L’acide polylactique (PLA) est l’un des polymères biosourcés qui suscite le plus d’intérêt, mais ses propriétés thermomécaniques nécessitent d’être améliorées. Pour ce faire, les méthodes les plus utilisées et étudiées sont de le mélanger avec d’autres polymères ou bien d’y ajouter des charges minérales nanométriques (nanoparticules), afin de constituer un nanocomposite à matrice PLA. C’est dans la combinaison de ces deux approches que s’inscrivent ces travaux de thèse, consacrés à l’élaboration et à la caractérisation des propriétés de nanocomposites à base d’un alliage de PLA et de polyamide 11 (PA11) 80/20 m/m. L’objectif de cette thèse est l’obtention d’un matériau biosourcé aux propriétés thermiques, mécaniques et de réaction au feu améliorées par le contrôle de sa morphologie et l’ajout de nanoparticules et de retardateurs de flamme (RF). Pour y parvenir, deux techniques de compatibilisation, destinées à améliorer l’adhésion interfaciale entre le PLA et le PA11, ont été évaluées. La première consistait à incorporer des nanoparticules de silice. Il a été noté d’importantes modifications de la morphologie et des propriétés rhéologiques du mélange d’étude, selon leur localisation dans le mélange étudié fonction de la nature chimique de la surface de la silice. La deuxième consistait à introduire un copolymère époxyde multifonctionnel réactif, dénommé Joncryl. La réactivité de ce copolymère avec le PLA et le PA11 a permis de compatibiliser le mélange d’étude, conduisant à une morphologie plus fine et à l’obtention de propriétés mécaniques supérieures à celles du mélange d’étude, en particulier avec l’ajout de 3%m de Joncryl. Des échantillons basés sur les mélanges compatibilisés par cette méthode ont été préparés par le procédé de fabrication additive FDM. Une étude de l’impact de ce procédé sur la morphologie et les propriétés mécaniques obtenues a été entreprise. Enfin, une meilleure réaction au feu pour le mélange compatibilisé avec 3%m de Joncryl a pu être obtenue par l’ajout combiné de nanoparticules de phyllosilicates et de RF. / Polylactic acid (PLA) is one of the biobased polymers that generates the most interest, but its thermomechanical properties need to be improved. To do that, the most used and studied methods consist of blending PLA with other polymers or adding nanoscaled mineral fillers (nanoparticles) to get a PLA based nanocomposite. This PhD work is dedicated to the elaboration and properties characterization of nanocomposites based on a filled PLA and polyamide 11 80/20 wt/wt blend. The aim is to obtain a biobased material with improved thermal, mechanical and fire reaction properties by controlling its morphology through the addition of nanoparticles and flame retardants additives.To achieve that, two compatibilization techniques, aiming to improve PLA-PA11 interfacial adhesion, were evaluated. The first one consisted of adding silica nanoparticles. Important changes of the blend morphology and rheological properties were noticed, depending on the localization of the two different silica nanoparticles used into the polymer blend phases. The second one consisted of introducing a reactive multifunctional epoxy copolymer, named Joncryl. The reactivity of this copolymer with PLA and PA11 allowed to compatibilize the blend, leading to a fine morphology and higher mechanical properties compared to those of the pristine blend. Samples of compatibilized blends obtained through this method were processed using FDM additive manufacturing process. A study of the influence of this process on the morphology and mechanical properties obtained for these samples was performed. Finally, a better fire reaction of compatibilized polymer blend with 3%wt Joncryl was obtained by the combined addition of phyllosilicates nanoparticles and flame retardants.

Stab resistant body armour had been used throughout history, with examples ranging from animal hide construction to the moulded Polycarbonate units typically used by United Kingdom (UK) Police Officers. Such protective articles have historically, and continue to present a number of issues which have shown to impair the operational performance of its wearer including but not exclusive to poor thermal regulation, large masses, and reduced manoeuvrability. A number of developments have been made in an attempt to minimise the effects of such issues. One potential solution yet to be fully explored is the utilisation of Additive Manufacturing (AM) technologies. In recent years the use of such manufacturing technologies, particularly Laser Sintering, has successfully demonstrated their suitability for a range of high performance applications ranging from Formula 1® to aerospace. Due to the fundamental additive nature of AM build processes, the utilisation of such technologies have facilitated the realisation of design concepts that are typically too expensive, difficult or impossible to create using traditional manufacturing processes. In order for AM technologies to be used for the generation of stab resistant body armour a number of historical issues and performance characteristics fundamental to ensure stab resistance is achieved must be satisfied. This body of research firstly evaluated the stab resistive performance of two of the most common materials suitable for Laser Sintering as highlighted by an initial review of AM technologies. Once an appropriate material had been highlighted it was used as the basis for further experimental testing. Such tests focussed on minimising the material thickness required to maintain an appropriate level of stab resistance within United Kingdom Home Office Scientific Development Branch (HOSDB) KR1-E1 requirement of 24 Joules of stab impact energy. Test results demonstrated that specimens manufactured from Duraform EX® required a minimum single layer thickness of 11.00 mm, and a dual layer total thickness of 9.00 mm to provide an appropriate level of stab protection within the HOSDB KR1-E1 standard. Coupled with the results generated from an investigation identifying the overlapping/imbricated assembly angle required to maintain an appropriate level of coverage across a scale structure, the stab resistant characteristics initially identified were used for the development of an imbricated scale-like assembly. Additional design features were also investigated to further minimise the total thickness of the final element design and corresponding assembled imbricated structure such features included angling strike surfaces and integrating a dual layered structure within individual elements. When the finalised imbricated assemblies were stab tested, they successfully demonstrated levels of stab resistance to the UK HOSDB KR1-E1 impact energy of 24 Joules.