Influence of HNO3/H3PO4–NANO2 mediated oxidation on the structure and properties of cellulose fibers

The bamboo pulp cellulose fiber was oxidized with HNO3/H3PO4–NaNO2 mixture to obtain oxidized cellulose containing different levels of carboxyl content and with high yields. The effects of HNO3/H3PO4–NaNO2 mediated oxidation on structure and properties of the fiber were investigated. The results showed that an increase in carboxyl content and weight loss of oxidized fibers appeared with increasing oxidation time. Compared with the original cellulose, the oxidized fibers had lower crystallinity (29–40%) and thermal stability. The patterns of 13C NMR, X-ray diffraction and other testing methods revealed that the oxidation mostly occurred at C6 primary hydroxyl groups of cellulose. Moreover, an oxidized fiber with 94.14–98.59% of high yields and 1.13–3.56% of carboxyl content was obtained in the range of oxidation time from 15 to 60 min, while its mechanical properties did not change significantly. This work presented some detailed information about structure–property correlations of oxidized bamboo pulp cellulose fibers and was useful in planning applications of these products.