| Abstract:The effects of bleaching time, NaOH and H2O2 dosages in high-consistency retention stage of triploid poplar P-RC APMP on the pulp physical and optical properties were investigated. The three parametes were optimized mainly based on the brightness and the bulk of the handsheets. Under the optimized process conditions, the influences of various substitution percentages of MgO for NaOH on physical and optical properties of the pulp were studied. The results showed that the optimized parameters were 90 min of bleaching time, 3.5% NaOH and 3.5% H2O2. Under the optimized process conditions, with the increase of the substitution percentage of MgO for NaOH in the high-consistency retention stage (from 0% to 60%), the optical properties of the handsheets were improved, but the physical strength properties were decreased. As the MgO substitution percentage was 40%, the resultant P-RC APMP pulp could have a 2.4 ISO units brightness gain, a higher bulk and light-scattering coefficient, while the tensile index and the tear index were decreased by 23.9% and 22.4%, respectively, compared to those without any MgO substitution. |
