Bacterial Cellulose- and Laponite-Reinforced Corn Starch Bioplastics for Sustainable Packaging

Growing environmental concerns associated with petroleum-based plastics have stimulated the development of renewable and biodegradable alternatives. In this study, corn-starch-based composite films were prepared with bacterial cellulose (BC), α-cellulose (α-C), or carboxylated cellulose nanofibers (CNC) in the presence of laponite and glycerol. The films were characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis, optical measurements at 600 nm, tensile testing, qualitative solvent-exposure tests, and thermally induced repair experiments. Among the films containing different cellulose types, the bacterial-cellulose-containing bioplastic (BC-BP) exhibited the highest tensile strength and Young's modulus, reaching 4.47 and 0.229 MPa, respectively. The carboxylated-cellulose-nanofiber-containing bioplastic (CNC-BP) showed the highest elongation at break (100%) and the lowest thickness-normalized optical attenuation (0.38 mm^-1), whereas the α-cellulose-containing bioplastic (α-C-BP) exhibited the highest maximum degradation-rate temperature (approximately 315 °C). Increasing the BC content from 0.25 to 1.0 g increased tensile strength from 3.17 ± 0.13 to 7.78 ± 0.31 MPa and Young's modulus from 0.260 ± 0.002 to 0.996 ± 0.009 MPa. This increase was accompanied by a reduction in elongation at break from 41 ± 1.6% to 16 ± 0.6%. The BC-BP films retained their visible integrity after exposure to selected organic solvents but underwent substantial changes under strongly acidic and alkaline conditions. Following thermally induced repair, the BC-BP film recovered approximately 55% of its tensile strength and 45% of its Young's modulus while retaining an elongation at break close to that of the original film. These results demonstrate that cellulose type and BC content can be used to adjust the measured thermal, optical, mechanical, and repair properties of starch-cellulose-Laponite films. Further structural, barrier, migration, and food-contact safety evaluations are required to establish their suitability for packaging applications.