Tannery trimming waste based biodegradable bioplastic: Facile synthesis and characterization of properties

In the present research, the untanned proteinaceous trimming waste from tanneries was used to prepare highly flexible and transparent bioplastic films. Composite bioplastic films were fabricated by blending trimming hydrolysate powder and polyvinyl alcohol using the solution casting method. In addition, a non-toxic and relatively inexpensive bio-crosslinker – citric acid was used as a plasticizer/crosslinking agent. The effects of citric acid concentration on the mechanical properties, thermal stability, transparency and anti-microbial properties of the bioplastic films were investigated. Crosslinking interactions by the citric acid on the constituents of the bioplastic were confirmed using FTIR/ATR. Also, the surface microstructure of the films was studied using SEM. The resultant bioplastic films were smooth, uniform and defect-free. Citric acid used in the bioplastic blend formulation clearly acted as a plasticizer at higher concentrations. The trimming waste-based bioplastic with the citric acid concentration of 40% exhibited an outstanding tensile strength above 20 MPa and extremely high elongation at break value greater than 343%. The bioplastic degraded to an extent of 62% within 70 days under the soil burial test. The transparency of the bioplastics was comparable with the LDPE and PP-like conventional plastics. The anti-microbial properties of the films are the positive aspects brought about by the presence of citric acid interactions. Consequently, trimming based bioplastics may become a future friendly alternative to fossil derived plastics having applicability in packaging, wound healing and other biocompatible applications.