.. Validation-du-modèle-rhéologique, 93 ? Validation expérimentale, 93 ? Test statistique de Fisher-Snedecor . . . . . . . . . . . . 94

. La-deuxième-phase-de-l, analyse multicritère a été conduite en développant un système d'aide à la décision avec pour objectif de dégager la meilleure solution parmi l'ensemble de compromis acceptables déterminé dans la première étape. Ceci a permis, compte tenu de préférences prédéfinies, de présenter des recommandations concernant les conditions opératoires pour l'homogénéisation optimale de PE bimodaux tout en tenant compte du coût énergétique que représente l'opération

A. Ajji and L. A. Et-utracki, Interphase and compatibilization of polymer blends, Polymer Engineering & Science, vol.33, issue.12, pp.1574-1585, 1996.
DOI : 10.1002/masy.19940830110

S. Areerat, T. Nagata, and M. Et-oshima, Measurement and prediction of LDPE/CO2 solution viscosity, Polymer Engineering & Science, vol.40, issue.11, pp.2234-2245, 2002.
DOI : 10.1002/pen.11113

F. Bicking, C. Fonteix, J. Corriou, and I. Marc, Global optimization by artificial life : a new technique using genetic population evolution, RAIRO - Operations Research, vol.28, issue.1, pp.23-36, 1994.
DOI : 10.1016/0098-1354(90)80020-C

B. Bourry and B. Et-favis, Morphology development in a polyethylene/polystyrene binary blend during twin-screw extrusion, Polymer, vol.39, issue.10, pp.1851-1856, 1998.
DOI : 10.1016/S0032-3861(97)00397-2

J. Brans and B. Et-mareschal, Prométhée ? Gaia : Une Méthodologie d'Aide à la Décision en Présence de Critères Multiples, Ellipses, 2002.

J. P. Brans and P. Et-vincke, A preference ranking organization method, Management Science, issue.6, pp.31647-656, 1985.

J. S. Chiou, J. W. Barlow, and D. R. Paul, Plasticization of glassy polymers by CO2, Journal of Applied Polymer Science, vol.30, issue.6, pp.2633-2642, 1985.
DOI : 10.1002/app.1985.070300626

A. A. Clifford, E. Kiran, J. M. Et-levelt-sengers, and . Éditeurs, Reactions in supercritical fluids Supercritical Fluids : Fundamentals for Application, pp.449-479, 1994.

J. M. Desimone, Z. Guan, and C. S. Et-elsbernd, Synthesis of Fluoropolymers in Supercritical Carbon Dioxide, Science, vol.257, issue.5072, pp.945-947, 1992.
DOI : 10.1126/science.257.5072.945

A. K. Doolittle, Studies in Newtonian Flow. II. The Dependence of the Viscosity of Liquids on Free???Space, Journal of Applied Physics, vol.18, issue.12, pp.1471-1475, 1951.
DOI : 10.1039/tf9231900006

M. Dupire, T. Lindt, and G. Et-debras, Improved processing of bimodal polymers, 2003.

R. T. Eckenrode and M. D. Références-bibliographiques-elkovitch, Weighting Multiple Criteria, Thèse de doctorat, pp.180-192, 1965.
DOI : 10.1287/mnsc.12.3.180

M. D. Elkovitch, J. Lee, and D. L. Et-tomasko, Effect of supercritical carbon dioxide on morphology development during polymer blending, Polymer Engineering & Science, vol.146, issue.8, pp.401850-1861, 2000.
DOI : 10.1002/pen.11317

M. D. Elkovitch, D. L. Tomasko, and L. J. Et-lee, Supercritical carbon dioxide assisted blending of polystyrene and poly(methyl methyacrylate), Polymer Engineering & Science, vol.11, issue.10, pp.2075-2084, 1999.
DOI : 10.1002/(SICI)1097-4628(19960124)59:4<707::AID-APP16>3.0.CO;2-M

M. D. Elkovitch, L. J. Lee, and D. L. Et-tomasko, Effect of supercritical carbon dioxide on PMMA/rubber and polystyrene/rubber blending: Visosity ratio and phase inversion, Polymer Engineering & Science, vol.30, issue.12, pp.412108-2125, 2001.
DOI : 10.1002/pen.10906

R. A. Fisher, Statistical Methods for Research Workers, 14 th Ed, 1970.

P. J. Flory, Thermodynamics of High Polymer Solutions, The Journal of Chemical Physics, vol.9, issue.8, pp.660-661, 1941.
DOI : 10.1039/TF9403500619

C. Fonteix, F. Bicking, E. Perrin, and I. Marc, Haploid and diploid algorithms, a new approach for global optimization: compared performances, International Journal of Systems Science, vol.57, issue.10, pp.1919-1933, 1995.
DOI : 10.1007/BF02592070

C. Fonteix, S. Massebeuf, F. Pla, and L. N. Et-kiss, Multicriteria optimization of an emulsion polymerization process, European Journal of Operational Research, vol.153, issue.2, pp.350-359, 2004.
DOI : 10.1016/S0377-2217(03)00157-7

A. Garg, E. Gulari, and C. W. Et-manke, Thermodynamics of Polymer Melts Swollen with Supercritical Gases, Macromolecules, vol.27, issue.20, pp.5643-5653, 1994.
DOI : 10.1021/ma00098a019

R. Gendron and L. Et-daigneault, Continuous extrusion of microcellular polycarbonate, Polymer Engineering & Science, vol.31, issue.7, pp.1361-1377, 2003.
DOI : 10.1002/pen.10116

L. J. Gerhardt, C. W. Manke, and E. Et-gulari, Rheology of polydimethylsiloxane swollen with supercritical carbon dioxide, Journal of Polymer Science Part B: Polymer Physics, vol.35, issue.3, pp.523-534, 1997.
DOI : 10.1002/(SICI)1099-0488(199702)35:3<523::AID-POLB11>3.0.CO;2-J

E. Ginsburger, Définition et mise au point d'une méthodologie pour l'extrapolation de procédé de copolymérisation en émulsion, Thèse de doctorat, 2001.

S. K. Goel and E. J. Et-beckman, Plasticization of poly(methyl methacrylate) (PMMA) networks by supercritical carbon dioxide, Polymer, vol.34, issue.7, pp.1410-1417, 1993.
DOI : 10.1016/0032-3861(93)90853-3

H. P. Grace, DISPERSION PHENOMENA IN HIGH VISCOSITY IMMISCIBLE FLUID SYSTEMS AND APPLICATION OF STATIC MIXERS AS DISPERSION DEVICES IN SUCH SYSTEMS, Chemical Engineering Communications, vol.10, issue.3-6, pp.3-6225, 1982.
DOI : 10.1002/aic.690150512

S. Greco, B. Matarazzo, and R. Et-slowinski, Rough sets theory for multicriteria decision analysis, European Journal of Operational Research, vol.129, issue.1, pp.1-47, 2001.
DOI : 10.1016/S0377-2217(00)00167-3

Z. Guan, J. R. Combes, Y. Z. Menceloglu, and J. M. Et-desimone, Homogeneous free radical polymerizations in supercritical carbon dioxide: 2. Thermal decomposition of 2,2'-azobis(isobutyronitrile), Macromolecules, vol.26, issue.11, pp.262663-2669, 1993.
DOI : 10.1021/ma00063a003

J. B. Hannay and J. Et-hogarth, On the Solubility of Solids in Gases, Proceedings of the Royal Society of London, vol.29, issue.196-199, pp.324-326, 1879.
DOI : 10.1098/rspl.1879.0054

H. J. Hayes and T. J. Et-mccarthy, Maleation of polyolefins using supercritical carbon dioxide, Polymer Preprints, vol.38, issue.2, pp.426-427, 1997.

H. J. Hayes and T. J. Et-mccarthy, Maleation of poly(4-methyl-1-pentene) using supercritical carbon dioxide, Macromolecules, issue.15, pp.314813-4819, 1998.

H. Hermann and D. Et-rath, Method and apparatus for removing impurities from plastics, 1988.

S. Hoppe, C. Schrauwen, C. Fonteix, and F. Et-pla, Experimental study of maleic anhydride grafting on polypropylene by reactive extrusion under supercritical conditions, DECHEMA Monographs, vol.138, pp.123-130, 2004.

M. L. Huggins, Solutions of Long Chain Compounds, The Journal of Chemical Physics, vol.9, issue.5, p.440, 1941.
DOI : 10.1002/hlca.194002301130

W. Kaminsky, H. R. Polyolefins-kricheldorf, and . Éditeur, Handbook of Polymer Synthesis ? Part A, pp.1-76, 1992.

J. L. Kendall, D. A. Canelas, J. L. Young, and J. M. Et-desimone, Polymerizations in Supercritical Carbon Dioxide, Chemical Reviews, vol.99, issue.2, pp.543-563, 1999.
DOI : 10.1021/cr9700336

M. Kimura, T. Saeki, and M. Suzuki, Removal of low molecular weight components from polyesters, Japanese Patent #03 217 422, 1991.

E. Kiran, Polymerization and Polymer Modification Reactions in Near and Supercritical Fluids, Proceedings of the 1 st International High Pressure Chemical Engineering Conference, pp.3-12, 1999.
DOI : 10.1007/978-94-011-3929-8_10

J. G. Knudsen, H. C. Hottel, A. F. Sarofim, P. C. Wankat, and K. S. Et-knaebel, Heat and mass transfer, section 5 éditeurs, Perry's Chemical Engineers' Handbook, 7 th Ed, pp.1-79, 1997.

H. Knuuttila, A. Lehtinen, and A. Et-nummila-pakarinen, Advanced Polyethylene Technologies???Controlled Material Properties, Advances in Polymer Science, vol.169, pp.13-27, 2004.
DOI : 10.1007/b13519

G. Kokturk and S. M. Et-howdle, Supercritical fluids : New solvents for polymer synthesis and polymer processing, DECHEMA Monographien, vol.137, issue.1, pp.79-98, 2001.

V. J. Krukonis, Processing of polymers with supercritical fluids, Polymer News, vol.11, issue.1, pp.7-16, 1985.

S. Krupinski and J. Et-mcqueen, Devolatilization of polymers or polymer blends by injecting a supercritical fluid at polymer melting temperature, 1997.

C. Kwag, C. W. Manke, and E. Et-gulari, Rheology of molten polystyrene with dissolved supercritical and near-critical gases, Journal of Polymer Science Part B: Polymer Physics, vol.27, issue.19, pp.2771-2781, 1999.
DOI : 10.1021/ma00080a008

J. K. Lee and C. Et-han, Evolution of polymer blend morphology during compounding in a twin-screw extruder, Polymer, vol.41, issue.5, pp.1799-1815, 2000.
DOI : 10.1016/S0032-3861(99)00325-0

M. Lee, Extrusion of Polymers and Polymer Blends with Supercritical Carbon Dioxide, Thèse de doctorat, 2000.

M. Lee, C. B. Park, and C. Et-tzoganakis, Measurements and modeling of PS/supercritical CO2 solution viscosities, Polymer Engineering & Science, vol.4, issue.1, pp.99-109, 1999.
DOI : 10.1007/978-94-009-2163-4

M. Lee, C. Tzoganakis, and C. B. Park, Extrusion of PE/PS blends with supercritical carbon dioxide, Polymer Engineering & Science, vol.53, issue.7, pp.1112-1120, 1998.
DOI : 10.1002/pen.10278

A. Luciani and L. A. Et-utracki, The Extensional Flow Mixer, EFM, International Polymer Processing, vol.11, issue.4, pp.299-309, 1996.
DOI : 10.3139/217.960299

A. V. Machado, J. A. Covas, and M. Et-van-duin, Evolution of morphology and of chemical conversion along the screw in a corotating twin-screw extruder, Journal of Applied Polymer Science, vol.32, issue.1, pp.135-141, 1999.
DOI : 10.3139/217.970011

C. W. Macosko, Rheology ? Principles, Measurements, and Applications, 1994.

P. Maréchal, Producing bimodal polyethylene resins for pipes and films, 2002.

J. E. Martini-vvedensky, N. P. Suh, and F. A. Et-waldman, Microcellular closed cell foams and their method of manufacture, 1984.

S. Massebeuf, Optimisation multicritère de procédés discontinus d'homopolymérisation et de copolymérisation en émulsion, Thèse de doctorat, Institut National Polytechnique de Lorraine, 2000.

M. A. Mchugh and V. J. Et-krukonis, Supercritical Fluid Extraction : Principles and Practices, 2 nd Ed, 1994.

M. Meller, A. Luciani, and J. E. Et-manson, Mixing Homologous High Viscosity Ratio Polymer Blends in Converging Flow, International Polymer Processing, vol.14, issue.3, pp.221-227, 1999.
DOI : 10.3139/217.1549

X. Q. Nguyen, L. A. Et-utracki, I. Nieuwoudt, C. Crause, and M. Du-rand, Extensional flow mixer. US Patent #5 451 106 Oligomer fractionation with supercritical fluids, The Journal of Supercritical Fluids, vol.24, issue.1, pp.47-55, 1995.

J. Oh and J. Et-lindt, A novel couette viscometer for polymer solutions in supercritical fluids, Proceedings of the SPE ANTEC '02, pp.1920-1923, 2002.

V. Pareto, Cours d'Économie Politique, Rouge, p.1896
DOI : 10.3917/droz.paret.1964.01

C. B. Park and N. P. Suh, Filamentary extrusion of microcellular polymers using a rapid decompressive element, Polymer Engineering & Science, vol.24, issue.1, pp.34-48, 1996.
DOI : 10.5254/1.3535991

O. Piernot, Étude d'un procédé de dévolatilisation de traces d'anhydride maléique au sein d'une matrice polypropylène à l'aide d'une extrudeuse bivis, Thèse de doctorat, 2002.

A. Plochocki, S. Dagli, and R. Et-andrews, The interface in binary mixtures of polymers containing a corresponding block copolymer: Effects of industrial mixing processes and of coalescence, Polymer Engineering and Science, vol.26, issue.12, pp.741-752, 1990.
DOI : 10.1007/978-94-009-4185-4_55

F. Pukelsheim, Optimal Design of Experiments, 1993.
DOI : 10.1137/1.9780898719109

B. Rabinowitsch, The viscosity and elasticity of sols, Zeitschrift für physikalische Chemie, pp.1-26, 1929.

K. S. Raju and C. R. Et-pillai, Multicriterion decision making in performance evaluation of an irrigation system, European Journal of Operational Research, vol.112, issue.3, pp.479-488, 1999.
DOI : 10.1016/S0377-2217(98)00007-1

R. C. Reid, J. M. Prausnitz, and B. Et-polig, The Properties of Liquids and Gases, 4 th Ed, 1987.

T. Rische, U. Burkhardt, M. Stephan, and P. Et-heidemeyer, Method to Evaluate the Homogenization of Bimodal Polyethylene in a Co-Rotating Twin Screw Extruder, Pourdeyhimi, B., éditeur, Imaging and Image Analysis Applications for Plastics, pp.53-58, 1999.
DOI : 10.1016/B978-188420781-5.50008-5

S. S. Rizvi, S. J. Mulvaney, and A. S. Et-sokhey, The combined application of supercritical fluid and extrusion technology, Trends in Food Science & Technology, vol.6, issue.7, pp.232-240, 1995.
DOI : 10.1016/S0924-2244(00)89084-6

M. S. Roby and N. Et-totakura, Purification of bioabsorbable polymers using supercritical fluid extraction, 1995.

P. A. Rodgers, Pressure???volume???temperature relationships for polymeric liquids: A review of equations of state and their characteristic parameters for 56 polymers, Journal of Applied Polymer Science, vol.48, issue.6, pp.1061-1080, 1993.
DOI : 10.1002/app.1993.070480613

A. Rousseau and J. M. Et-martel, Environmental assessment of an electric transmission line project : A MCDM method Applying Multiple Criteria Aid for Decision to Environmental Management, pp.163-165, 1994.

B. Roy, Électre III : Algorithme de surclassement basé sur une représentation floue des préférences en présence de critères multiples, Cahier du CERO, vol.20, issue.1, pp.43-67, 1978.

B. Roy and D. Et-bouyssou, Aide Multicritère à la Décision : Méthodes et Cas, Economica, 1993.

J. R. Royer, Y. J. Gay, J. M. Desimone, and S. A. Et-khan, High-pressure rheology of polystyrene melts plasticized with CO 2 : Experimental measurement and predictive scaling relationships, Journal of Polymer Science : Part B : Polymer Physics, issue.23, pp.38-3168, 2000.

T. L. Saaty, Rank from comparisons and from ratings in the analytic hierarchy/network processes, European Journal of Operational Research, vol.168, issue.2, pp.557-570, 2006.
DOI : 10.1016/j.ejor.2004.04.032

I. C. Sanchez and R. H. Et-lacombe, An elementary molecular theory of classical fluids. Pure fluids, The Journal of Physical Chemistry, vol.80, issue.21, pp.2352-2362, 1976.
DOI : 10.1021/j100562a008

I. C. Sanchez and R. H. Et-lacombe, Statistical thermodynamics of fluid mixtures, Journal of Physical Chemistry, vol.80, issue.23, pp.2568-2580, 1976.

J. Scheirs, L. L. Böhm, J. C. Boot, and P. S. Et-leevers, PE100 resins for pipe applications : Continuing the development into the 21st century, Trends in Polymer Science, vol.4, issue.12, pp.408-415, 1996.

K. M. Scholsky, Process polymers with supercritical fluids, Chemtech, pp.750-757, 1987.

C. E. Scott and C. W. Et-macosko, Model experiments concerning morphology development during the initial stages of polymer blending, Polymer Bulletin, vol.39, issue.3, pp.341-348, 1991.
DOI : 10.1007/BF00587979

Y. Shieh, J. Su, G. Manivannan, P. H. Lee, S. P. Sawan et al., Interaction of supercritical carbon dioxide with polymers. I. Crystalline polymers, Journal of Applied Polymer Science, vol.59, issue.4, pp.695-705, 1996.
DOI : 10.1002/(SICI)1097-4628(19960124)59:4<695::AID-APP15>3.0.CO;2-P

Y. Shieh, J. Su, G. Manivannan, P. H. Lee, S. P. Sawan et al., Interaction of supercritical carbon dioxide with polymers. II. Amorphous polymers, Journal of Applied Polymer Science, vol.59, issue.4, pp.707-717, 1996.
DOI : 10.1002/(SICI)1097-4628(19960124)59:4<707::AID-APP16>3.0.CO;2-M

G. W. Snedecor and W. G. Et-cochran, Statistical Methods, 8 t h Ed, 1989.

U. Sundararaj, C. Macosko, and R. Et-rolando, Morphology development in polymer blends, Polymer Engineering and Science, vol.247, issue.24, pp.1814-1823, 1992.
DOI : 10.1098/rspa.1959.0196

Y. Susaka, Mixing device, 1982.

J. Thibault, R. Lanouette, C. Fonteix, and L. N. Et-kiss, Multicriteria Optimization of a High-Yield Pulping Process, The Canadian Journal of Chemical Engineering, vol.17, issue.1, pp.897-902, 2002.
DOI : 10.1002/cjce.5450800512

J. Thibault, D. Taylor, C. Yanofsky, R. Lanouette, C. Fonteix et al., Multicriteria optimization of a high yield pulping process with rough sets, Chemical Engineering Science, vol.58, issue.1, pp.203-213, 2003.
DOI : 10.1016/S0009-2509(02)00470-0

K. Ute, N. Miyatake, and K. Et-hatada, Glass transition temperature and melting temperature of uniform isotactic and syndiotactic poly(methyl methacrylate)s from 13mer to 50mer, Polymer, vol.36, issue.7, pp.1415-1419, 1995.
DOI : 10.1016/0032-3861(95)95919-R

L. A. Utracki, Polymer Blends Handbook. Kluwer, 2002.

L. A. Utracki and Z. H. Shi, Development of polymer blend morphology during compounding in a twin-screw extruder. Part I: Droplet dispersion and coalescence?a review, Polymer Engineering and Science, vol.33, issue.49, pp.1824-1833, 1992.
DOI : 10.1002/masy.19910480117

D. W. Van-krevelen, Properties of Polymers : Their Estimation and Correlation with Chemical Structure, 1976.

B. Vergnes and M. Chapet, Procédés d'extrusion bivis, 2001.

J. C. Via, C. L. Braue, and L. Taylor, Supercritical Fluid Fractionation of a Low Molecular Weight, High-Density Polyethylene Wax Using Carbon Dioxide, Propane, and Propane-Modified Carbon Dioxide, Analytical Chemistry, vol.66, issue.5, pp.603-609, 1994.
DOI : 10.1021/ac00077a005

H. M. Wadsworth and . Éditeur, Handbook of Statistical Methods, 1990.

J. J. Watkins and T. J. Et-mccarthy, Polymerization of Styrene in Supercritical CO2-Swollen Poly(chlorotrifluoroethylene), Macromolecules, vol.28, issue.12, pp.4067-4074, 1995.
DOI : 10.1021/ma00116a004

M. L. Williams, R. F. Landel, and J. Et-ferry, The Temperature Dependence of Relaxation Mechanisms in Amorphous Polymers and Other Glass-forming Liquids, Journal of the American Chemical Society, vol.77, issue.14, pp.773701-3707, 1955.
DOI : 10.1021/ja01619a008

R. R. Yager, On ordered weighted averaging aggregation operators in multicriteria decisionmaking, IEEE Transactions on Systems, Man, and Cybernetics, vol.18, issue.1, pp.183-190, 1988.
DOI : 10.1109/21.87068

K. Yang, S. Lee, and J. Et-oh, Effects of viscosity ratio and compatibilizers on the morphology and mechanical properties of polycarbonate/acrylonitrile-butadiene-styrene blends, Polymer Engineering & Science, vol.66, issue.9, pp.1667-1677, 1999.
DOI : 10.1002/pen.11561

K. Yasuda, R. C. Armstrong, and R. E. Et-cohen, Shear flow properties of concentrated solutions of linear and star branched polystyrenes, Rheologica Acta, vol.28, issue.2, pp.163-178, 1981.
DOI : 10.1007/BF01513059

M. Yoshida, Removal of slightly volatile substances from thermoplastic resins, Japanese Patent #11 292 921, 1999.

B. Zusatz, Contributions à la caractérisation en ligne de l'élaboration de mélanges de polymères réactifs dans une extrudeuse bivis, Thèse de doctorat, 2001.

A. Figure, Profil de vis n° 4 33, pp.50-50

A. Figure, Profil de vis n° 6 33, pp.17-17

A. Figure, Profil de vis n° 10 17, pp.17-1750

A. Figure, Profil de vis n° 11 33, pp.33-50

A. Annexe, Profils de vis 33