TEMPO Mediated Oxidation Optimization on Thermomechanical Pulp for Paper Reinforcement and Nanomaterial Film Production

Abstract

The 4-acetamido-TEMPO mediated oxidation system is well known on pure cellulose, but further investigation on more complex cellulose sources, such as thermomechanical pulp that is also composed of hemicelluloses and lignin, is needed. The reaction on wood pulp allows improvement in paper strength and nanofibril material production. However, the effects of the reaction parameters are not known enough to scale up the oxidation. With the help of two experimental designs, the chemical amounts, reaction temperature and time, sodium hypochlorite injection time, and nanofibril dispersion time were all studied. During the experiments, it was possible to observe pulp bleaching or delignification. Increasing the 4-acetamido-TEMPO amount promoted the pulp oxidation. In contrast, a large excess of sodium bromide and sodium hypochlorite was advantageous for pulp bleaching and delignification. High temperature favored the oxidation but delignification was induced by the oxidation. For the paper reinforcement, chemical amounts were optimized according to the end user needs. For nanomaterial production, both oxidation and delignification were needed. The reaction had to generate a significant delignification and increase pulp carboxyl content higher than 1600 mmol/kg to be able to produce nanofibril material. The results showed new leads on the various times required for future industrial implementation.