(570h) Engineering Sustainable Cellulose Materials with Supercritical Fluid Impregnation

Taking into consideration the environmental impact and sustainability factor, engineers are interested in employing renewable biomass to replace the dwindling fossil energy reserves. Cellulose is the most abundant renewable biopolymer in nature and constitutes roughly 50% of terrestrial biomass, known as lignocellulose. However, some unsuitable properties of cellulose, for instance, its sensitivity to water and sunlight, must be improved by a modification technique, where supercritical fluid (SCF) processes would be the best tools to enable the environmentally friendly character of cellulose as a multi-functionalized material. Understanding supercritical fluid technologies (SFT) is vital because its eco-friendly properties, adjustable solvation capabilities, and recyclability make it perfect for processing cellulose. This idea allows for efficient surface chemical modifications and functionalization while reducing the need for toxic solvents. Moreover, the supercritical state allows precise control over temperature and pressure, facilitating cellulose property manipulation for various applications, including sustainable packaging and biofuel production. From this point of view, carbon dioxide is usually the fluid employed because its critical state (31 ^oC, 73.8 bar) is readily attainable in industrial practice. Carbon dioxide's widespread availability, cost-effectiveness, safety, and ease of manipulation further solidify its position as the preferred solvent in supercritical impregnation processes across industries.

The present study evaluates the supercritical impregnation (SCI) of bio-based additives into paper substrates. Paper substrates are modified with additives to improve hydrophobicity (e.g., ethyl oleate) and UV absorption capacity (e.g., vanillin). The influence of process conditions on the efficiency of SCI of bio-based additives into paper substrates is evaluated at varying temperatures (40 °C to 80 °C), pressures (80 bar to 120 bar), and processing times (0.5 h to 24 h). The influence of co-solvents to ease the swelling of paper substrates is evaluated through screening species with unique molecular structures and properties. The fixed capacity of paper substrates to absorb additives is determined through gravimetric measurements, spectroscopic and microscopic characterizations. Fixed performance capabilities of the modified paper substrates are interrogated through mechanical, thermal, and sorption analysis. Collectively, the findings of the present study advance insights on process-structure-performance relationships toward engineering sustainable, cellulosic packaging materials modified from agricultural resources using environmentally cogent, chemical processes.