CO2-derived microalgae as a biomass filler to fabricate green composite

Abstract

In this study, protein-rich microalgae (Chlorella sp. HS2) is investigated as a CO2-derived biomass particle to fabricate a sustainable green composite based on the physicochemical characterizations depending on the temperature and its dispersion and mechanical reinforcing effect in a polymer (poly(butylene adipate-co-terephthalate) (PBAT)) are investigated depending on temperature, incorporated with a small amount of reactive additives with peroxide or glycidyl functional groups. When HS2/PBAT is fabricated at a temperature higher than 130 °C, higher than that expected for thermal degradation of the protein in biomass, HS2 particles undergo cell disruption, changing the surface properties of the cells from hydrophilic to neutral and then reducing water absorption. This hydrophilic-neutral surface transition is attributed to the exposure of certain cell components, including proteins, lipids, and others such as amines, due to the disruption of the cells. It causes homogeneous dispersion of HS2 in PBAT during high mixing temperature. Despite the fact that HS2 is disrupted at high temperatures, the HS2 phase shows reactivity to reactive additives with peroxide or glycidyl functional groups, inducing interfacial bonding between PBAT and HS2 cells and enabling the composite to resist stretching deformation, resulting in increased tensile strength, particularly for composite films. This study demonstrates the potential of microalgae cells as a type of sustainability-reinforced biomass filler to fabricate a green composite. Different from natural biomass, microalgae HS2 cells, consisting of complex organic compounds, are disrupted at high mixing temperature and merged as a secondary phase in the polymer matrix. The addition of the CO2-derived microalgal biomass in synthetic polymer serves as the secondary phase and enhances sustainability, CO2 reduction, and cost-effectiveness without a significant sacrifice of mechanical performance.