Properties and stabilization mechanism of oil-in-water Pickering emulsions stabilized by cellulose filaments

Cellulose filaments (CFs) are produced from wood-pulp fibres through solely mechanical treatment. They are inhomogeneous materials comprising both relatively large fibre fragments and fine fibrils. CFs can stabilize oilin-water medium- and high-internal phase Pickering emulsions, where the presence of fibre fragments plays a critical role in emulsion stabilization by preventing CF fibrils from forming highly entangled structures. The emulsion properties are shown to be influenced by both the refining energy and CF concentration. CFs are distinct from cellulose nanofibrils (CNF) or microfibrillated cellulose (MFC), which flocculate and collapse owing to the entanglement of the homogeneous fibrous mass. Typically, other additives - surfactants or cellulose nanocrystals - are necessary to stabilize such emulsions. Further, lignin-containing CFs, produced from unbleached pulps, are particularly beneficial for emulsion stabilization at higher pH when the functional groups on lignin molecules are ionized. Our findings present CFs as potentially inexpensive, sustainable, and efficient emulsifiers for a wide variety of systems, from food to personal care products or engineering materials.