Biobased insulating materials from rapeseed harvest residues: Effect of fiber extraction treatment on final properties

Abstract

In this work, lignocellulosic fibers from rapeseed harvest residues were used to develop bio-based insulating foams as an alternative to petroleum-based materials, investigating the influence of the fiber extraction method on the final behavior of the prepared foams. Particularly, alkaline and mechanical treatments were applied to the raw material, evaluating their effect on the fiber properties as well as on density and mechanical behavior under compression of the foams prepared with the extracted fibers, using a Doehlert experimental design. Stronger alkaline treatments (longer time and higher NaOH concentrations) led to fibers with higher crystallinity and smaller diameters due to the partial removal of lignin and other non-cellulosic compounds. Foams prepared with extracted fibers presented low apparent densities (0.050 − 0.085 g/cm3) and comparable thermal conductivity (0.064 ± 0.002 W/mK) and mechanical properties (elastic modulus: 0.267 – 2.183 MPa; compressive strength: 0.019 – 0.177 MPa; and toughness: 9.286 – 89.039 kJ/m3) to those reported in the literature for commercial foams. ANOVA testing suggested that both NaOH concentration and soaking time showed a significant positive effect on mechanical properties, obtaining more resistant foams as the treatment intensity increased. In addition, further analysis performed in selected samples suggested that alkaline treatments at mild conditions improve the foam water sensitivity. Therefore, the selection of the fiber extraction treatment variables appears as an important factor for the obtention of bio-based foams with suitable properties as an alternative to replace non-biodegradable materials.