Arrowroot Starch/ZnO Nanoparticle Nanocomposite Films: Thermal, Morphological, and Tensile Properties

Petroleum-derived conventional plastics play an important role in our lives despite their accumulation in the environment. An alternative is natural polymers, in which starch has been highlighted. However, starch-derived films exhibit a low tensile strength. One way to improve this is by adding zinc oxide nanoparticles (ZnO NPs). In this work, thermoplastic arrowroot starch/ZnO nanocomposite (TPA/ZnO NC) films were manufactured by solvent casting, and their thermal, tensile, morphological, and soil burial degradation properties were investigated. In addition, the TPA/ZnO NC films were evaluated for their suitability for bread packaging. TEM confirmed the nanometer dimension for ZnO. XRD confirmed the formation of a thermoplastic material with characteristic peaks of ZnO NPs, but characteristic bands for ZnO were not observed in the FTIR. SEM images showed that ZnO NP concentrations are randomly distributed in the TPA matrix. The ZnO NPs did not cause major changes in the thermal degradation profile of the NC films in relation to the starch matrix, as demonstrated by TGA results. TPA and TPA/ZnO-5 films exhibited an improvement in tensile strength (0.62-1.44 MPa) and modulus (1.73-10.46 MPa), respectively. ZnO NPs modified the moisture, solubility, and transparency of the films. Our results demonstrate that soil burial degradation for the films depends on the soil moisture. Black and yellow spots, characteristic of fungal growth, were not observed on bread stored in the TPA/ZnO-3 and TPA/ZnO-5 films. Our results indicate that TPA/ZnO-5 demonstrated a favorable combination of σ, ε, and <i>E</i> and also exhibited soil burial degradation.