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

Abstract

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.

Nanocellulose properties and applications in colloids and interfaces

“…CNF and CNC by themselves do not have strong interfacial activity to produce stable foams, however amphiphilic behavior can be imparted by either polymer adsorption or by chemical surface modification, for example, by attachment of hydrophobic moieties. For instance, aqueous foams stabilized with up to 1 wt% CNF were prepared by adsorbing positively charged octylamine on the surface of the fibrils followed by introduction of air bubbles in the system through mixing and final freeze drying to yield highly porous, lightweight cellulose foams (pore size ~300-500 μm) (Cervin et al, 2013).…”

“…Some recent approaches include the control of the morphology of cellulose foams by preparing precursor aqueous foams (Cervin et al, 2013) or Pickering emulsions (Tasset et al, 2014).…”

3D-oriented fiber networks made by foam forming

“…Recently, foam forming was studied extensively to develop the understanding of foam-fiber interactions (Al-Qararah et al 2012Lappalainen and Lehmonen 2012;Lappalainen et al 2014;Mira et al 2014) and also to find the potential applications of this technology in papermaking Lehmonen et al 2013;Poranen et al 2013) as well as other specialty products, e.g., filters and insulators (Cervin et al 2013;Jahangiri et al 2014). Foam was introduced to the paper industry already in the mid-1960s.…”

Morphology of Burned Ultra-low Density Fiberboards

“…Cellulose fiber (Frenette et al 1996;Cervin et al 2013), hemp, wood chips, wood fibers (Rowell et al 1995;Kawasaki et al 1998), and kenaf (Xu et al 2004;Xie et al 2015) are all used as raw materials to produce bio-based insulation. Ultra-low density fiberboards (ULDFs) are one type of bio-based insulation material.…”