Improvement of biodegradable polymer film properties by incorporating functionalized few-layer graphene

Functionalized few-layer graphene (FFG) prepared employing an eco-friendly liquid exfoliation method using coffee waste extract was added to three biological and one synthetic polymers. Chitosan/FFG, polyvinyl alcohol (PVA)/FFG, sodium alginate/FFG, and gelatin/FFG composite films were developed using variable concentrations of FFG (0–1 wt% of polymer). The developed films were characterized for water content, swelling degree, thickness, thermal and mechanical properties, water vapor permeability, and indoor soil burial degradation. In comparison to the pure chitosan, PVA, sodium alginate, and gelatin films, the inclusion of FFG significantly increased the tensile strength up to 439%, 247%, 190%, and 195%, respectively. Moreover, the Young’s modulus of the developed composite films was improved up to 515%, 253%, 144%, and 341%, respectively. The elongation at break of chitosan and PVA films declined with FFG concentration, while the maximum elongation at break existed for sodium alginate/FFG and gelatin/FFG films. The water vapor permeability of chitosan, PVA, sodium alginate, and gelatin composite films decreased by 87%, 67%, 50%, and 55%, respectively, with the addition of only 1% FFG. The incorporation of FFG reduced both the water content and swelling degree of all composite films. In addition, the composite films showed similar degradation after addition of FFG in the 60-day soil burial test.