Tuning rheology and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils aqueous suspensions by addition of different acids. (1st June 2020)

• Record Type: Journal Article
• Authors: Alves, L.; Ferraz, E.; Lourenço, A.F.; Ferreira, P.J.; Rasteiro, M.G.; Gamelas, J.A.F.
• Is Part Of: Carbohydrate polymers. Volume 237(2020)
• Publication Date: 2020-06-01
• Subjects: Cellulose nanofibrils -- Charged nanofibrils -- Rheological properties -- Hydrogels -- Aggregation -- Acids -- Protonation -- Hofmeister series; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2020.116109
• Languages: English
• ISSNs: 0144-8617

Abstract

Highlights: Charged cellulose nanofibrils suspensions form strong gels at low consistency. Rheology and aggregation of charged cellulose nanofibrils change with pH conditions. CNF aggregation is controlled by the interaction of the anions of the acids used. Interactions between cellulose nanofibrils and anions follow the Hofmeister series. Abstract: The present work intends to study the variations in the rheological properties and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils (CNF) aqueous suspensions, as a function of changes in concentration and systematic changes in the pH, by addition of acids with different anions. It was found that CNF suspensions form strong gels at mass fractions higher than 0.35 % and the gel point is ca. 0.18 %. On the other hand, aggregation is enhanced at acidic pH conditions due to lower charge repulsion among fibrils, leading to an increase of the suspension viscosity. However, distinct rheological behaviours were presented by CNF suspensions as different acids were applied. It was found that phosphate ions resulted in significant aggregation leading to formation of particles of large size and very strong gels, at pH 2.3; distinctly, the presence of acetate ions resulted in lower aggregation, lower particle size and weaker gels, at the same pH value.