Multiscale characterisation of cellulose nanofibril networks using three 3D imaging methods.

Area of Science:

• Materials Science
• Food Packaging Technology
• Nanotechnology

Background:

• Cellulose materials offer a sustainable alternative to plastic in food packaging.
• Hydrophilic nature of cellulose can lead to poor barrier properties, impacting food shelf-life.
• Bilayer materials using microfibrillated cellulose (MFC) films show promise for enhanced barrier performance.

Purpose of the Study:

• To investigate the microstructural properties of MFC films in bilayer food packaging materials.
• To understand how microstructural characteristics influence barrier properties.
• To present a comprehensive 3D representation of MFC-based bilayer materials.

Main Methods:

• Utilized a multiscale approach combining synchrotron X-ray micro-/nanotomography and FIB-SEM tomography.
• Investigated the 3D microstructure of two distinct bilayer materials produced with different MFC grades.
• Analyzed parameters such as porosity, pore connectivity, and interfacial contact area.

Main Results:

• Achieved the first full 3D representation of MFC-based bilayer materials.
• Demonstrated that both MFC films exhibit dense structures with negligible porosity.
• Confirmed the absence of pore connectivity through the film thickness.
• Identified that films made with smaller MFC fibrils result in more homogeneous, less porous layers with increased contact surface area.

Conclusions:

• MFC films possess dense, non-porous microstructures suitable for improving barrier properties in cellulose-based food packaging.
• The choice of MFC fibril size significantly impacts layer homogeneity, porosity, and interfacial contact, influencing overall barrier performance.
• Advanced 3D imaging techniques are effective for characterizing complex microstructures in novel packaging materials.