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

DELGADO, JUAN FRANCISCO; SALVAY, ANDRÉS GERARDO; ARROYO, SILVANA; BERNAL, CELINA RAQUEL; FORESTI, MARÍA LAURA

Polysaccharides

MDPI

Lugar: Basel; Año: 2023 vol. 4 p. 65 - 77

Innovative and sustainable all-cellulose composites (ACCs) can be obtained by partialdissolution 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 underdifferent conditions. The developed films were characterized in terms of morphology, porosity, opticalproperties, crystalline structure, hydration and mechanical properties. The porosity of the compositesdecreased with dissolution time due to the progressive filling of voids as the cellulosic fibers’ surfaceskin layer was dissolved and regenerated. Samples treated for 4 h showed the minimum values ofporosity and opacity, high hydration and a substantial change from cellulose I to cellulose II. Hotpressing during drying led to relevant improvements in ACCs stiffness and strength values.