Titre de la dissertation: Solid-state modification of aromatic polyesters with enhanced properties: Mechanochemical development from batch to continuous flow process.

Promoteur de thèse: Prof Jean-Marie Raquez

Co-promoteur de thèse: Mme Rosica Mincheva

Résumé de la dissertation: Over the past century, the world has seen an increase in the use of polymeric materials – typically blended with additives or other modifiers to achieve the desired properties. Indeed, such physical or chemical modifications can improve processing capabilities, reduce costs, or extend the life of the material but it is crucial to strike a balance between modification and initial properties of the material. In this respect, there is a growing interest in developing new post-synthetic modification techniques that can impart the desired functionalities to existing materials, such as thermally assisted mechano-chemical modification.In this context, this PhD thesis aims to develop and validate solid-state post-synthetic modification method (SSM) from batch to continuous processes to inherently modulate the properties of aromatic semi-crystalline polyesters: poly(butylene terephthalate) (PBT) largely exploited in engineering applications and poly(ethylene furanoate) (PEF) emerging as a 100% bio-based aromatic polyester for packaging applications. SSM represents an easy-to-use tool to specifically alter the amorphous part of semi-crystalline polymers, thus preserving their main mechanical properties relative to crystalline phase. The first step of this work was to optimize the technique by considering the influence of various catalysts on batch SSM conducted on PBT in the presence of a diol monomer through calorimetric investigations. Once the feasibility of batch reactions was demonstrated, a biobased monomer derived from sugar was used to investigate the impact of different key parameters, such as temperature, time, and pressure, on the batch process and molecular weight reconstruction. Then, reactive extrusion (REx) was used as a continuous process to counteract the issues relative to mass and heat transfer that may occur in batch processes. Finally, the benefits to use SSM on these aromatic polyesters were demonstrated by improving the fire behaviour of PBT and modulating the crystallinity of PEF.