Development of Bioplastics Derived from Biomass for their Possible Application in Packaging

Abstract

[ES] La acumulación de plásticos de un solo uso genera estragos a nivel ecológico y ambiental, debido a la baja degradabilidad de los plásticos convencionales. Con un enfoque de avanzar hacia una económica circular, este estudio propone el uso de pasto como punto de partida para la obtención de bioplásticos. Los bioplasticos se obtuvieron a partir de hidrolisis alcalina, ya que se promueve la micro- y nano- fibrilación de celulosa. Las condiciones ideales para la hidrolisis fueron 1 M NH3 y 24 h de hidrolisis, donde se obtuvieron películas rígidas y fuertes. Posteriormente, estos bioplásticos se mejoraron con la adición de ε-polilisina (PL), por sus propiedades antimicrobianas. La adición de PL mostro un efecto plastificante obteniendo películas con módulos de Young de ~700MPa y una resistencia a la tracción de 12 MPa. Las películas con 10% PL mostraron baja solubilidad en agua (20%). Sin embargo, bajo agitación y presencia de agua es posible una solubilización del 100%. Este comportamiento, permitiría el reprocesamiento de estos bioplásticos. En cuanto a las propiedades antimicrobianas, la incorporación de PL generó películas antibacterianas contra las bacterias patógenas Escherichia coli and Staphylococcus aureus. Estos bioplásticos muestran propiedades interesantes que permitirían su uso en aplicaciones comerciales, contribuyendo así a una economía circular.

[EN] Nowadays, the accumulation of single-use plastics used in packaging is a main concern due to negative environmental impact. In a strive to move towards a circular economy, this study proposes grass as an interesting biomass to obtain new bioplastics. These bioplastics were obtained through alkaline hydrolysis that promotes the micro- and nano-fibrillation of cellulose followed by solution casting. In the first part of this thesis, the optimization of the grass hydrolysis was conducted by studying different hydrolysis times and alkaline media concentrations. The best hydrolysis conditions for this biomass were 1 M NH3 and 24 h of hydrolysis, as rigid and strong films were obtained. In a subsequent step, bioplastics were further improved by adding ε-polylysine (PL) as an antimicrobial compound. In terms of mechanical properties, the addition of PL showed a plasticizing effect with samples containing 10 and 20% PL being statistically the same in terms of rigidity with a Young’s Modulus of ~700MPa and a tensile strength of 12MPa. The grass bioplastic containing 10% PL showed low water solubility (20%). However, achieving 100% solubility is possible under mechanical stress in the presence of water. This behaviour suggests that the bioplastics could be easily reprocessed. Concerning the antimicrobial properties, the addition of PL allowed the obtaining of antibacterial films against Escherichia coli and Staphylococcus aureus. These biomaterials show interesting properties that could mean their use in real-world applications, contributing to the circular economy.