Characterization of micro fibrillation process of cellulose and mercerized cellulose pulp

Abstract

Here we detail the fibrillation process for cellulose and mercerized cellulose pulps. Native and mercerized cellulose showed a high degree of purity as indicated by α-cellulose content measurement and XRD analysis. Furthermore, a stark change in fiber morphology indicated aggregation of fibrils on the surface due to mercerization. Fibrillation of pulp was carried out in the following subsequent steps: Disintegration, PFI refining, microgrinding by 20 passes and 60 passes in a SuperMassColloider respectively. Fiber samples were collected at every stage and highly uniform films were made by ultrafiltration and hot press method. The fibers and films made from fibers were then characterized by measuring physical properties, contact angle, thermal, mechanical, and SEM analysis. The main objective was to characterize the physical properties of the films made from different degrees of fibrillation. The films obtained were of fairly close grammage approximately 35 g m⁻². The target grammage was 40 g m⁻², and the slightly lower grammage indicated some fiber loss during the fabrication process. Additionally, it was observed that the density of the films increased with increasing degree of fibrillation from about 180 g m⁻³ to 455 g m⁻³ for cellulose I and 95 g m⁻³ to 385 g m⁻³ for cellulose II. Cellulose I films showed some contact angle to begin with which increased at every stage (14–64°), whereas cellulose II films did not display a contact angle until the final stage of fibrillation. The films also showed increasing strength and an evolution of tensile strength from initially displaying a tear behavior indicating poor bonding to typical micro fibrillated cellulose films behavior as the fibers became increasingly fibrillated. The ultimate tensile strength for cellulose changed from tear behavior with no defined break to 134.5 MPa. While on the other hand, the same change for cellulose II was a maximum of 75.1 MPa from tear behavior. Increasing fibrillation of fibrils in both cases showed a decrease in fiber size, well differentiated for the two types of pulps at every stage.