Electrical, optical and mechanical properties of chitosan biocomposites

In this work, chitosan/graphene nanoplatelets (CS/GNP) and chitosan/multi-walled carbon nanotube (CS/MWCNT) biocomposite films were prepared using a simple, eco-friendly and low-cost method. The electrical, optical and mechanical properties of these composite films were investigated. The optical, mechanical and electrical properties of the biocomposites were significantly improved, which make them promising materials for food packaging, ultraviolet protection and biomedical applications. With the increase of carbon filler content (GNP or MWCNT) in CS biocomposites, the surface conductivity (sigma), the scattered light intensity (I (sc) ) and the tensile modulus (E) increased significantly. This behaviour in the electrical, optical and mechanical properties of the CS/carbon filler biocomposites was explained by percolation theory. The electrical percolation thresholds were determined as R (sigma) = 25.0 wt.% for CS/GNP and R (sigma) = 10.0 wt.% for CS/MWCNT biocomposites, while the optical percolation thresholds were found as R (op) =12.0 wt.% for CS/GNP and R (op) = 2.0 wt.% for CS/MWCNT biocomposites. Conversely, the mechanical percolation thresholds for both CS/GNP and CS/MWCNT biocomposites were found to be negligibly small (R (m) = 0.0 wt.%). The electrical (beta (sigma) ), optical (beta (op) ) and mechanical (beta (m) ) critical exponents were calculated for both CS/carbon filler biocomposites and found compatible with the applied percolation theory