Surface application of different concentrations of chitosan on recycled paper and its impact on packaging properties

The present study explored chitosan, a biodegradable nontoxic biopolymer, at different dosages for surface treatment of recycled paper to improve various properties relevant to packaging. Chitosan, at all applied concentrations, improved important paper properties like surface, strength and barrier due to which the low strength paper can also be used as a packaging paper. The effects of surface treatment of chitosan solutions of different concentrations on paper were analyzed by measuring breaking length, burst index, tear index, double fold, stiffness, air permeance, water vapor transmission rate (WVTR), wax pick, tensile energy absorption (TEA), and stretch. After surface treatment by 1% solution of chitosan, the breaking length, double fold, TEA, and stretch in machine direction were increased by 53.8%, 243%, 93%, and 75%, respectively, whereas burst index was increased by 38.4% in comparison with the base paper. The WVTR was reduced from 706 to 496 g/m 2 /24 h, and air passage time was increased from 18 to 65 Gurley s after surface treatment by 1% chitosan solution on the base paper. The chitosan solution at all the concentrations showed antibacterial activity in plate assay therefore reducing the susceptibility of paper to microbial attack. Graphical abstract