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«Doctorat ParisTech THÈSE pour obtenir le grade de docteur délivré par l’École Nationale Supérieure d'Arts et Métiers Spécialité “ ...»

-- [ Page 1 ] --

2014-ENAM-0017

École doctorale n° 432 : Sciences des Métiers de l’Ingénieur

Doctorat ParisTech

THÈSE

pour obtenir le grade de docteur délivré par

l’École Nationale Supérieure d'Arts et Métiers

Spécialité “ Mécanique - Matériaux ”

présentée et soutenue publiquement par

Alexandre FRANCOIS-HEUDE

le 19 Juin 2014

KINETIC MODELING OF THE POLYPROPYLENE PHOTOTHERMAL

OXIDATION

Directeur de thèse : Xavier COLIN Co-encadrement de la thèse : Emmanuel RICHAUD Jury T Professeur, Université Blaise-Pascal, Clermont-Ferrand Président M. Jean-Luc GARDETTE Directeur de Recherche, Polymer Institute, Bratislava Rapporteur M. Jozef RYCHLY H Directeur de Recherche, Sandia National Laboratories, Albuquerque Rapporteur M. Mathiew CELINA È Directrice de Recherche, Manchester Metropolitan University Examinateur Mme. Michele EDGE Professeur, PIMM, Arts et Métiers ParisTech Examinateur M. Xavier COLIN S Maître de Conférences HDR, PIMM, Arts et Métiers ParisTech Examinateur M. Emmanuel RICHAUD E Ingénieur R&D, Référent Vieillissement Matériaux, DETC-A, Renault Examinateur M. Eric DESNOUX Arts et Métiers ParisTech - Centre de Paris Laboratoire de Procédés et Ingénierie en Mécanique et Matériaux

ACKNOWLEDGMENTS

First, I would like to acknowledge Dr. Jozef RYCHLY and Dr. Matthiew CELINA for having accepted to be referees and thus, to carefully check my PhD manuscript. Dr. Michele EDGE and Pr. Jean-Luc GARDETTE are also greatly acknowledged as assessors for their deep examination of this work. Their remarks were very complementary and thus enabled to discuss many challenging issues and perspectives of the thesis and its approach in general.

Thereafter, I would like to thank my supervisors for having given me this PhD opportunity which turned out to provide both very comfortable working conditions and a very challenging and multidisciplinary topic. More particularly, I would like to express my gratefulness to Pr.

Xavier COLIN for our trustful relationship, its very constructive criticism and for having lent your continuous support to my project of article-based manuscript. I also thank Dr. Emmanuel RICHAUD for its warm welcome in the laboratory, its supervision as predecessor in the line of scientist oriented on polypropylene aging and its assistance in experiments (especially for Gel Permeation Chromatography experiments). I am also very gratefully to Mr. Eric DESNOUX as industrial supervisor and project leader for its very concerned project monitoring. I have really appreciated its efforts for making me acquainted with the industrial concerns without encroaching on time dedicated on PhD topic. It has enabled to meet as much as possible the theoretical academic aspects with the value-oriented requirements of industry.

Then, I would like to gratefully acknowledge the scientists and technicians whose mentioned

contributions have made this work possible:

Dr. Narcisse SIAMPIRINGUE, from the Centre National d’Evaluation et de Photoprotection (CNEP, Clermont-Ferrand), for UV-light exposure and careful control of irradiation conditions.

- Pr. Helene MESDAGH, Dr. Michel HENINGER and Mr. Julien LEPROVOST from University of Orsay/Alyxan, for real-time analysis of VOCs emissions.

- Dr. Alain GUINAULT from PIMM (CNAM), for his contribution and expertise in permeability measurements.

- Mr. Paulo FERRERA and Mrs. Anne GRANDMONTAGNE for their assistance in processing specimens.

- Mrs. Audrey PIERRE, Sonia ACHARD and Mr. Frederic RATEAU from Renault, Microscopy and Chemical Analysis Department, for STEM and NMR measurements.

- Mr. Christian FOURCADE, from Renault, Numerical Methods Department, for his assistance in getting acquainted with Open Modelica software for the numerical solving of systems of differential-algebraic equations, and obviously to Pr. Jacques VERDU for the tremendous scientific heritage he has handed down to the polymer aging team.

Afterwards, I would like to thank my colleagues from my teams at the Material Department of Renault, with a specific dedication to those of my previous modeling team “IPOM Forever” who helped me to keep confidence -sometimes faith- in benefits of numerical simulation but also for the very amicable work environment. Many thanks to Eric, Véronique, Lucas, Cécile, Emmanuelle, Alain, Camille and Alessandra! Similarly, I would like to show my thankfulness to my colleagues of the PIMM laboratory for the very friendly atmosphere which has always made me enjoying going at work, in particular Sophie, Camilo, Fidèle, Fatma, Paulo, Virginie, Denis, Magali, Julie, Yahya, Ines, Wissam, Amin, Octavie, Sebastian, Nidal, Adrien, Esteve and not forgetting my friend Nicolas. I cannot help to dedicate special thanks to my office colleagues, now friends, first my great friend Mouna and more recently Emilie, for having shared the inescapable timing of stress along PhD studies –and maybe for having endured my talkativeness ;-).

I will finish by expressing my deepest gratitude to my old friend Josephine for our indestructible bond of friendship, to my family for lending unconditional support. More specifically, I express my eternal recognition to to my parents who have urged me to embark on a scientific career up to the PhD and, above all, who have never desisted in doing their utmost for me.





CONTENTS

CONTENTS

GENERAL INTRODUCTION

1. CONTEXT

2. OBJECTIVES

3. STRUCTURE OF THE DISSERTATION

4. INTRODUCTION GENERALE [TRANSLATION IN FRENCH]

CHAPTER I. OVERVIEW OF THE LITERATURE

RESUME [SUMMARY IN FRENCH]

INTRODUCTION

1. MACROMOLECULAR MECHANISMS OF OXIDATION

1.1. Initiation processes: multiplicity and predominance of species

1.2. Propagation and multiplicity of reactive sites

1.3. Termination

2. KINETIC TREATMENT

2.1. Formalism of the closed- loop scheme

2.2. Extension to the photothermal oxidation case

1.1. The heterogeneity of oxidation: a scale issue

CONCLUSION: GENERAL STRATEGY AND RESEARCH SURVEY

CHAPTER II. MATERIALS AND METHODS- METHODOLOGICAL ASPECTS

RESUME [SUMMARY IN FRENCH]

1. INTRODUCTION

2. METROLOGY: GENERAL CONSIDERATIONS IN AGING EXPERIMENTS

2.1. The criteria for oxidation monitoring

2.2. Estimation of uncertainties and “error” bars

3. MATERIAL PREPARATION AND CHARACTERIZATION

3.1. Isotactic polypropylene morphological features

3.2. Procedure of purification in Soxhlet

4. CONTROL OF THE EXPOSURE CONDITIONS IN PHOTOTHERMAL AGING

4.1. Design of the tests matrix: an incremental approach

4.2. Specification of irradiation devices

4.3. Irradiation and sources’ spectra

4.4. Control of the temperature: difficulty in monitoring fast aging kinetics

5. ERRORS IN NUMERICAL SIMULATIONS

PART 1/ THERMAL OXIDATION

THERMOOXYDATION DU POLYPROPYLENE [SUMMARY IN FRENCH]

1. UNIVERSALITE ET AUTO-COHERENCE DU MODELE

1.1. Dépendance à la pression partielle en O2 (échelle locale)

1.2. Modélisation multi-échelles du système

1.3. Simulation de la variabilité des comportements

1.4. Domaine de validité et pouvoir prédictif

2. ALTERATION DES PROPRIETES AU COURS DU VIEILLISSEMENT ET CONSEQUENCES EN MODELISATION

CHAPTER III. REAL-TIME QUANTITATIVE ANALYSIS OF VOLATILE PRODUCTS GENERATED DURING SOLIDSTATE POLYPROPYLENE THERMAL OXIDATION

Abstract

1. INTRODUCTION

2. EXPERIMENTAL SECTION

2.1. Materials

2.2. Analysis

2.3. PTR-FTICR: apparatus & methods

3. RESULTS AND DISCUSSION

3.1. Real-time analysis: identification and quantification of VOCs

3.2. Effects of oxygen pressure

3.3. Mechanistic discussion

4. CONCLUSION

CHAPTER IV. ON THE IMPACT OF OXYGEN TRANSPORT PROPERTIES ON POLYPROPYLENE THERMAL

OXIDATION. PART I: EFFECT OF OXYGEN SOLUBILITY

ABSTRACT

1. INTRODUCTION

2. EXPERIMENTAL PART

2.1. Materials

2.2. Thermal aging conditions and FTIR aging monitoring

2.3. Characterization by complementary destructive analyses

2.4. Molecular weight measurements

2.5. Oxygen permeability

3. THEORY OF FORMAL KINETIC MODELING

3.1. Closed-Loop Mechanistic Scheme

3.2. Strategy for the optimization procedure

4. MODEL CALIBRATION WITH IPP1 IN OXYGEN DEFAULT

4.1. Determination of the oxygen transport properties

4.2. Modeling the changes in primary oxidation products

4.3. Modeling the build-up of secondary oxidation products

4.4. Modeling the changes in average molecular masses

5. DISCUSSION: TOWARDS A “UNIVERSAL” KINETIC MODEL

5.1. Common sources of variability in connection with initiation processes

5.2. Introduction of a variability on the coefficient of oxygen solubility

6. CONCLUSION

7. APPENDICES

7.1. Model equations, numerical computation and resolution

7.2. Analytical relationships for describing the oxygen pressure dependence of oxidation behavior.. 125

CHAPTER V. ON THE IMPACT OF OXYGEN TRANSPORT PROPERTIES ON THE KINETIC MODELING OF

POLYPROPYLENE THERMAL OXIDATION. PART II: EFFECT OF OXYGEN DIFFUSIVITY

ABSTRACT

1. INTRODUCTION

2. EXPERIMENTAL PART

2.1. Materials

2.2. Thermal aging and physico-chemical characterization

2.3. Oxygen permeability tests

3. KINETIC MODELING

4. RESULTS AND DISCUSSION

4.1. Variability of oxygen transport properties

4.2. Simulation of oxidation profiles - Impact of oxidation on oxygen transport properties................ 146 4.3. Impact of iPP thermal oxidation on the kinetic modeling

5. CONCLUSION

PART 2/ PHOTOTHERMAL OXIDATION

PHOTOOXYDATION DU POLYPROPYLÈNE [SUMMARY IN FRENCH]

1. INTRODUCTION

2. INTRODUCTION DE L’EFFET DE LA LUMIERE

2.1. Modèle analytique

2.2. Modèle numérique

3. LE CAS DE LA PIECE EPAISSE : COUPLAGE AVEC LE TRANSPORT DES REACTIFS MIGRANTS

CHAPTER VI. INFLUENCE OF TEMPERATURE, UV-LIGHT WAVELENGTH AND INTENSITY ON POLYPROPYLENE

PHOTOTHERMAL OXIDATION

ABSTRACT

1. INTRODUCTION

2. EXPERIMENTAL PART

2.1. Materials

2.2. Light and/or thermal exposure

2.3. Spectrophotometry measurements

3. RESULTS AND DISCUSSION

3.1. Impact of exposure conditions on lifetime

3.2. Cross sections of photosensitive species and calculation of the overlap function

3.3. Interpretation according to an empirical Schwarzschild’s law

3.4. Interpretation using a semi-empirical kinetic approach

4. CONCLUSION

5. APPENDIX A: THERMAL AGING RESULTS

CHAPTER VII. A GENERAL KINETIC MODEL FOR THE PHOTOTHERMAL OXIDATION OF POLYPROPYLENE.. 203

ABSTRACT

1. INTRODUCTION

2. EXPERIMENTAL PART

2.1. Materials

2.2. Photothermal aging

2.3. FTIR analyses

2.4. Hydroperoxides titration

2.5. Molecular weight measurement

2.6. Crystallinity ratios measurement

3. THEORY

3.1. Multi-Closed-Loop Mechanistic Scheme (MCLMS)

3.2. Kinetics in photochemistry

3.3. Model equations

4. EXPERIMENTAL RESULTS

4.1. Photothermal oxidation results

4.2. Comparison with pure thermal oxidation

4.3. Data scattering

5. KINETIC MODELING AND DISCUSSION

5.1. Optimization procedure - Numerical simulations and determination of unknown parameters... 232 5.2. Relative predominance of initiating species

5.3. Validity of the kinetic model

6. CONCLUSION

7. APPENDICES

7.1. Quantum yields from the literature

7.2. Spectral distributions of quantum yields

CHAPTER VIII. CHALLENGES IN THE NUMERICAL SIMULATION OF PHOTODEGRADATION PROFILES...... 255

ABSTRACT

1. INTRODUCTION

2. MODEL THEORY AND NUMERICAL RESOLUTION

2.1. Mechanistic scheme

2.2. Photochemical kinetics

2.3. Screening effect

2.4. Formalizing the problem

3. EXPERIMENTAL PART

3.1. Materials

3.2. Photothermal aging

3.3. Oxidation profiles

3.4. Measurements of opacity and reflectance

4. RESULTS AND DISCUSSION

4.1. Potentialities of the improved numerical tool for simulating photothermal oxidation profiles.... 274 4.2. Implementation for simulating experimental data

5. CONCLUSION

CHAPTER IX. GENERAL DISCUSSION

1. INTRODUCTION

2. ADVANCES IN THE KINETIC MODELING OF PHOTOTHERMAL OXIDATION

2.1. Towards a universal model for the thermal oxidation of iPP

2.2. Validity of the CLMS in photothermal oxidation

2.3. Attempts for extending the validity range of the photothermal oxidation model

3. LIMITATIONS OF THE KINETIC MODELING APPROACH

3.1. Implication of simplifying assumptions in formal and homogeneous kinetics

3.2. A complex multiphysical problem: insight from the case of thick specimens

3.3. Expectations from kinetic modeling

4. TOWARDS A KINETIC MODEL FOR PREDICTING THE LIFETIME OF TPO BLENDS

4.1. Describing the thermal oxidation of multiphase materials

4.2. Light attenuation issues in photothermal oxidation of TPO blends

5. DESIGNING AN UPGRADABLE TOOL FOR COMPLEX FORMULATIONS

5.1. Extension to complex formulations

5.2. Risks and challenges in numerical simulation of aging

5.3. Numerical issues

6. APPENDIX: A GENERAL FRAMEWORK FOR THE KINETIC TREATMENT OF PHOTOSENSITIZATION REACTIONS

GENERAL CONCLUSIONS

1. PHOTOTHERMAL OXIDATION MODEL

2. VALIDITY RANGE



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