Sodium chloride and sodium dodecyl sulfate as additives to enhance dispersibility in microfibrillated cellulose

During drying, microfibrillated cellulose (MFC) can aggregate, lowering the tensile strength of MFC films and changing morphology. Therefore, the present study aims to evaluate additives as hydrogen bonding inhibitors on MFC to prevent aggregation. TEMPO-mediated oxidation followed by high-shear mixing was used to produce MFC. Never-dried (ND) MFC, only-dried MFC (DR), MFC with sodium chloride (D-Na) and sodium dodecyl sulfate (D-SD) were freeze-dried and analyzed. DR contained visible aggregates with lower stability in water (less than 85%) and produced the weakest films from all the samples. Even though D-Na had a particle size similar to D-SD, the tensile strength and strain at break of films were considerably lower. D-SD produced the most stable aqueous dispersion with smaller particles and porous structure. The presence of residual SDS increased tensile strength and stiffness of films by 28 and 48%, respectively compared to the ND films. The results show that D-SD was the most suitable additive to use with freeze-drying to preserve MFC physical properties while enhancing mechanical strength.