaxially oriented PBT/PET blend Films. The structure of the Film is related to processing conditions.

  • Investigation of double bubble tubular Film Extrusion of polyamide 6 and Film structural characteristics
    Polymer Engineering and Science, 1999
    Co-Authors: Sangkeun Rhee, James L. White
    Abstract:

    Biaxially oriented polyamide 6 Films were made by double bubble tubular Film Extrusion. The crystalline character and biaxial orientation of the Films were investigated by measuring (in plane and out of plane) birefringences, IR (infrared) spec' troscopy, and wide angle X-ray diffraction (WAXS) flat Film patterns and pole figures. The samples were also examined by tensile stretching tests in different sampling directions.