Simple Preparation of Cellulosic Lightweight Materials from Eucalyptus Pulp

Cellulosic foams and aerogels are tridimensional materials prepared from cellulose fibers and nanostructures that display interesting properties, such as extremely low density, high fluid permeability, sound and heat insulation. Currently, the most common techniques to obtain such porous matrices are gel or foam forming, followed by freeze-drying or critical point drying, which are energy and time-consuming processes for solvent removal. In this work, we present a new methodology to produce cellulosic lightweight materials from eucalyptus pulp, using cellulose fibers partially hydrolyzed with sulfuric acid. This method is based on a drying step easily performed at mild temperatures around 60°C in a convection oven and eliminates the need of more sophisticated drying techniques. In addition, the procedure does not require the use of surfactants or special foam forming equipment. Micro-CT and FESEM analysis showed the formation of a porous and lightweight material (density as low as 0.15 g/cm³), where the fibers are randomly assembled in a 3D-network with a few contact points. Mechanical testing reveled that foams of hydrolyzed fibers have great performance under compressive strain, with high mechanical energy absorption (ca. 360 kJ/m³). This purely cellulosic material is suitable for the incorporation of particles or functional groups aiming a wide range of final applications.