Sodium periodate oxidation of cellulose nanocrystal and its application as a paper wet strength additive

The oxidation of cellulose nanocrystal (CNC) by sodium periodate can generate aldehyde functions for crosslinking reactions or for further modification, which can extend the range of applications of CNC. In this paper, the effects of reaction conditions during the periodate oxidation of CNC, such as oxidant concentration, pH, temperature and oxidation time on the oxidized CNC yield and the aldehyde content, were investigated and an optimized reaction condition was identified. The generation of aldehyde groups on the CNC was confirmed by Fourier transform infrared spectroscopy analysis, and the decreased crystalline index was observed by X-ray diffraction. The transmission electron microscope observation showed the morphological changes of CNC after the oxidation. The oxidized CNC was used as a strength additive to paper, and the results showed that the dry tensile index was 32.6 % higher than the control sample, and the wet tensile index was reached to 3.08 N.m/g, at the oxidized CNC dosage of 1.2 %.