Effect of Dissolution Time on the Development of All-Cellulose Composites Using the NaOH/Urea Solvent System

• Published in: Polysaccharides Vol. 4; no. 1; pp. 65 - 77
• Main Authors: Delgado, Juan Francisco, Salvay, Andrés Gerardo, Arroyo, Silvana, Bernal, Celina Raquel, Foresti, María Laura
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-03-2023
• Subjects: all-cellulose composites; Aqueous solutions; Cellulose; Cellulose fibers; Dissolution; dissolution time; Environmental impact; Fibers; Filter paper; Hot pressing; Hydration; Mechanical properties; Methods; NaOH/urea solvent system; Optical properties; partial dissolution method; Polymerization; Polymers; Porosity; Scanning electron microscopy; Sodium hydroxide; Solvents; Urea; United States > US; Argentina
• ISSN: 2673-4176; 2673-4176
• DOI: 10.3390/polysaccharides4010005

Innovative and sustainable all-cellulose composites (ACCs) can be obtained by partial dissolution of cellulosic fibers and regeneration of the dissolved fraction. Among cellulose solvents, sodium hydroxide/urea solutions are recognized as promising low-environmental impact systems. In this work, filter paper (FP) was dissolved with a 7 wt% NaOH/12 wt% urea aqueous solution, kept at −18 °C for different time intervals, regenerated with distilled water and finally dried under different conditions. The developed films were characterized in terms of morphology, porosity, optical properties, crystalline structure, hydration and mechanical properties. The porosity of the composites decreased with dissolution time due to the progressive filling of voids as the cellulosic fibers’ surface skin layer was dissolved and regenerated. Samples treated for 4 h showed the minimum values of porosity and opacity, high hydration and a substantial change from cellulose I to cellulose II. Hot pressing during drying led to relevant improvements in ACCs stiffness and strength values.