Improvement of mechanical strength and water repellency of Hanji (traditional Korean paper) through acetylation in supercritical CO2

Abstract

This work proposes to utilize supercritical CO2 as a reaction medium for the acetylation of Hanji, a traditional Korean cellulose textile, to enhance its water repellency while retaining the other properties. We first examined the phase behavior of acetic anhydride and CO2 mixtures, then a series of experiments were performed and statistically analyzed to find optimal operating conditions. Good surface hydrophobicity was attained in the optimized process within 4 h, shorter than classical non-catalytic liquid and gaseous processes. Hanji's tensile strength was also enhanced in the proposed process by a factor of 1.1, while it was aggravated in classical liquid processes. Hanji samples were slightly discolored in the proposed method, but the degree of discoloration was below the perception level. These results suggest that the proposed method has great potential to be used for the functionalization of cellulose-based textiles with a wide range of industrial applications.