Microfibrillated Cellulose Moisture Sorption Fundamentals in Fiber Packaging
Microfibrillated cellulose moisture sorption degrades barrier performance at high humidity, requiring chemical cross-linking and verified compliance dossiers.
Cellulose Nanofibrils
Fibrillar Structure
Delaminated plant fibers broken down into high-aspect-ratio elements with micro-fibrillar networks constitute high-surface-area bio-based additives for paper coatings and structural reinforcement. Mechanical refining under severe shear action generates cellulose nanofibrils from bleached wood pulp, creating flexible strands that range between five and fifty nanometers in diameter. Suspensions of these particles form entangled networks in aqueous media, increasing web density when added to papermaking furnish or applied as surface treatments.
Application boundaries remain defined by high slurry viscosity at low solid content, which limits solids loading in wet-end additions to less than three percent by weight.
Rheological Behavior
Shear-thinning properties govern fluid transport through pumps and coating nozzles during application. Viscosity drops sharply as shear rates increase, allowing uniform deposition of cellulose nanofibrils onto paperboard substrates at high machine speeds. Hydroxylated surfaces bind water tightly, extending drying times and requiring additional energy in thermal drying sections.
Dewatering resistance rises steeply when fine fiber fragments fill inter-fiber voids within the forming fabric.
Barrier Performance
Dense hydrogen bonding within dried films creates effective barriers against oxygen gas and grease molecules. Water vapor transmission rates remain relatively high due to the hydrophilic nature of un-derivatized cellulose nanofibrils under elevated ambient humidity. Cross-linking additives or hydrophobic overcoats prevent moisture-induced swelling when films face wet tropical environments.