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submitted on 11.06.2018 and posted on 14.06.2018by Elisa S. Ferreira, Camila Alves Rezende
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.