Deradation behavior of compatibilized poly(butylene adipate-co-terephthalate)/thermoplastic starch blends

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University of New Brunswick
Nowadays, there is increasing research effort to develop bio-polymers for packaging from renewable sources. This development has caused a need to evaluate the properties of these polymers in different aspects. The current thesis work mainly focuses on the characterization of degradation behavior of poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch (TPS)/Talc composites. In the first part of this study, PBAT/TPS/Talc composites with potato starch in 20, 40, 50, and 60 wt% were prepared in a twin-screw extruder using modified PBAT (PBAT-g-GMA) as a compatibilizer. It was found that the mechanical properties of PGTPS composites were improved remarkably after the addition of talc. At a high strain rate, the tensile strength of all the samples increased significantly whereas the elongation at the break decreased. The second part of this study investigated the biodegradation of PGTPS composites in natural and controlled soil environment. For the biodegradation test in natural soil environment, the surface morphology, weight loss and mechanical properties of the composites were observed every month for 3 months. Results showed that the pure PBAT films almost did not lose weight, while the tensile strength and elongation at the break only changed slightly, which indicated that biodegradability of pure PBAT films was very limited. With increasing starch content in the blends, the tensile strength, and elongation at the break of PGTPS composites were reduced along with the increase of weight loss. More holes and cracks appeared on the surface of the PGTPS composites with prolonging the burial time. The biodegradation of PGTPS composites in controlled environment was evaluated by determining the CO2 released from the bioreactors for 72 days. Result showed that the presence of starch in composites promoted the biodegradation in terms of CO2 evolution. In the third part, the photo-degradation from the ultraviolet (UV) exposure was studied. The changes in the structure of the blends were determined using transform infrared spectroscopy (FT-IR). The main chain scission was found to be responsible for the UV degradation. The starch and talc components did not show any influence on the chemical structure of PGTPS composites in the UV degradation test.