In-situ modification of cellulose nanofibrils by organosilanes during spray drying

•Modifying CNFs with organosilanes during spray drying changed the morphology of dried CNF powders modestly.•The silane treatment reduced the size of dried CNF powders and changed the size distribution.•GPS treated CNFs displayed lower dispersion component of surface energy compared to control CNFs.•VTS treated CNFs showed increased acidity and basicity at higher silane concentration, while GPS only increased the basicity of CNFs.

Cellulose nanofibrils (CNFs) have shown their potential as the sustainable choice for reinforcements in thermoplastic composites. Studies on surface properties are important because they directly relate to the compatibility between CNFs and polymer matrices. In this study, CNF suspensions were treated with two different organosilane functionalities before being spray-dried (SD). Three concentration levels of organosilane solution were applied based on the mass of the CNFs in suspension: 1 wt. %, 3 wt. % and 5 wt. %. Morphological and surface properties of the CNFs were measured to understand changes induced by the organosilane modification. Scanning electron microscopy analysis shows some aggregation of larger particles as well as many small twisted rectangular particles. Particle size distribution analysis (PSD) indicates certain differences among treated and untreated CNFs. Inverse gas chromatography (IGC) reveals that the organosilane treatment reduces the dispersion component of surface energy of dried CNFs and changed the acid-base characteristic of CNFs by the attachment of different functional end-groups.