Effect of calcium carbonate on the performance of poly(butylene adipate-co-terephthalate) filled with duckweed biomass

Blending poly(butylene adipate-co-terephthalate) (PBAT) and thermoplastic starch (TPS) results in a tough biodegradable plastic. TPS is always produced from edible crop-derived starch. An alternative source of starch and protein polymers, duckweed biomass has a relatively small impact on the human food chain. The present work studies the feasibility of using duckweed biomass as a replacement for cassava starch for TPS production and investigates the effect of calcium carbonate (CaCO3) on the performance of PBAT filled with duckweed biomass. PBAT/TPS and PBAT/duckweed masterbatch (DM) blends with a constant weight ratio of PBAT:TPS and PBAT:DM of 60:40 were prepared using a twin-screw extruder and then molded into dumbbell-shaped specimens using an injection molding machine. PBAT/DM/CaCO3 composites containing CaCO3 in the range of 10%− 30 wt% were also fabricated. Duckweed biomass has the potential to replace cassava starch in PBAT blends; however, the properties of those blends differ. The PBAT/DM blend exhibited higher density and melt flow index, but lower elongation at break, shore D hardness, and thermal stability than PBAT/TPS blend. In addition, DM facilitated the crystallization of PBAT during cooling. Adding CaCO3 could reinforce the PBAT/DM blend, enhancing its Young’s modulus and hardness while reducing tensile strength and elongation at break. Moreover, added CaCO3 improved the thermal stability but reduced the melt flow index of the PBAT/DM blend. The resulting PBAT/DM/CaCO3 composites are promising sustainable materials for biodegradable injection-molded products with an acceptable cost.