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

Prior research has shown that cellulose nanofibrils (CNFs) can be produced from various sources and processing techniques. Established knowledge includes the use of high-pressure homogenization (HPH) to create CNFs with high fibrillation. However, the application of twin screw extrusion (TSE) as an alternative method remains underexplored. This gap motivated the investigation of TSE for CNF production. No prior work had resolved how TSE compares to HPH in terms of fibrillation and composite properties. The study aimed to address this uncertainty by comparing the two methods. The goal was to determine if TSE could yield CNFs with comparable or superior characteristics to HPH. The need for alternative, scalable methods in CNF production is evident from the literature. This paper contributes by evaluating TSE alongside HPH for CNF synthesis.

The study aimed to compare twin screw extrusion (TSE) and high-pressure homogenization (HPH) for producing cellulose nanofibrils (CNFs) from oxidized Eucalyptus pulps. The specific problem addressed was the lack of comparative data on the effectiveness of these two methods in CNF production. The motivation stemmed from the need for scalable and efficient CNF synthesis techniques. The authors sought to evaluate the fibrillation extent, transparency, and reinforcing potential of CNFs produced via each method. The study also aimed to assess the rheological properties of the resulting CNF gels. By comparing the nanosized fractions and composite films, the researchers intended to identify the method with superior functional properties. The comparison was designed to inform future CNF production strategies. This approach aligns with the broader goal of optimizing CNF synthesis for industrial applications.

The study utilized twin screw extrusion (TSE) and high-pressure homogenization (HPH) to produce cellulose nanofibrils (CNFs) from oxidized Eucalyptus pulps. CNFs from TSE were initially produced at 10% solid content and then diluted to 1% for comparison with HPH. The nanosized fraction (NF) was measured to evaluate fibrillation extent. Atomic force microscopy (AFM) was employed to analyze the morphology of the nanosized fibrils. Rheological properties of the CNF gels were assessed to determine their solid-like characteristics. Transparency measurements were conducted to compare the optical properties of CNF gels from both methods. The reinforcing potential of CNFs was evaluated by mixing them with waterborne polymer dispersions to form composite films. The study focused on quantifying differences in fibrillation, transparency, and composite performance between the two methods.

The nanosized fraction (NF) was approximately 90% for CNFs produced via high-pressure homogenization (HPH) compared to 70% for those from twin screw extrusion (TSE). This difference indicated a higher fibrillation extent in HPH-derived CNFs. The CNF gels from HPH exhibited a higher transparency degree than those from TSE. Both CNF gels displayed a solid-like aspect with similar rheological properties. The elastic modulus was one order of magnitude higher than the viscous modulus for both CNF gels. Atomic force microscopy (AFM) analysis revealed fibrils of 3-4 nm in width for both CNF types. Transparent to translucent nanocomposite films were obtained when CNFs were mixed with waterborne polymer dispersions. The reinforcing potential of HPH-derived CNFs was found to be stronger than that of TSE-derived CNFs.

The study demonstrated that high-pressure homogenization (HPH) produced cellulose nanofibrils (CNFs) with a higher nanosized fraction and greater fibrillation extent compared to twin screw extrusion (TSE). The CNF gels from HPH exhibited higher transparency and stronger reinforcing potential in composite films. Both CNF gels showed a solid-like aspect with similar rheological properties. The elastic modulus was significantly higher than the viscous modulus for both methods. Atomic force microscopy (AFM) confirmed the presence of 3-4 nm wide fibrils in both CNF types. The authors suggest that HPH may be more effective for CNF production in terms of fibrillation and composite performance. The study highlights the importance of method selection in CNF synthesis for specific applications. These findings provide insights into optimizing CNF production techniques for industrial use.