Surfactant-assisted foam-forming of high performance ultra-low density structures made from lignocellulosic materials and cellulose nanofibrils (CNFs)

From the paper

Abstract

Bio-based lightweight materials are promising replacements for petroleum-based foams in building and packaging applications. In this work, we developed a surfactant-assisted foam-forming method to manufacture lightweight materials based on lignocellulosic fibers (thermomechanical pulp (TMP), refined wood fibers (RWF) and pine flour (PF)) enabled by cellulose nanofibrils (CNFs). Sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB) at 1g/L concentration was mixed with different concentrations of CNFs in a blender followed by the addition of a pre-determined amount of TMP, RWF or PF. The preparation of hybrid foams using TMP/PF, TMP/RWF, and TMP/PF/RWF at different weight fractions was also investigated. Results showed that among the three tested natural fibers, TMP was the best for the preparation of low-density foamed materials, with densities ranging from 11 to 45kg/m³ in the case of foams made with SDS and 16-90kg/km³ for those made with CTAB. Thermal conductivity of the prepared foams was between 0.031W/m.K and 0.055W/m.K depending on the density and the porosity of the foams. Foams made with high solids content (4-6wt.%) exhibited excellent sound absorption coefficients (0.96-1 at 3500Hz). Water stability and mechanical properties of the resulting bio-foams were significantly improved when increasing CNF and solids contents. All foams exhibited antifungal properties against Trametes versicolor. Additionally, the hybrid foams exhibited good and competitive properties. These low-density foams enabled by the excellent bonding capability of CNFs could thus be potentially used to provide antifungal resistance as well as acoustic and thermal insulation.