Browsing by Subject "nanocellulose"

The stability and properties of oil-in-water Pickering emulsions formed by hexadecane and water and stabilized by TEMPO-oxidized cellulose nanofibrils (TCNF), anionic lignin nanoparticles (ALNPs), cationic lignin nanoparticles (CLNPs), and their different combinations were investigated. The effects of varying the ALNPs and CLNPs to TCNF ratios, pH, and the order of mixing on Pickering emulsion stabilization were evaluated. The overall aim of the research was to study whether the combination of lignin nanoparticles (LNPs) and TCNF in Pickering emulsions present a synergistic stabilizing effect. ALNPs were produced by the anti-solvent nanoprecipitation method, whereby CLNPs were obtained by coating ALNPs with cationic lignin using the adsorption method. The emulsions were characterized by their morphology and droplet size distribution, zeta potential, viscosity, stability with aging, and the amount of stabilizers unadsorbed on the droplet surface. Negatively charged ALNPs induced surface hydrophobicity in TCNF-stabilized emulsions, resulting in emulsions with small, individualized droplets and improved physical stability. Positively charged CLNPs did not improve the properties of TCNF-stabilized emulsions due to charge neutralization of stabilizers and weakly flocculated oil droplets. The combination of ALNPs and TCNF in the emulsion did not lead to synergistic stabilization as ALNPs alone produced more stable emulsions with small-sized droplets. The stability of emulsions also increased as the ratio of ALNPs was increased. All the emulsions stabilized by ALNPs and TCNF were stable against coalescence yet creaming appeared during 30 days of storage. Emulsions irrespective of the type of stabilizers were most stable at pH 8. Moreover, a stable emulsion with a small droplet size could be formed when the ALNPs were added at the same time with TCNF but not mixed sequentially.