Upcycling tobacco extract residue into poly(butylene adipate-co-terephthalate) composites via gallic-acid compatibilization for circular agricultural use

This study investigates the use of tobacco extract residue (TER), an extraction byproduct, as a filler in poly(butylene adipate-co-terephthalate) (PBAT) composites. The composites containing 10, 20 and 40 wt% TER were prepared and systematically tested and characterized. Experimental results showed that increasing TER levels enhanced stiffness and crystallinity degree of the composites. However, the tensile strength and elongation at break were both decreased. These mechanical reductions were related to an insufficient interfacial adhesion between two components. Additionally, the higher TER contents also enhanced hydrophilicity and diffusion coefficients, leading to the increase of water absorption. To remedy these drawbacks, gallic acid (GA) was introduced as a compatibilizer at content ranging from 1 to 10 wt%. Its hydroxyl and carboxyl groups could create hydrogen bonding and possible covalent interactions with both PBAT and TER, as suggested by FTIR analysis. Microscopic observations revealed improved interfacial adhesion at all GA contents. GA acted as a bio-based interfacial modifier, offering a more sustainable alternative to conventional compatibilizers. Thermogravimetric analysis indicated that all compatibilized compositions enhanced thermal stability, compared to the composite without compatibilizer. Based on the experimental results, the composites containing 40 wt% TER and 1 wt% GA exhibited the balanced stiffness, toughness, thermal stability and raw materials cost reduction, which potentially approached for applying in biodegradable agricultural applications.