Sticky Hydrophobic Behavior of Cellulose Substrates Impregnated with Alkyl Ketene Dimer (AKD) via Sub- and Supercritical Carbon Dioxide

•Sub- and supercritical CO2 impregnation of AKD onto paper substrates is conducted.•The development of hydrophobicity was significant 2–3 days after impregnation.•Sticky hydrophobic surfaces was discovered > 140 days after the treatment.•Migration of AKD across the fiber surface causes reduction in the pore sizes.•Hydrogen bonding between AKD and cellulose is observed with FTIR.