CNFs from twin screw extrusion and high pressure homogenization: A comparative study

Cellulose nanofibrils (CNFs) from oxidized never dried Eucalyptus pulps have been produced by using twin screw extrusion (TSE) and high pressure homogenizer (HPH), and their properties were compared. CNFs from TSE are produced at 10% solid content and then diluted to 1% for purpose of comparison against HPH. The nanosized fraction (NF) was around 90% for CNFs from HPH compared to 70% when TSE was used. Difference in the fibrillation extent has led to a higher transparency degree for CNFs gel from HPH. However, the rheological properties of two CNFs gels are quite similar with a solid-like aspect. The elastic modulus is one order of magnitude higher than viscous modulus and nearly frequency-independent. Analysis of the nanosized fraction with AFM has revealed long nanosized fibrils 3-4 nm in width for both CNFs types. When mixed with waterborne polymer dispersion, transparent to translucide nanocomposite films were obtained. However, the reinforcing potential of CNFs from HPH has been shown to be stronger than that from TSE.