This work forms part of a project aimed to develop Polyamide 6,6(PA6,6)-based automotive fuel tanks. PA6,6 is a good candidate for technical applications since it possesses good thermo-mechanical properties compared to its weight. These formulations must exhibit good impermeable properties to classic gasoline, to biofuels (gasoline containing ethanol), and to water which is found in the atmosphere, while keeping good impact behavior.The scientific issues are the better understanding of PA6,6-solvent interactions in the case of a series of solvents having different sizes and polarities and also for a set of ternary mixtures composed of ethanol, toluene, and isooctane at various concentrations that model biofuels. The effect of these solvents on the glass transition temperature Tg (molecular mobility signature) was assessed. The effect of additivating or chemically-modifying PA6,6 on the impact and barrier properties of the polymer was studied.In this work, it was described how the nature of a solvent conditions its sorption and its plasticizing effect on PA6,6. It was also observed that the PA6,6 inter-chain interactions also condition the solvent sorption. Moreover, a thermodynamic approach describing the sorption and plasticizing effects of ternary mixtures in PA6,6 was considered and developed. It was also observed that PA6,6 mechanical properties depend or are related to the amorphous phase molecular mobility state.

Ce travail s’inscrit dans le projet de développement des réservoirs essence pour voitures à partir des formulations Polyamide 6,6 (PA6,6). Le PA6,6 est un bon candidat pour des applications techniques car il possède des bonnes propriétés thermomécaniques rapportés à son poids. Ces formulations doivent montrer des bonnes propriétés barrière aux essences classiques, aux biofuels (essence contenant de l’éthanol) et aussi à l’eau qui est présente dans l’atmosphère, tout en ayant une bonne tenue aux chocs.Les enjeux scientifiques sont la meilleure compréhension des interactions entre le PA6,6 et des solvants purs de polarités et tailles différentes mais aussi des mélanges ternaires composés d’éthanol, toluène et isooctane à différentes concentrations et qui modélisent les biofuels. On veut aussi étudier l’effet de ces solvants sur la température de transition vitreuse Tg qui est la signature de la mobilité moléculaire de la phase amorphe. Ensuite, l’effet de l’additivation ou de l’ajout des co-monomères sur les propriétés barrière et mécaniques, notamment les propriétés choc, a été étudié. Dans ce travail nous avons pu décrire comment la nature d’un solvant conditionne sa sorption et son effet plastifiant dans le PA6,6. On a aussi observé que la nature et les interactions interchaînes de la matrice polymère conditionnent aussi la prise en solvants. De plus, une approche thermodynamique a été proposée pour étudier et comprendre la sorption de mélanges ternaires éthanol-toluène-isooctane et leur effet plastifiant dans le PA6,6. On a aussi montré que les propriétés mécaniques du PA6,6 dépendent ou sont liées à l’état de mobilité moléculaire de la phase amorphe de ce polymère. / This work forms part of a project aimed to develop Polyamide 6,6(PA6,6)-based automotive fuel tanks. PA6,6 is a good candidate for technical applications since it possesses good thermo-mechanical properties compared to its weight. These formulations must exhibit good impermeable properties to classic gasoline, to biofuels (gasoline containing ethanol), and to water which is found in the atmosphere, while keeping good impact behavior.The scientific issues are the better understanding of PA6,6-solvent interactions in the case of a series of solvents having different sizes and polarities and also for a set of ternary mixtures composed of ethanol, toluene, and isooctane at various concentrations that model biofuels. The effect of these solvents on the glass transition temperature Tg (molecular mobility signature) was assessed. The effect of additivating or chemically-modifying PA6,6 on the impact and barrier properties of the polymer was studied.In this work, it was described how the nature of a solvent conditions its sorption and its plasticizing effect on PA6,6. It was also observed that the PA6,6 inter-chain interactions also condition the solvent sorption. Moreover, a thermodynamic approach describing the sorption and plasticizing effects of ternary mixtures in PA6,6 was considered and developed. It was also observed that PA6,6 mechanical properties depend or are related to the amorphous phase molecular mobility state.

Brittleness of a polymeric material has a direct relationship with the material's performance and furthermore shares an inverse relationship with that material's flexibility. The concept of flexibility of materials has been understood but merely explained with a hand-waving manner. Thus, it has never been defined by a calculation, thereby lacking the ability to determine a definite quantitative value for this characteristic. Herein, an equation is presented and proven which makes determining the value of flexibility possible. Such an equation could be used to predict a material's flexibility prior to testing it, thus saving money and valuable time for those in research and in industry. Substantiating evidence showing the relationship between flexibility of polymers and their respective mechanical properties is presented. Further relating the known tensile properties of a given polymer to its flexibility is expanded upon by proving its relationship to the linear coefficient of thermal expansion for each polymer. Additionally, determining flexibility for polymers whose chemical structures have been compromised by respective solvents has also been investigated to predict a solvent's impact on a polymer after exposure. Polymers examined through literature include polycarbonate (PC), polystyrene (PS), teflon (PTFE), styrene acrylonitrile (SAN), acrylonitrile butadiene styrene (ABS), poly(ethersulfone) (PES), low density polyethylene (LDPE), polypropylene (PP), poly(methyl methacrylate) (PMMA), and poly(vinylidene fluoride) (PVDF). Further testing and confirmation was made using PC, PS, ABS, LDPE, PP, and PMMA.