Characterization of cellulose nanocrystals extracted from El Diss and El Retma local plants and their dispersion in poly(vinyl alcohol-co-ethylene) matrix in the presence of borax

This study aims to investigate the potential of two local fibers, namely El Diss and El Retma, which are abundant in the mountains of North Africa (Setif, Algeria), to provide cellulose nanocrystals (CNCs). Then, the isolated CNCs from El Diss were used as a reinforcement for a poly(vinyl alcohol-co-ethylene) matrix (EVOH) in the absence and in the presence of borax which was added to improve the interactions between the CNCs and the matrix. The extracted CNCs from both El Diss (CNCD) and El Retma (CNCR) were characterized by Zeta-sizer analysis using dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electronic microscopy. Also, untreated EVOH/CNCD nanocomposites and borax-treated EVOH/CNCD/BOR have been characterized using FTIR, differential scanning calorimetry (DSC) analyses, and by the study of their water absorption behavior. The DLS analysis provided the transversal length of the particles and showed that the surface of the obtained CNCs is negatively charged due to the presence of sulfated ions. Also, FTIR results confirmed the elimination of extra cellulosic substances, whereas TGA proved that the degradation of CNCs occurs at relatively lower temperatures compared with the neat fibers. The incorporation of borax to EVOH/CNCD nanocomposites showed its efficiency in improving the interactions at the interface between EVOH and the CNCD, which significantly affected the material's thermal properties as concluded from DSC results and their water absorption behavior.