Characterization and disintegration performance of thermoplastic starch-based film incorporated with aloe vera gel and polyethylene / Siti Fatma Abd Karim

Thirty years ago, researchers blended thermoplastic starch (TPS) and polyethylene (PE) to enhance the tensile strength of TPS and improve PE's disintegration ability to reduce plastic waste accumulation. Despite toxic compatibilizer/crosslinker addition to improve TPS/PE compatibility, TPS/PE compatibility was uncertain due to inconsistent tensile strength. Plus, the PE ratio in the TPS/PE blend was high, contributing to insignificant disintegration performance. Therefore, the incorporation of aloe vera (AV) to replace toxic compatibilizer while acting as a crosslinker into TPS to reduce the amount of PE used in TPS/PE film was investigated. The effects of AV and PE on TPS characteristics and disintegration performance were evaluated. Melt-blending and hotpress techniques were applied to produce TPS + AV + PE film, while the ISO 20200 technique was implemented to assess the disintegration performance. The formulation yielding the best tensile strength was TPS + 30% AV + 10% PE, with an average of 9.64 MPa due to the crosslinking effect that occurred between TPS and 30% AV gel and grafting formation between TPS + 30 % AV with 10% PE. The increment in melting and decomposition temperatures of TPS + 30% AV film verified the crosslinking performance between TPS and 30% AV. At the same time, the grafting of 10% PE on TPS + 30% AV film is supported by a decrement in water solubility percentage. The film's thickness, visual appearance, functional group changes, and crystallinity were also assessed. The TPS + 30% AV + 10% PE was considered biodegradable since 99% of the film disintegrated in the synthetic solid waste based on ISO 20200. The Hill model was chosen as the most suitable kinetics model to represent the disintegration behavior of TPS + 30% AV + 10% PE with the highest R2, lowest RMSE, and accuracy factor (AF) greater than one and closer to 1. Three phases of the disintegration process were proposed: fragmentation, hydrolysis, bioassimilation, and mineralization. The increment in weight loss percentage, void formation, and TPS functional compound disappearance suggested the proposed disintegration process. The increment in water contact angle percentage validated the disintegration mechanism. In conclusion, this study revealed the benefits of 30% AV gel and 10% PE in enhancing the TPS film. The disintegration ability of TPS + 30% AV + 10% PE within 90 days based on ISO 20200 suggests its high potential to be used as a commercialized biodegradable film packaging with a suitable application.