Effect of degree of deacetylation of chitosan on its performance as surface application chemical for paper-based packaging

Chitosan is a biopolymer that has shown promising results for surface treatment of paper to enhance barrier and mechanical properties. Commercially, chitosan is available with a wide range of degree of deacetylation (DD). Herein, effect of DD on performance of chitosan in surface application of paper is investigated. Surface application of chitosan of different DD (77%, 84% and 94%) was done at a dose of 1.0 ± 0.2 g/m² on kraft paper and comparison in terms of strength, structural, surface and barrier properties of paper was performed. Different DD of chitosan was confirmed by FTIR analysis. Results showed that breaking length of paper maximally increased by 15.2%/26.6% in machine direction (MD)/cross direction (CD), respectively after surface application of 94% DD chitosan followed by 77% DD and 84% DD. The maximum increase in burst index, stretch in MD and TEA in both directions of paper was found after surface application of 94% DD chitosan. Results attained by 77% DD and 84% DD chitosan for improvement in burst index, stretch and tensile energy absorption of paper were also encouraging. Maximum increase in stiffness was observed in CD with application of 84% DD chitosan. Double fold of paper also increased the maximum after surface application of 84% DD chitosan. The best results of contact angle, surface energy, Cobb₆₀ and water vapor transmission rate were attained after surface application with 94% DD chitosan whereas the results attained by 77% DD and 84% DD chitosan for contact angle, surface energy, Cobb₆₀ were also encouraging.