Characterization and mechanical properties of plant-based bioplastics produced from waste Sorghum bicolour (Guinea corn)

Synthetic plastics cause environmental harm and emit toxins when not properly disposed of, threatening animal and human health. Bioplastics are proposed as alternatives; however, their properties currently limit widespread adoption. This study investigated the physical and mechanical properties of bioplastics derived from Sorghum bicolour (guinea corn), aiming to understand how varying additive compositions used in bioplastic fabrication influence their characteristics. Seven bioplastic samples (S0-S6) were fabricated utilising the casting technique by varying the proportions of citric acid, ranging from 0% to 30%, glycerol, from 0% to 50%, and gelatin, from 0% to 30%. Scanning Electron Microscopy (SEM) showed that higher additive proportions led to surfaces with greater homogeneity. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of hydroxyl, alkyl, and carbonyl functional groups, indicating the existence of alcohol, ester, and aromatic compounds. X-ray Diffraction (XRD) patterns showed semicrystalline structures with variations that corresponded to different additive levels. Nanoindentation testing revealed that sample S4 exhibited the highest nanohardness (0.19725 GPa) and modulus (13.556 GPa), whereas sample S5 demonstrated the lowest values. Tribological assessments indicated that sample S0 had the highest friction and wear, while sample S3 had the lowest. The wear resistance of these bioplastics surpassed that of conventional plastics. This research demonstrates that bioplastics derived from agricultural waste, such as guinea corn starch, are environmentally sustainable alternatives to petroleum-based plastics.