Effect of the oxidation treatment on the production of cellulose nanofiber suspensions from Posidonia oceanica: The rheological aspect

•CNF were prepared from Posidonia oceanica balls and leaves.•TEMPO mediated oxidation for the preparation of CNF was studied.•The effect of oxidant dose in TEMPO mediated oxidation was studied.•The CNF gel was produced via ultrafine friction grinding process.•Physicochemical properties and the viscoelastic behavior of CNF suspension were studied.•The studied CNF suspensions exhibited gel-like, shear-thinning properties. Different grades of cellulose nanofibrils (CNF) were prepared from Posidonia oceanica balls and leaves (POB and POL). Pretreatment using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation was performed to facilitate the fibrillation during ultrafine friction grinding process. The ensuing CNF batches were compared in terms of morphology and degree of fibrillation. The rheological properties of the produced CNF suspensions were also analyzed for varying doses of sodium hypochlorite used during the TEMPO- mediated oxidation procedure. The stronger fibrous network structures were formed when increasing the oxidant concentration, which was confirmed by the increase of the storage moduli value. P. oceanica balls were found to undergo stronger fibrillation and, consequently, to form stronger networks, compared to P. oceanica leaves, when using equivalent concentration of the oxidizing agent.