Abstract
In polyamide 12 tube extrusion, calibration is the key step of the process that affects the subsequent mechanical properties. In previous work it has been shown that according to the calibration conditions, a very oriented skin layer may be created, which has been correlated to an important decrease of elongation at break. In the present paper we develop a thermomechanical model which consists of two parts: a viscoelastic mechanical model for the calculation of stresses and a thermal model for the determination of the temperature field. Three types of inputs are necessary: processing parameters, material data (e. g., crystallization kinetics and rheology in the melt, the solid state and the transition zone) and heat transfer coefficients to describe the heat exchanges along the extrusion line. The model allows us to propose a physical interpretation of the oriented layer. During cooling high axial stresses are frozen in the first solidified layers. They induce a plastic deformation of the polymer leading to a high level of orientation in the outer zones.
References
Carin, A., “Etude Expérimentale et Modélisation Thermomécanique de l'Etape de Calibration dans le Procédé d'Extrusion de Tubes en Polyamide 12”, Thesis, Ecole des Mines de Paris, France (2005)Search in Google Scholar
Carin, A., et al., “External Calibration in PA12 Tube Extrusion. I. On-Line Draw Ratio Measurement and Lubrication Estimate for Determination of Tensile Properties”, Int. Polym. Proc., 20, 296–304 (2005)Search in Google Scholar
Carin, A., et al., “External Calibration in PA12 Tube Extrusion. II. Relations between Molecular Orientation, Tensile Properties and Polymer Drawing during Calibration”, Int. Polym. Proc., 20, 305–311 (2005)Search in Google Scholar
Carin, A., et al., “External Calibration in PA12 Tube Extrusion. Understand the Influence of Calibration on Microstructure and Surface State to Improve Mechanical Properties”, Int. Polym. Proc., 21, 70–80 (2006)Search in Google Scholar
Cotto, D., et al., “Cast Film Extrusion of Polypropylene Films”, Int. Polym. Proc., 4, 103–113 (1989)Search in Google Scholar
Devisme, S., et al., “Numerical Simulation of Extrusion Coating. Contribution to the Understanding of Adhesion Mechanisms between Grafted Polypropylene and Aluminium”, Int. Polym. Proc., 22, 90–104 (2007)Search in Google Scholar
Duffo, P., et al., “Cast Film Extrusion of Polypropylene. Thermomechanical and Physical Aspects”, J. Polym. Eng., 10, 151–229 (1991)10.1515/POLYENG.1991.10.1-3.151Search in Google Scholar
Dynamit Nobel AG, GB Patent 1 529 370 (1975)Search in Google Scholar
Gas Injection Ltd., GB Patent 2 354 965 (1999)10.1016/S0140-6736(99)90203-9Search in Google Scholar
Gneuss, D., DE Patent 3 243 140 (1982)10.1016/0172-2190(81)90180-0Search in Google Scholar
Labaig, J.-J., et al., “Extrusion Rilsan à Grande Vitesse”, Project Report, Centre d'Etude de Recherche et Développement d'Arkema, Serquigny, France (1986)Search in Google Scholar
Magnet, C., “Cristallisation d'un Polyamide 66 Utilisé en Filage Textile. Influence d'un Ecoulement”, Thesis, Ecole des Mines de Paris, France (1993)Search in Google Scholar
Mitsui Petrochemical Industries, US Patent 4 159 889 (1973)Search in Google Scholar
Parant, O., “Etude Expérimentale et Calcul des Contraintes Résiduelles dans des Tubes Extrudés en Polyéthylène”, Thesis, Ecole des Mines de Paris, France (2002)Search in Google Scholar
Paris, A., “Influence des Conditions de Filage sur les Propriétés Physiques et Mécaniques de Fibres de Polypropylène”, Thesis, Ecole des Mines de Paris, France (1992)Search in Google Scholar
Piorkowska, E., et al., “Critical Assessment of Overall Crystallization Kinetics Theories and Predictions”, Prog. Polym. Sci., 31, 549–575 (2006)10.1016/j.progpolymsci.2006.05.001Search in Google Scholar
Stanisic, M., McKinley, R. M., “A Note on Thermal Stresses in Hollow Cylinders”, Ing. Archiv, 27, 227–241 (1959)10.1007/BF00538344Search in Google Scholar
Trostel, R., Wärmespannungen in Hohlzylindern mit temperaturabhängigen Stoffwerten“, Ing. Archiv, 26, 134–142 (1958)10.1007/BF00535731Search in Google Scholar
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