Starch-based bioplastic with controlled physical properties and marine decomposition

In response to escalating marine plastic pollution, the development of biodegradable and bio-based polymers has gained interest lately. Many materials, including cellulose acetate, starch blends, and coated paper products, are described as biodegradable yet exhibit limited degradation in marine environments. In this study, starch-based bioplastic films were prepared via periodate oxidation of native tapioca starch (NTS) incorporated with glycerol (G) plasticization, and their structure-property degradation relationships were analytically studied. The aldehyde content was quantified by hydroxylamine titration and confirmed by spectroscopic analysis, with aldehyde content increasing systematically with oxidation degree. Moderate oxidation levels improved film ductility and toughness, whereas the excessive oxidation reduced mechanical integrity due to chain scission and overly rigid network formation. Moreover, oxidation-induced amorphization and modified intermolecular interactions were reflected in the changes in morphology, thermal stability, and surface wettability. Water interaction behavior was strongly environment-dependent. While films swelled gradually in deionized water, oxidized starch films underwent rapid swelling and physical disintegration in artificial seawater. This was leading to the critical role of ionic strength and salinity in governing film stability. Furthermore, marine biodegradation was evaluated using the biochemical oxygen demand (BOD) in accordance with the Organization for Economic Cooperation and Development 306 test guideline. NTS/G film showed higher initial oxygen consumption due to readily metabolizable glycerol, whereas oxidized films had slower BOD responses. Post-degradation was analyzed to confirm the progressive structural transformation with multiple analytical techniques. These findings demonstrate that disintegration and biodegradation are different processes in marine environments and can be tailored through chemical modification.