Cellulose, a key component of plant biomass, presents a sustainable alternative to synthetic packaging due to its biodegradability and low environmental footprint. However, its inherent hydrophilicity limits performance in moisture-sensitive applications. This study evaluates supercritical impregnation (SCI) of eco-friendly additives to enhance cellulose hydrophobicity. Ethyl oleate, an edible GRAS-designated functional additive, was impregnated into cellulosic substrates under varying temperatures (40 - 160 °C), pressures (80 - 200 bar), and durations (10 - 90 min). The role of polar and non-polar cosolvents in promoting cellulose swelling and additive sorption was examined. Gravimetric analysis quantified loadings up to ~0.9 g g⁻¹. Thermogravimetric analysis (TGA) was conducted on unmodified (Sample A) and SCI cellulose (Samples B and C) at 110 °C, 120 bar for 10 min, with analysis performed 1- and 5-days post-fabrication. Sample A exhibited two-stage degradation: moisture loss (~2.7%) from 25 – 93 °C and major decomposition (~87.7%) from 254.8 – 398.2 °C. SCI-samples exhibited significantly greater total weight loss, indicating ethyl oleate sorption. TGA-derived additive loadings (B: 0.82 g g⁻¹; C: 0.74 9 g g⁻¹) closely matched gravimetric values (B: 0.86 g g⁻¹; C: 0.78 g g⁻¹), confirming sorption and validating the gravimetric method. Additionally, a shift in thermal degradation profile of modified samples indicated improved thermal stability. FTIR spectroscopy revealed the integration of ethyl oleate through the emergence of its characteristic vibrational modes, notably the ester carbonyl (C=O) stretching at 1738 cm⁻¹ and asymmetric/symmetric methylene (C–H) stretching bands at 2921 and 2856 cm⁻¹, respectively. Alongside this, a substantial decrease in the broad O–H stretching envelope (3600 – 3100 cm⁻¹) was observed, indicative of disrupted intermolecular hydrogen bonding within the native cellulose supramolecular architecture, consistent with the formation of hydrogen-bonded complexes and partial substitution or steric hindrance at hydroxyl binding sites. XRD revealed reduced internal crystallinity, validating matrix interference. SEM showed pore filling. Sorption analysis demonstrated reduced moisture-uptake, while kinetic modeling displayed faster equilibration. Contact angles up to 109° substantiated improved hydrophobicity. This study highlights SCI’s potential for advancing sustainable, high-performance cellulose-based packaging.
