AbstractIn order to improve the properties of thermomechanical pulp (TMP), the influences of the TEMPO (2,2,6,6-tetramethylpiperidyl-1-oxyl radical)-mediated oxidation on recycled TMP properties were investigated, and the impacts of recycling process on TEMPO-mediated oxidized TMP properties were studied as well. The results showed that TEMPO-mediated oxidation is an effective way to enhance the recycled TMP inter-fiber bonding dependent properties due to the introduction of carboxylic acid groups onto pulp, while the oxidation had some negative impacts on the tear index, zero span tensile index, and brightness. The oxidation-recycling (O-R) process had remarkable adverse impacts on TMP compared with the recycling-oxidation (R-O) process. The tensile, burst, tear strengths, as well as the zero-span tensile strength dropped sharply when oxidized TMP was recycled, and the physical strength properties decreased with the increasing recycling times. The opacity was improved after the O-R treatment, although the O-R treatment had an adverse impact on the pulp brightness.