Effects of chitin nanocrystals on coverage of coating layers and water retention of coating color

This study assessed the applicability of chitin nanocrystals prepared by 2, 2, 6, 6-Tetramethyl-1-Piperidine-1-oxyl radical (TEMPO)-mediated oxidation in traditional papermaking coating color systems. The α-chitin nanocrystals (CTNCs) with different carboxyl content, size, and morphology were prepared from crab shells by alkali pretreatment and TEMPO-mediated oxidation in the water at pH 10, and then the ratio of CTNCs to latex was applied to traditional coating color system to replace part of latex. The results showed that when the amount of NaClO added as co-oxidant in the oxidation was 15.0 mmol/g of chitin, the carboxyl content of alkali-pretreated CTNCs was up to 0.76 mmol/g. The amount of carboxyl groups presented a linear relation with the degree of individualization of nanocrystals and dispersion. When the ratio of latex to CTNCs was 90꞉10, the water retention value of the coating was 92% lower than that of the pure latex system, and the rheological property was better. The relationship between the addition amount of CTNCs and the surface strength and the coverage of coating layers were also studied, and results showed that when the ratio of latex to CTNCs was 95꞉5, the surface strength was the highest of 1.45 m/s, and the coverage of coating layers rate reached the highest of 78%.