Coquillat, Marie (2007) Ageing of polybutadiene based propellants : kinetic modelling of oxidation. PhD thesis Mécanique et Matériaux, ENSAM 2007ENAM0021 p.186.
Full text available as:
|
|
Abstract
The goal of this thesis was the elaboration of a kinetic model for the lifetime prediction of polybutadiene matrix propellants. In the storage conditions, their ageing is dominated by radical chain oxidation of polybutadiene sequences. First, the thermooxidation of the linear prepolymer was studied. The classical physico-chemical determinations were made : double bond consumption, carbonyl, hydroxyl, epoxide and hydroperoxide build-up, but also molar mass determination using rheometry and global mass evolution using gravimetry. All these experimental data were used to build a mechanistic scheme from which a kinetic scheme was derived and solved numerically. It is used in inverse approach to determine certain elementary rate constants. Then, shear modulus measurements from dynamic torsion testing and gravimetry were realized on isocyanate crosslinked samples. The rubber elasticity theory was used to establish the relationship between modulus and number of chain scission or crosslinking events induced by oxidation. The modelling results allowed establishing that intramolecular radical additions to double bonds are considerably more frequent than intermolecular ones. Despite that, intermolecular additions are responsible for predominant crosslinking. The results of this part, integrated to the kinetic model (in which reaction-diffusion coupling was taken into account) allowed to predict the distribution of local modulus values in the sample thickness. Then, structure mechanics allowed calculating the overall mechanical response of a bulk part undergoing oxidative ageing. Finally, we studied the stabilization mechanisms and kinetics in the case of hindered phenol stabilizers. The experimental study showed that the phenol is mostly consumed by a direct reaction with oxygen. Polybutadiene differs, in this aspect, from polyolefins where this reaction plays a significant role only at high oxygen pressures (few MPa). It explains why polydienic rubbers need higher stabilizer concentrations than polyolefin for stabilizing performances of the same order or lower.
| Item Type: | PhD Thesis (PhD) |
|---|---|
| Thesis Supervisor: | Verdu, Jacques |
| Date: | 21 September 2007 |
| Board of examiners: | Lacoste, Jacques and Vallat, Marie-France and Stevenson, Isabelle |
| Ecole Doctorale: | ED 432 ECOLE DOCTORALE SCIENCES DES METIERS DE L'INGENIEUR |
| Discipline: | Mécanique et Matériaux |
| Collection (Fonds): | ENSAM |
| Institution: | ENSAM |
| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
| Uncontrolled Keywords: | Polybutadiène, Oxydation, Modélisation, Cinétique, Elasticité caoutchoutique, Mécanismes, Antioxydants, Diffusion, Polybutadiene, Oxidation, Modeling, Kinetics, Rubber elasticity, Mechanism, Antioxidants, Diffusion |
Table of content
Introduction génèrale - 5
I Synthèse Bibliographique - 7
1 Propergols - 9
2 Méthodes de prédiction de la durée de vie.19
II Matériaux & Méthodes expérimentales - 59
III Résultats & Discussion - 79
4 Oxydation du PBHT - 81
5 Oxydation du PBHT réticulé - 125
6 Oxydation du PBHT stabilisé - 153
IV Conclusions & Perspectives - 167
| ID Code: | 2967 |
|---|---|
| Deposited By: | Marie Coquillat |
| Deposited On: | 25 October 2007 |
Repository Staff Only: edit this item