Experimental investigation of physicochemical, thermal, mechanical and rheological properties of polylactide/rice straw hydrochar composite

This study introduces a novel concept of rice straw hydrochar incorporation at different loadings (5%, 10%, 15%, and 20%), produced from microwave-induced hydrothermal carbonization (HTC) of rice straw to polylactide (PLA) for production of polylactide/hydrochar (PLA/HC) composites. Higher storage modulus was found for PLA/HC composites than that of neat PLA, confirming the formation of a network structure between PLA and hydrochar. Further, the storage modulus is directly proportional to the amount of hydrochar loading added to the PLA matrix. SEM images suggest that the neat PLA displays a smooth and soft surface. At the same time, PLA/HC blends showed irregular voids and cracks due to the porous structure of hydrochar, allowing PLA to infiltrate through pores of the hydrochar. The tensile modulus of neat PLA was increased from 2.627 GPa for neat PLA to 4.376 GPa, 4.895 GPa, 5.217 GPa, and 6.182 GPa for PLA/HC composites of 5%, 10%, 15%, and 20% hydrochar loadings, respectively. The thermal degradation temperature of the PLA/HC composites was 335–360 °C, which is slightly less than that of neat PLA but still stable up to the range of process and applications of PLA (30–240 °C) without compromising thermal degradation.