Preparation of oxidized polyethylene wax from polyethylene wax by SCCO2-assisted foam method: structural characteristics, reaction mechanism and properties

Polyethylene wax (PEW) serves as a versatile material modifier, and the newly acquired polarity functions after functionalization are of great interest. Furthermore, exploring methods to enhance product purity further is necessary. The rate of reaction between oxygen and PEW depends on both the diffusion rate of oxygen in the polymer and the thermodynamic properties of the reaction. To address these challenges and investigate changes in reaction mechanisms and properties, we employed supercritical carbon dioxide foaming to facilitate PEW oxidation while utilizing DFT theory to calculate oxidation reaction pathways and thermodynamic properties. The acid value of foamed PEW at 16 MPa and 115 °C increased by a factor of 2.7 compared to non-foamed PEW after 6 h of oxidation, indicating that foaming acted as an aid during this process. The generation of −OH, C = O, −CHO, and −COOH during the oxidation process was mutually confirmed through comprehensive analysis including FTIR, NMR spectroscopy, as well as other characterizations and calculations. Oxidized PEW (OPE) exhibited a maximum reduction in water contact angle (WCA) by 49°, a maximum decrease in crystallinity by 26.32