Characterizing highly fibrillated nanocellulose by modifying the gel point methodology

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Characterizing nanocellulose (NC) fibre length is challenging, often relying on indirect aspect ratio calculations.
• Existing gel point methodologies struggle with highly charged nanofibres and difficult-to-observe sediment layers.

Purpose of the Study:

• To modify and validate the gel point methodology for accurate nanocellulose fibre length characterization.
• To improve the measurement of aspect ratio for highly charged and low-diameter cellulose nanofibres.

Main Methods:

• Modified the gel point methodology by incorporating Crystal Violet dye for improved visualization of sedimentation lines.
• Optimized sedimentation times to ensure complete fibre settling for both low and high fibrillated NC (LF-NC, HF-NC).
• Validated the modified method by assessing the influence of pH and salt concentration (CaCl2) on fibre behaviour.

Main Results:

• The modified method provides reproducible gel points: 2 days for LF-NC and 8 days for HF-NC.
• Sedimentation time increases with fibre fibrillation, charge, and decreased fibre dimensions.
• Low pH and CaCl2 caused HF-NC to flocculate, significantly decreasing the gel point.

Conclusions:

• The modified gel point methodology offers a valuable tool for accurate dimensional characterization of challenging cellulose nanofibres.
• This technique enhances the ability to measure the aspect ratio of highly charged and low-diameter NC.
• The study highlights the differential behaviour of LF-NC and HF-NC during sedimentation.