Abstract: Abstract: Cotton fabrics were selectively oxidized by HNO3/H3PO4-NaNO2 mediate system to obtain the monocarboxyl cellulose, and then chitosan bonded with monocarboxyl cotton fabric through the amide reaction in chitosan solution. Effects of oxidation time of HNO3/H3PO4-NaNO2 on carboxyl content, breaking strength of oxidized cotton fabrics and weight gain of cotton fabric grafted chitosan were studied and the maximum weight gain of 5.52% was obtained when the oxidation time was chosen as 45min. The analysis of CP/MAS 13C NMR, FT-IR, SEM and XRD demonstrated that the primary hydroxyl at C6 site in glucose units of cotton cellulose was selectively oxidized to carboxyl group by HNO3/H3PO4-NaNO2 system, subsequently the amido bond of C-N was formed between amino groups in chitosan and active carboxyl groups on oxidized cotton fabrics and chitosan covered on the surface of oxidized cotton fabrics by the covalent bond. After chitosan graft reaction, the crystallinity of monocarboxyl cotton fabric decreased from 65.37% to 60.86%, and the breaking strength, whiteness and capillary effect of chitosan grafted cotton fabrics slightly reduced, whereas the wrinkle recovery angle of modified fabrics significantly increased.

Key words: monocarboxyl cellulose, chitosan, cotton fabric, selective oxidation at C6 site, amide reaction