Three-dimensional microstructural properties of nanofibrillated cellulose films

Area of Science:

• Materials Science
• Polymer Science
• Biomaterials

Background:

• Nanofibrillated cellulose (NFC) films are promising oxygen barriers for packaging.
• Their hygroscopic nature limits practical applications.
• Understanding NFC microstructure and humidity effects is crucial.

Purpose of the Study:

• To assess the 3D microstructure of NFC films from Pinus radiata kraft pulp.
• To investigate structural changes with varying relative humidity (RH).
• To correlate microstructure with oxygen barrier properties.

Main Methods:

• X-ray microtomography (X-μCT) for 3D microstructure analysis.
• Computerized image analysis, scanning electron microscopy, and laser profilometry.
• In-situ characterization using a humidity chamber with X-μCT.

Main Results:

• X-μCT effectively assessed NFC film microstructure.
• Oxygen transmission rate (OTR) increased from 3.7 to 12.4 mL m⁻² day⁻¹ as RH rose from <60% to 80%.
• Increased RH caused film swelling and increased porosity, degrading barrier performance.

Conclusions:

• NFC film microstructure is sensitive to relative humidity.
• Humidity-induced swelling and porosity changes significantly impact oxygen barrier properties.
• Characterization techniques provide insights into NFC film behavior under varying humidity.