Multifunctional and hybrid nanocomposites from micro/nano-fibrillated cellulose
- Autores: Pruthvi Kumar Bangalore Sridhara
- Directores de la Tesis: Fabiola Vilaseca Morera (dir. tes.)
- Lectura: En la Universitat de Girona ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Rafael Antonio Balart Gimeno (presid.), Xavier Espinach (secret.), Jordi J. Bou Serra (voc.)
- Programa de doctorado: Programa de Doctorado en Tecnología por la Universidad de Girona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
As a renewable alternative to petroleum-based materials, wood or plant-based materials offer a greater prospect in the transition towards sustainable replacements. Native to wood, cellulose nanofibers (CNF) form the major load bearing component and possess tremendous potential as a reinforcement material in polymeric matrices. This study focuses on nanocellulose-based composites and aims to prepare and characterize bio-(nano)composites with high cellulose weight/volume fraction. The influence of nanoscale reinforcement or nanostructure on the macroscopic properties of the nanocomposites are investigated. Distinct prominence is given to the effect of nanocellulose dispersion and nanocellulose/polymer interface on the physical characteristics of biocomposites.
In an initial study, effects of cellulose pulp fibers (micro scale dimensions) were investigated in pulp-fiber/polyamide 6 (PA6) composites system obtained by melt compounding and injection moulding. Strong influence on the pulp fiber reinforcement on the polymer matrix were observed with well dispersed pulp-fibers resulting in enhanced mechanical properties. Further, the effect of pulp fiber orientation within the composites was assessed and the composites with longitudinal fiber alignment recorded the highest mechanical properties.
Regarding the investigation of PA6 and cellulose nanofibers, two different approaches were used to process the nanocomposites. Firstly, solvent casting-based approach, where CNF derived from enzymatic pretreatment were used to produce high content of CNF biocomposites by adopting a green solvent mixture to disperse the CNF and then impregnated by the dissolved polymer. Nanocomposite formulations up to 50 wt% of CNF were prepared and characterized. Unique characteristics due to the nanostructure of composites are discussed corresponding to CNF dispersion, CNF network, and CNF/matrix interface. In addition, a comparison between the reinforcement effect of pulp-fiber and CNF are discussed to emphasize the importance of nano-scale reinforcement and their contribution in enhancing the physical properties of thermoplastic-matrix composites. Subsequently, melt processing approach with a high speed thermo-kinetic mixer was used to prepare PA6/CNF nanocomposites with up to 25 wt% formulations. This study focused on the industrial scalability and provided a methodology to produce high cellulose content CNF-nanocomposites at a commercial spectrum. Mechanical properties were characterized at different relative humidity and the investigation revealed good hygro-mechanical properties. All in all, the current nanocomposites exhibited excellent dispersion without major agglomerations and the mechanical properties were significantly enhanced with the addition of CNF in both the approaches.
Nanocomposites from polyamide-6 and high content of cellulose nanofibers were successfully prepared in this work, with remarkable improvement in the mechanical performance compared to the neat matrix, for both Young’s modulus and tensile strength. This in itself is an outstanding achievement, as compared to the literature up today. Moreover, the used methodology stands for industrial scalability and feasible processes towards the use of renewable and more sustainable products.
