Lightweight and Strong Cellulose Materials Made from Aqueous Foams Stabilized by Nanofibrillated Cellulose

A lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified nanofibrillated cellulose (NFC). This material differs from other dry, particle stabilized foams in that renewable cellulose is used as stabilizing particles. Confocal microscopy and high speed video imaging show that the octylamine-coated, rod-shaped NFC nanoparticles residing at the air–liquid interface prevent the air bubbles from collapsing or coalescing. Stable wet foams can be achieved at solids content around 1% by weight. Careful removal of the water results in a cellulose-based material with a porosity of 98% and a density of 30 mg cm^–3. These porous cellulose materials have a higher Young’s modulus than porous cellulose materials made from freeze-drying, at comparable densities, and have a compressive energy absorption of 56 kJ m^–3 at 80% strain. Measurement with the aid of an autoporosimeter revealed that most pores are in the range of 300 to 500 μm