Fiber structures and properties of eucalyptus kraft pulp via different bleaching methods

The fiber morphology, the content of hydrogen bonds (HBs) of different models, cellulose crystalline structure, water retention value (WRV), and strength properties of eucalyptus pulp bleached by different bleaching methods (hydrogen peroxide bleaching and sodium dithionite bleaching) were investigated. The results of fourier transform infrared spectrometer (FTIR) showed that the content of intramolecular hydrogen bonds (HBintra) increased by 11.6 % and 4.8 % after hydrogen peroxide bleaching and sodium dithionite bleaching, respectively. The energy of the hydrogen bonds was changed after bleaching treatment. The hydrogen bonding distances showed a small change after different bleaching treatment. The results of X-ray diffraction (XRD) demonstrated a decrease in the average width of crystallite size in the (002) lattice plane after different bleaching treatment, which was the same trend with the variability of cellulose crystallinity. Compared with the unbleached pulp, the WRV and strength properties of the bleached pulp increased after each bleaching process. Tear index of handsheets made from the hydrogen peroxide and sodium dithionite bleaching pulps were 46.0 % and 54.8 %, respectively. The sodium dithionite bleaching treatment had more significant effects on fiber swelling capability.