POLY(BUTYLENE SUCCINATE-CO-BUTYLENE ADIPATE)-BASED NANO-COMPOSITES: INSIGHTS INTO THERMOMECHANICAL PROPERTIES AND CRYSTALLIZATION KINETICS

This thesis investigates poly(butylene succinate-co-adipate) (PBSA)-based nanocomposites reinforced with spherical silica nanoparticles (SiO₂ NPs) and cellulose nanofibrils (CNFs). The main objectives of this work are: (i) assessing the impact of SiO₂ NPs and CNFs on PBSA crystallization kinetics and (ii) evaluating the thermo-mechanical properties, oxygen permeability, and compost disintegration behaviour of the nanocomposites. Notably, no compatibilizer was used in the formulations to allow for an examination of the intrinsic interfacial interactions between PBSA and the fillers. PBSA was chosen as the polymeric matrix due to its biodegradability in different environments and valuable mechanical properties, despite being relatively understudied compared to other biodegradable polymers. Due to their different morphology, the selected nanofillers were expected to offer different contributions to crystallization kinetics while ensuring that the biodegradability of PBSA was not compromised. Additionally, the inclusion of nanofillers in small concentrations (1%, 2%, and 5% by weight) was expected to significantly influence the thermal, mechanical and barrier to oxygen material properties. The formulations tested included neat PBSA and six nanocomposites with varying filler contents. Results indicated that SiO₂ NPs exhibited good dispersion with minimal flocculation and a strong interface with PBSA, whereas CNFs tended to form microscopic fibre clusters with poor interfacial adhesion. Crystallization studies revealed that SiO₂ NPs did not facilitate nucleation, while CNFs slightly enhanced crystallization, particularly in the glass-state regime. Thermal analysis showed that the addition of fillers did not alter the glass transition temperature (T_g), melting temperature (T_m), or crystallization temperature (T_c), though thermal stability improved. Moreover, mechanical tests revealed a higher modulus and elongation at break in the reinforced materials, signalling enhanced load-bearing capacity and ductility when subjected to an external stress. Additionally, both fillers enhanced the oxygen barrier properties of PBSA, with optimal improvements observed in formulations containing 1% SiO₂ NPs and 2% CNFs, and accelerated disintegration in composting conditions. While this study did not target a specific application, the findings suggest that these PBSA nanocomposites could be of interest for packaging applications, particularly in food-related contexts. Future research should explore the use of compatibilizers to improve filler dispersion and interfacial adhesion, as well as the potential for alternative filler morphologies to further enhance mechanical and gas barrier properties and to investigate their effect on the crystallization process and its kinetics.