resumo
Thin nanocomposite films of thermoplastic starch, chitosan and cellulose nanofibers (bacterial cellulose or nanofibrillated cellulose) were prepared for the first time by solvent casting of water based suspensions of the three polysaccharides. The role of the different bioploymers on the final properties (thermal stability, transparency, mechanical performance and antimicrobial activity) of the films was related with their intrinsic features, contents and synergic effects resulting from the establishment of interactions between them. Thermoplastic starch displays an important role on the thermal stability of the films because it is the most stable polysaccharide; however it has a negative impact on the mechanical performance and transparency of the films. The addition of chitosan improves considerably the transparency (up to 50 % transmittance for 50 % of chitosan, in respect to the amount of starch), mechanical performance and antimicrobial properties (at least 25 % of chitosan and no more than 10 % of cellulose nanofibers are required to observe bacteriostatic or bactericidal activity) but decrease their thermal stability. The incorporation of cellulose nanofibers had the strongest positive impact on the mechanical properties of the materials (increments of up to 15 and 30 MPa on the Young's modulus and Tensile strength, respectively, for films with 20 % of BC or NFC). Nonetheless, the impact in thermal stability and mechanical performance of the films, promoted by the addition of chitosan and cellulose nanofibres, respectively, was higher than the expected considering their percentage contents certainly because of the establishment of strong and complex interactions between the three polysaccharides.
palavras-chave
PLASTICIZED STARCH; MECHANICAL-PROPERTIES; CELLULOSIC FIBERS; COMPOSITES; ANTIBACTERIAL; BIOCOMPOSITES; CRYSTALLITES; BEHAVIOR; WATER
categoria
Materials Science; Polymer Science
autores
Tome, LC; Fernandes, SCM; Perez, DS; Sadocco, P; Silvestre, AJD; Neto, CP; Marrucho, IM; Freire, CSR
nossos autores
Armando Jorge Domingues Silvestre
Professor Catedrático
Carlos Pascoal Neto
Diretor do Raiz
Carmen Sofia da Rocha Freire Barros
Investigador Coordenador
Isabel Maria Delgado Jana Marrucho Ferreira
Professor Catedrático
Liliana C. Tomé
Estudante de doutoramentoProjectos
agradecimentos
FCT (Fundacao para a Ciencia e Tecno logia) is acknowledge for Liliana C. Tome PhD Grant (SFRH/BD/72830/2010) and for Susana C. M. Fernandes Postdoctoral Grant (SFRH/BPD/70119/2010), and for financial support through the Projects PTDC/QUI/68472/2006, PEst-OE/EQB/LA0004/2011 (ITQB) and Pest-C/CTM/LA0011/2011 (CICECO). Isabel M. Marrucho would like to acknowledge FCT/MCTES (Portugal) for a contract under Programa Ciencia 2007. The authors are also grateful to Ricardo J. B. Pinto (CICECO, University of Aveiro) for performing the SEM experiments.