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This work embraces two different manufacturing processes: pultrusion androtational moulding. One (pultrusion) is concerned with manufacture with athermosetting composite while the other is concerned with manufacture of anunfilled thermoplastic. The connecting theme is one of energy usage in manufacturewith these processes. While a large number of comprehensive computer models of pultrusion havebeen generated, most are focussed on the prediction of the temperature andconversion distributions within the profile; by contrast, the analysis presented here isdirected towards the prediction of the duty cycle of the mould heaters as a first stepin recognising the significance of the energy consumed in the process. The results ofthe model are compared with experimental measurements of the duty cycle of anindustrial machine. The nature of this particular investigation was predominantlyapplied and in particular directed towards industrial use. For this reason, the modelwas created in MATLAB, a software package which is relatively more accessible tothe reinforced plastics industry than FE packages. The project involved extensivemodelling and experimentation. It is shown that the line speed could be increased significantly by preheatingthe profile before it enters the die. For example, line speed for one particular profilewas increased from 0.4m/min to 0.5 m/min by using a pre-heater set at 80°C. Thiswork also showed that the specific energy consumption of the process was 0.2kWh/kg to 0.3 kWh/kg; under different line speeds and operating conditions. Thiswas achieved by measuring the duty cycle of the heaters on the die. This increase inline speed means a saving of up to 30 % of the specific energy consumption in thepultrusion. The energy theme continues through the work on rotational moulding. It isshown that the specific energy consumption in rotational moulding can be reducedby up to 70% by direct heating of the mould by using electrical resistance heatersinstead of current method of using hot air to heat the mould. The finite elementmodel showed that this alternative heating method is capable of producing asuniform a heat distribution on the surface of the mould as the current heating systemby using cyclic heating.

Le rotomoulage est une technique de transformation des polymères thermoplastiques qui souffre encore aujourd'hui d'un certain empirisme. Depuis de nombreuses années, la simulation du procédé de rotomoulage est considérée comme une nécessité à l'introduction de nouveaux matériaux et à l'élargissement de ses domaines applications. Ces travaux s'inscrivent à la suite de nombreuses études visant à développer un logiciel de simulation permettant de prédire le comportement de la matière en condition de mise en œuvre.L'objectif de cette thèse est de s'intéresser plus particulièrement à la simulation de la phase de refroidissement. Pour cela, il est nécessaire de mettre au point un modèle décrivant la cinétique de cristallisation et pouvant tenir compte des contraintes liées aux conditions thermiques extrêmes dans lequel se déroule le procédé (température, présence d'oxygène, temps de cycle long), lesquelles peuvent avoir une influence sur la thermostabilité du polymère. Dans le cadre de cette étude, le choix s'est porté sur le Polylactide (PLA). Le PLA présente une faible stabilité thermique et une cinétique de cristallisation lente, ce qui facilite l'observation de ces deux phénomènes. Dans un premier temps, la thermodégradation du PLA a été étudiée et un modèle visant à décrire son évolution dans des conditions proches de celles du procédé, a été mis en place. Puis, une étude de cristallisation considérant l'influence de la masse moléculaire et du polymorphisme du PLA, a été réalisée afin de modéliser sa cinétique. Enfin, un couplage des deux modèles a été envisagé dans l'optique de les intégrer à une simulation globale des transferts thermiques impliqués dans le procédé de rotomoulage. / Rotational molding is a thermoplastic polymer processing technology which has been, for many years, suffering from a kind of empiricism.The simulation of rotational molding is believed to be the key to introduce new materials and more diversity in its applications. This work follows several studies aimed to develop a simulation software which would predict the material behavior in processing conditions.Consequently, this thesis will focus specifically on the simulation of the cooling phase. This type of simulation requires kinetic crystallization modeling, acknowledging the influence that the extreme thermal conditions of the rotomolding process can have on the thermal stability of the material. In this study we chose to work with Polylactic acid (PLA), a material suffering poor thermal stability and presenting with slow kinetic crystallization, making it suitable to observe these phenomenona. First, the thermal degradation of PLA has been studied and a model describing its behavior, under similar conditions to processing, has been proposed. Then, a crystallization study including the influence of the molecular weight, as well as the polymorphism of PLA, has been completed and the kinetic crystallization modeling has been performed. Finally, the integration of both models in a global simulation of the thermal transfers describing the rotomolding process has been investigated.

A formulation of a subspace identification method for multi-phase processes with applications to rotational moulding and suggestions for improvements and experimental applications. / This thesis focuses on the implementation of subspace identification (SSID) for nonlinear, chemical batch processes by introducing a model identification method for multi-phase processes. In this thesis, a multi-phase process refers to chemical or biological batch-like processes with properties that cause a change in the dynamics during the evolution of the process. This can occur, for example, when a process undergoes a change of state upon reaching a melting point. Existing SSID techniques are not designed to utilize any known, multiphase nature of a process in the model identification stage. The proposed approach, Multiphase Subspace Identification (MPSSID), is conducted by first splitting historical data into phases during the identification step and then building a subspace model for each phase. The phases are then connected via a partial least squares (PLS) model that transforms the states from one phase to the next. This approach makes use of existing SSID techniques that allow for model construction using batches of nonunifrom length. Here, MPSSID is applied to a uniaxial rotational moulding process. In rotational moulding, the dynamics switch as the process undergoes heating, melting, and sintering stages that are visibly distinct and recognizable upon a certain temperature (not time) being reached. Results demonstrate the ability of multiphase models to better predict the temperature trajectories and final product quality of validation batches. As an extension to this rotational moulding analysis, additional MPSSID methods of implementation are proposed and the results are compared. A MPSSID mixed integer linear program is then introduced for implementation within model predictive control. The applications to rotational moulding are presented within the context of plastics manufacturing and the impact of plastic on the global climate crisis, with suggestions for future work. / Thesis / Master of Applied Science (MASc) / The control of chemical processes is an important factor in achieving high quality products. To control a process well, the mathematical model of the system must be accurate. In the past, mathematical models for process control were designed based on engineering approximations. Now, with major advances in computing and sensor technology, it is possible to design a simulation of the entire process. These simulations can be designed using first-principles or black box approaches. First-principles approaches utilize rigorous models that are based on the complex chemical and physical formulas that govern a system. Black box approaches do not look at the first-principles dynamics. They only utilize the measured process inputs and outputs to form a model of the system. They are widely used because of their ease of implementation in comparison to first-principles approaches. In this thesis, a new black box process control model is proposed and is found to yield better theoretical results than existing techniques. This model is tested on data from a plastics manufacturing process called rotational moulding, which involves loading polymer powders into a mould that is simultaneously rotated and heated to yield seamless plastic parts. Lastly, a control framework that is compatible with the new black box model is proposed to be used for future experimental tests.

Le développement de structures de plus en plus légères et présentant des rapports performances/coût toujours plus élevés est un enjeu permanent dans le domaine des transports. Les matériaux polymères présentent des caractéristiques particulièrement bien adaptées à ces besoins. Ce travail de thèse repose sur le développement d’un matériau polymère destiné à être utilisé en tant que liner de réservoir de stockage d’oxygène liquide (LOX). L’objectif est de démontrer une réduction des masses de l’ordre de 20 à 30%, en comparaison avec des structures métalliques. Pour les besoins de l’application, le matériau à développer se doit de présenter une bonne compatibilité au LOX, une faible perméabilité aux gaz, des propriétés mécaniques suffisamment élevées à basse température ainsi qu’une bonne aptitude à la mise en forme par rotomoulage. La première partie de ces travaux a porté sur la compatibilité au LOX des polymères. En tenant compte des théories proposées dans la littérature, des nanocomposites à matrice polyamide 6 (PA6) ont été élaborés et caractérisés afin d’atteindre les performances recherchées. L’influence de différents paramètres supposés régir la tenue à l’oxygène liquide des matériaux polymères a ensuite été déterminée. Les nanocomposites obtenus présentent globalement une bonne compatibilité avec le LOX. Cette étude a également permis de mettre en évidence que les résultats sont fortement dépendants des paramètres liés à l’échantillonnage. Dans un second temps, la processabilité par rotomoulage de ces nanocomposites PA6 a été évaluée. Les propriétés rhéologiques et de stabilité thermique ont notamment été étudiées. Quelques essais de rotomoulage sur les systèmes les plus pertinents ont également été réalisés et ont démontré des résultats encourageants. Dans une dernière partie, les propriétés barrière aux gaz de ces systèmes PA6 ont été étudiées. Les perméabilités mesurées ont été interprétées en tenant compte de la morphologie des mélanges. En particulier, cette étude montre que les nanocomposites à base de PA6 et de graphite lamellaire présentent des performances adaptées pour l’application en raison de l’effet de tortuosité induit par la charge. Les propriétés mécaniques en traction uniaxiale des systèmes élaborés ont finalement été déterminées et confrontées aux spécifications requises. Les résultats obtenus montrent que les caractéristiques mécaniques sont tout à fait adaptées pour une utilisation en tant que liner de réservoir de stockage d’oxygène liquide. / In the field of transport, the development of lighter, cheaper and more efficient structures is a recurrent challenge. Polymer materials are good candidates for these applications due to their characteristics quite suitable for requirements. This Phd work aims at developing a thermoplastic material which will be used as an internal liner of a liquid oxygen (LOX) storage tank. The objective is to demonstrate a 20 % to 30 % weight saving, compared to metallic structures. To be used in this kind of application, the thermoplastic material must be LOX compatible, processable by rotational moulding and display a low gas permeability as well as good mechanical properties at low temperatures. In a first part, LOX compatibility of polymers was studied. Taking into account theories proposed in the literature, polyamide 6 (PA6) nanocomposites based on LCP, fluoride and graphite fillers were processed and characterized in order to reach desired properties. The influence of several parameters having an impact on LOX behaviour of polymers was then investigated. The nanocomposites show overall good compatibility with liquid oxygen. This study also demonstrates that LOX sensitivity largely depends on the preparation of samples. The processability of nanocomposites by rotational moulding has then been investigated. Rheological properties and thermal stability have especially been studied. Some rotational moulding trials were carried out on the most relevant systems and demonstrate promising results. Finally, the gas transport properties of PA6 nanocomposites were studied. Measured gas permeability was discussed as a function of the morphology of blends. In particular, this study shows that PA6 nanocomposites filled with lamellar graphite present convenient performances which are due to the tortuosity effect induced by the filler. Mechanical properties of filled systems were finally determined and compared with set requirements. The results show that mechanical characteristics are quite relevant for use as internal liner of LOX storage tank.