The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform
Mari Pihlatie - One of the best experts on this subject based on the ideXlab platform.
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Comparison of static chambers to measure CH4 emissions from soils
Agricultural and Forest Meteorology, 2013Co-Authors: Mari Pihlatie, Jesper Riis Christiansen, Hermanni Aaltonen, Janne F. J. Korhonen, Annika Nordbo, Terhi Rasilo, Giuseppe Benanti, Michael Giebels, Mohamed Helmy, Jatta SheehyAbstract:The static chamber method (non-flow-through-non-steady-state chambers) is the most common method to measure fluxes of methane (CH4) from soils. Laboratory comparisons to quantify errors resulting from chamber design, operation and flux calculation methods are rare. We tested fifteen chambers against four flux levels (FL) ranging from 200 to 2300 μg CH4 m−2 h−1. The measurements were conducted on a Calibration Tank using three quartz sand types with soil porosities of 53% (dry fine sand, S1), 47% (dry coarse sand, S2), and 33% (wetted fine sand, S3). The chambers tested ranged from 0.06 to 1.8 m in height, and 0.02 to 0.195 m3 in volume, 7 of them were equipped with a fan, and 1 with a vent-tube. We applied linear and exponential flux calculation methods to the chamber data and compared these chamber fluxes to the reference fluxes from the Calibration Tank. The chambers underestimated the reference fluxes by on average 33% by the linear flux calculation method (Rlin), whereas the chamber fluxes calculated by the exponential flux calculation method (Rexp) did not significantly differ from the reference fluxes (p < 0.05). The flux under- or overestimations were chamber specific and independent of flux level. Increasing chamber height, area and volume significantly reduced the flux underestimation (p < 0.05). Also, the use of non-linear flux calculation method significantly improved the flux estimation; however, simultaneously the uncertainty in the fluxes was increased. We provide correction factors, which can be used to correct the under- or overestimation of the fluxes by the chambers in the experiment.
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Comparison of different chamber techniques for measuring soil CO2 efflux
Agricultural and Forest Meteorology, 2004Co-Authors: Jukka Pumpanen, Pasi Kolari, Hannu Ilvesniemi, Kari Minkkinen, Timo Vesala, Sini Niinistö, Annalea Lohila, Tuula Larmola, Micaela Morero, Mari PihlatieAbstract:Twenty chambers for measurement of soil CO2 efflux were compared against known CO2 fluxes ranging from 0.32 to 10.01 mumol CO2 m(-2) s(-1) and generated by a specially developed Calibration Tank. Chambers were tested on fine and coarse homogeneous quartz sand with particle sizes of 0.05-0.2 and 0.6 mm, respectively. The effect of soil moisture on chamber measurements was tested by wetting the fine quartz sand to about 25% volumetric water content. Non-steady-state through-flow chambers either underestimated or overestimated fluxes from -21 to +33% depending on the type of chamber and the method of mixing air within the chamber's headspace. However, when results of all systems tested were averaged, fluxes were within 4% of references. Non-steady-state non-through-flow chambers underestimated or overestimated fluxes from -35 to +6%. On average, the underestimation was about 13-14% on fine sand and 4% on coarse sand. When the length of the measurement period was increased, the underestimation increased due to the rising concentration within the chamber headspace, which reduced the diffusion gradient within the soil. Steady-state through-flow chambers worked almost equally well in all sand types used in this study. They overestimated the fluxes on average by 2-4%. Overall, the reliability of the chambers was not related to the measurement principle per se. Even the same chambers, with different collar designs, showed highly variable results. The mixing of air within the chamber can be a major source of error. Excessive turbulence inside the chamber can cause mass flow of CO2 from the soil into the chamber. The chamber headspace concentration also affects the flux by altering the concentration gradient between the soil and the chamber. (Less)
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Comparison of different chamber techniques for measuring soil CO2 efflux
Agricultural and Forest Meteorology, 2004Co-Authors: Jukka Pumpanen, Pasi Kolari, Hannu Ilvesniemi, Kari Minkkinen, Timo Vesala, Sini Niinistö, Annalea Lohila, Tuula Larmola, Micaela Morero, Mari PihlatieAbstract:Twenty chambers for measurement of soil CO2 efflux were compared against known CO2 fluxes ranging from 0.32 to 10.01 mumol CO2 m(-2) s(-1) and generated by a specially developed Calibration Tank. Chambers were tested on fine and coarse homogeneous quartz sand with particle sizes of 0.05-0.2 and 0.6 mm, respectively. The effect of soil moisture on chamber measurements was tested by wetting the fine quartz sand to about 25% volumetric water content. Non-steady-state through-flow chambers either underestimated or overestimated fluxes from -21 to +33% depending on the type of chamber and the method of mixing air within the chamber's headspace. However, when results of all systems tested were averaged, fluxes were within 4% of references. Non-steady-state non-through-flow chambers underestimated or overestimated fluxes from -35 to +6%. On average, the underestimation was about 13-14% on fine sand and 4% on coarse sand. When the length of the measurement period was increased, the underestimation increased due to the rising concentration within the chamber headspace, which reduced the diffusion gradient within the soil. Steady-state through-flow chambers worked almost equally well in all sand types used in this study. They overestimated the fluxes on average by 2-4%. Overall, the reliability of the chambers was not related to the measurement principle per se. Even the same chambers, with different collar designs, showed highly variable results. The mixing of air within the chamber can be a major source of error. Excessive turbulence inside the chamber can cause mass flow of CO2 from the soil into the chamber. The chamber headspace concentration also affects the flux by altering the concentration gradient between the soil and the chamber
Aurélien Carin - One of the best experts on this subject based on the ideXlab platform.
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External Calibration in PA12 tube extrusion
International Polymer Processing, 2006Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:In polyamide 12 (PA12) tube extrusion, Calibration is crucial for the major final properties such as elongation at break or burst pressure. In external Calibration, the extruded tube is pulled through a cylindrical calibrator located in a water Tank under vacuum. A water flow rate is applied at the calibrator inner side, creating a lubricating water layer at the polymer outer surface. A combination of a quenching and a mechanical drawing was highlighted during Calibration by on-line measurements. A subsequent high molecular orientation in the outer tube layers was also featured by X-Ray diffraction and birefringence evaluation in light microscopy. Besides, influence of lubrication level in the sizing-sleeve was investigated by an estimate of the lubricating water layer and a characterization of the tube final surface state in different Calibration conditions. Firstly, we quantitatively showed that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank, DrCAL (ratio between line velocity and velocity at the calibrator entrance). Excellent correlation has been found between tube superficial orientation and DrCAL: a reduced elongation of the polymer in the calibrator leads to a lower level of superficial orientation. Secondly, two kinds of surface defects were detected on the tubes by light microscopy and microtopography. At last, several correlations were featured with mechanical properties. Elongation at break was found to strongly depend on the molecular orientation resulting from Calibration. Moreover, origin of rupture was investigated during tensile testing in light microscopy. We emphasized that surface defects alignments perpendicular to the extrusion initiate the rupture by creating a significant crack via coalescence of initial defects. Thus, microstructure, surface state and tensile properties can be controlled by fitting the Calibration parameters to improve lubrication and reduce the draw ratio in calibrator.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Abstract In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entranc...
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External Calibration in PA12 tube extrusion: Part I: On-line draw ratio measurement and lubrication estimate for determination of tensile properties
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, D SilagyAbstract:In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the Calibration Tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during Calibration. We showed quantitatively that using the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main Calibration parameters to improve lubrication and restrict draw ratio in the Calibration Tank.
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External Calibration in PA12 tube extrusion - Part II: Relations between molecular orientation, tensile properties and polymer drawing during Calibration
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, Calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the Calibration Tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from Calibration conditions.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, D SilagyAbstract:AbstractIn PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the Calibration Tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during Calibration. We showed quantitatively that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main Calibration parameters to improve lubrication and restrict draw ratio in the Calibration Tank.
Nicolas Amouroux - One of the best experts on this subject based on the ideXlab platform.
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External Calibration in PA12 tube extrusion
International Polymer Processing, 2006Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:In polyamide 12 (PA12) tube extrusion, Calibration is crucial for the major final properties such as elongation at break or burst pressure. In external Calibration, the extruded tube is pulled through a cylindrical calibrator located in a water Tank under vacuum. A water flow rate is applied at the calibrator inner side, creating a lubricating water layer at the polymer outer surface. A combination of a quenching and a mechanical drawing was highlighted during Calibration by on-line measurements. A subsequent high molecular orientation in the outer tube layers was also featured by X-Ray diffraction and birefringence evaluation in light microscopy. Besides, influence of lubrication level in the sizing-sleeve was investigated by an estimate of the lubricating water layer and a characterization of the tube final surface state in different Calibration conditions. Firstly, we quantitatively showed that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank, DrCAL (ratio between line velocity and velocity at the calibrator entrance). Excellent correlation has been found between tube superficial orientation and DrCAL: a reduced elongation of the polymer in the calibrator leads to a lower level of superficial orientation. Secondly, two kinds of surface defects were detected on the tubes by light microscopy and microtopography. At last, several correlations were featured with mechanical properties. Elongation at break was found to strongly depend on the molecular orientation resulting from Calibration. Moreover, origin of rupture was investigated during tensile testing in light microscopy. We emphasized that surface defects alignments perpendicular to the extrusion initiate the rupture by creating a significant crack via coalescence of initial defects. Thus, microstructure, surface state and tensile properties can be controlled by fitting the Calibration parameters to improve lubrication and reduce the draw ratio in calibrator.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Abstract In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entranc...
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External Calibration in PA12 tube extrusion - Part II: Relations between molecular orientation, tensile properties and polymer drawing during Calibration
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, Calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the Calibration Tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from Calibration conditions.
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Part II: Relations between Molecular Orientation, Tensile Properties and Polymer Drawing during Calibration
2005Co-Authors: Aurélien Carin, Gaelle Bellet, Nicolas Amouroux, Michel Vincent, Bernard Monasse, Sophia AntipolisAbstract:Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r, z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, Calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the Calibration Tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from Calibration conditions.
Michel Vincent - One of the best experts on this subject based on the ideXlab platform.
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External Calibration in PA12 tube extrusion
International Polymer Processing, 2006Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:In polyamide 12 (PA12) tube extrusion, Calibration is crucial for the major final properties such as elongation at break or burst pressure. In external Calibration, the extruded tube is pulled through a cylindrical calibrator located in a water Tank under vacuum. A water flow rate is applied at the calibrator inner side, creating a lubricating water layer at the polymer outer surface. A combination of a quenching and a mechanical drawing was highlighted during Calibration by on-line measurements. A subsequent high molecular orientation in the outer tube layers was also featured by X-Ray diffraction and birefringence evaluation in light microscopy. Besides, influence of lubrication level in the sizing-sleeve was investigated by an estimate of the lubricating water layer and a characterization of the tube final surface state in different Calibration conditions. Firstly, we quantitatively showed that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank, DrCAL (ratio between line velocity and velocity at the calibrator entrance). Excellent correlation has been found between tube superficial orientation and DrCAL: a reduced elongation of the polymer in the calibrator leads to a lower level of superficial orientation. Secondly, two kinds of surface defects were detected on the tubes by light microscopy and microtopography. At last, several correlations were featured with mechanical properties. Elongation at break was found to strongly depend on the molecular orientation resulting from Calibration. Moreover, origin of rupture was investigated during tensile testing in light microscopy. We emphasized that surface defects alignments perpendicular to the extrusion initiate the rupture by creating a significant crack via coalescence of initial defects. Thus, microstructure, surface state and tensile properties can be controlled by fitting the Calibration parameters to improve lubrication and reduce the draw ratio in calibrator.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Abstract In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entranc...
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External Calibration in PA12 tube extrusion: Part I: On-line draw ratio measurement and lubrication estimate for determination of tensile properties
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, D SilagyAbstract:In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the Calibration Tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during Calibration. We showed quantitatively that using the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main Calibration parameters to improve lubrication and restrict draw ratio in the Calibration Tank.
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External Calibration in PA12 tube extrusion - Part II: Relations between molecular orientation, tensile properties and polymer drawing during Calibration
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, Calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the Calibration Tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from Calibration conditions.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, D SilagyAbstract:AbstractIn PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the Calibration Tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during Calibration. We showed quantitatively that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main Calibration parameters to improve lubrication and restrict draw ratio in the Calibration Tank.
Gaelle Bellet - One of the best experts on this subject based on the ideXlab platform.
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External Calibration in PA12 tube extrusion
International Polymer Processing, 2006Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:In polyamide 12 (PA12) tube extrusion, Calibration is crucial for the major final properties such as elongation at break or burst pressure. In external Calibration, the extruded tube is pulled through a cylindrical calibrator located in a water Tank under vacuum. A water flow rate is applied at the calibrator inner side, creating a lubricating water layer at the polymer outer surface. A combination of a quenching and a mechanical drawing was highlighted during Calibration by on-line measurements. A subsequent high molecular orientation in the outer tube layers was also featured by X-Ray diffraction and birefringence evaluation in light microscopy. Besides, influence of lubrication level in the sizing-sleeve was investigated by an estimate of the lubricating water layer and a characterization of the tube final surface state in different Calibration conditions. Firstly, we quantitatively showed that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank, DrCAL (ratio between line velocity and velocity at the calibrator entrance). Excellent correlation has been found between tube superficial orientation and DrCAL: a reduced elongation of the polymer in the calibrator leads to a lower level of superficial orientation. Secondly, two kinds of surface defects were detected on the tubes by light microscopy and microtopography. At last, several correlations were featured with mechanical properties. Elongation at break was found to strongly depend on the molecular orientation resulting from Calibration. Moreover, origin of rupture was investigated during tensile testing in light microscopy. We emphasized that surface defects alignments perpendicular to the extrusion initiate the rupture by creating a significant crack via coalescence of initial defects. Thus, microstructure, surface state and tensile properties can be controlled by fitting the Calibration parameters to improve lubrication and reduce the draw ratio in calibrator.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Abstract In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entranc...
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External Calibration in PA12 tube extrusion: Part I: On-line draw ratio measurement and lubrication estimate for determination of tensile properties
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, D SilagyAbstract:In PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the Calibration Tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during Calibration. We showed quantitatively that using the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main Calibration parameters to improve lubrication and restrict draw ratio in the Calibration Tank.
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External Calibration in PA12 tube extrusion - Part II: Relations between molecular orientation, tensile properties and polymer drawing during Calibration
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, Nicolas AmourouxAbstract:Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, Calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the Calibration Tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from Calibration conditions.
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External Calibration in PA12 Tube Extrusion
International Polymer Processing, 2005Co-Authors: Aurélien Carin, Gaelle Bellet, Michel Vincent, Jean-marc Haudin, Bernard Monasse, D SilagyAbstract:AbstractIn PA12 tube extrusion, Calibration or sizing is the key step of the process that affects subsequent mechanical properties. The extruded tube is pulled through a cylindrical calibrator under vacuum. A water flow rate is applied at the inner side of the calibrator, creating a lubricant water layer at the polymer outer surface. The scope of this article is to show how this lubrication influences the elongation at break of tubes through drawing kinematics of the polymer. Lubricant water layer thickness measurements and on-line video recording have been employed to monitor the lubrication dependence of the velocity profiles from the extruder die to the end of calibrator. Velocities were measured through three independent innovative methods and thirty-two Calibration conditions have been carried out to validate our work. Three main Calibration parameters were found to determine the water layer thickness: the level of vacuum applied in the Calibration Tank, the water flow rate at the calibrator entrance, and the line speed. The influence of each parameter on lubrication level was found out. Simultaneously, the draw ratio in the Calibration Tank was deduced from velocity profiles. This parameter was found to affect tensile properties and to depend strongly on the level of lubrication during Calibration. We showed quantitatively that rising the water layer thickness leads to a diminution of the draw ratio in the Calibration Tank and an increase of the elongation at break. This implies that we are now able to optimize tensile properties by fitting the main Calibration parameters to improve lubrication and restrict draw ratio in the Calibration Tank.
