Leveraging Supercritical Fluids for the Functionalization of Cellulose Packaging Substrates

In recent years, plastic packaging materials have generated environmental concern due to a lack of recyclability, with tens of millions of tons directed to landfills annually in the United States. Cellulose, abundant in nature, is a biopolymer with emerging potential as a renewable alternative to plastic packaging material. Though cellulose-based materials are gaining traction in food packaging, cellulose is naturally hydrophilic and requires further treatment to enhance viability. Cardboard packaging materials are often treated with synthetic waxes to improve hydrophobicity, which makes recyclability difficult. Novel methods using greener technology and sustainable materials are becoming popular to mitigate environmental harm and prolong the life of expirable packaged goods. Supercritical fluids (SCFs) are compressible fluids comprising molecular species exceeding their critical pressure and critical temperature, combining the properties of gases and liquids and becoming an effective solvent. This project evaluates the feasibility of supercritical impregnation (SCI) processes of biobased additives into cellulose-based packaging materials for improved functionality.

Previous research has established the viability of Alkyl Ketene Dimer SCI, a surface sizing agent, into filter paper to improve hydrophobicity. The goal of the present investigation is to develop vanillin solute impregnation processes using supercritical carbon dioxide (scCO₂) for increased UV resistance of cellulose substrates as packaging material. Vanillin is initially dissolved in polar cosolvents and introduced into scCO₂ at different concentrations. SCI of cellulose is performed at varied pressures and temperatures to optimize process conditions. Preliminary investigations demonstrate SCI of vanillin into cellulosic substrates successfully increased sample UV absorbance as measured by UV-Visible spectroscopy. FTIR spectroscopy of SCI-modified cellulose identified IR bands associated with vanillin. Quartz crystal microbalance testing determined that vanillin is recoverable from cellulose with solvent flushing, indicating the potential recyclability of vanillin-impregnated packaging material. This study will impact cellulosic packaging material properties and limit plastic pollution if the proposed SCI process reaches a manufacturing scale.