All-cellulose composites from alfa and wood fibers

Abstract

All-cellulose composites (ACCs) in which both matrices and reinforcing fibers are made from lignocellulose were successfully obtained from alfa (Stipa tenacissima L) and wood (Genus Betula) fibers. Matrices were prepared either from alfa or wood pulps that were dissolved in 8 wt% NaOH-water, while reinforcing fibers were alfa in both matrices. Prior to the dissolution, alfa and wood pulps were acid hydrolyzed in order to decrease cellulose degree of polymerization to 149 and 145, respectively. The degree of cellulose dissolution was 95-96 % for both alfa and wood dissolving pulps. X-ray diffraction (XRD) analysis confirmed the coexistence of cellulose I and II. The adhesion between the reinforcing fibers and both matrices was investigated using Scanning Electron Microscopy (SEM) and was found to be excellent. The density of ACCs decreased with the increase of the reinforcing fiber content for both types of matrices and ranged from 0.6 to 1.0 g.cm-3 leading to remarkably low-density ACCs. Young's modulus reached 3.8 and 4.2 GPa for the composites based on alfa and wood dissolving pulps, respectively, while yield stress reached 16 and 13.9 MPa, respectively.

All-cellulose composites via short-fiber dispersion approach using NaOH–water solvent

“…Porosity can be roughly estimated from the ratio of composite bulk to skeletal density, with the latter taken as 1.5 g/cm 3 . Porous composites with even lower densities, around 0.5 -1.0 g/cm 3 , were reported for allcellulose composites made from alfa fibers (Labidi et al 2019) and by impregnating pulp sheets with NaOH-urea-water (Piltonen et al 2016;Hildebrandt et al 2017). The reinforcement content plays the major role in the density of composites, and the DP of dissolved pulp has a minor effect (Figure 4).…”

“…The "short-fiber" all-cellulose composites can be produced via cellulose incomplete dissolution (many studies use microcrystalline cellulose) (Gindl and Keckes 2005;Duchemin et al 2009; Abbot and Bismarck 2010) or through fiber dispersion in cellulose solution (Ouajai and Shanks 2009;Yang et al 2010;Nadhan et al 2012;Labidi et al 2019). The latter mimics the production of conventional short-fiber polymer composites.…”

“…Until now, three solvents have been used to prepare all-cellulose composites with "short-fiber" approach. The most studied is lithium chloride/dimethylacetamide (LiCl/DMAc) (Gindl and Keckes 2005;Duchemin et al 2009; Abbot and Bismarck 2010) along with NaOH-water without additives (Labidi et al 2019) or with urea (Yang et al 2010;Nadhan et al 2012), and N-methyl-morpholine-N oxide monohydrate (NMMO) (Ouajai and Shanks 2009). Aside the solvent type and the grade of cellulose used for the matrix and as reinforcing fibers, other numerous processing parameters can be varied.…”

Gelation of cellulose-NaOH solutions in the presence of cellulose fibers

“…The second production pathway of all-cellulose composites presented in Figure 3.6 is based on randomly dispersed short fibers. Two approaches can be identified; the first one is based on partial dissolution of short fibers in a solvent (similarly to the pathway 1) (Gindl & Keckes 2005;Duchemin et al 2009a;Abbot & Bismarck 2010) and in the second approach the short fibers are dispersed in cellulose solution (Ouajai & Shanks 2009;Yang et al 2010;Nadhan et al 2012;Labidi et al 2019). The benefit of the latter approach is that it mimics the production of conventional short fiber polymer composites.…”

The effect of the natural degradation process on the cellulose structure of Moroccan hardwood fiber: a survey on spectroscopy and structural properties

“…Numerous non-destructive methods as X-ray diffraction (XRD) 10,12,13 , attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy 14,15 , Raman spectroscopy 10 , solid-state 13 C nuclear magnetic resonance (NMR 13 C/CP-MAS) measurements 10 , and differential scanning calorimetry (DSC) 13 , were employed in several works to quantify the cellulose crystallinity and understand the structural roles of cellulose in the recalcitrant, mechanical and biological properties of plant cell walls. Lionetto et al 15 , using X-ray diffraction and FTIR spectroscopy to quantify crystalline cellulose in lignocellulosic biomass, revealed that the crystallinity index (Cr.I.)…”