CO₂, H₂O, and CO₂/H₂O Plasma Chemistry for Polyethylene Surface Modification

During a cold plasma treatment, a polymer surface is involved in many reactions, such as degradation and functionalization. CO 2 plasma treatment leads to carboxylic acid function fixation onto high-density polyethylene surface. Attempts are done to optimize the concentration of these last functions by using CO 2 /H 2 O plasmas. By fragmentation and recombination reactions between plasma species, we hope to create new species such as carboxylic acids precursors (CO + OH or CO 2 + H) that are able to increase the surface carboxylic density. Spectrochemical quantification and XPS analysis measure the surface functionalization whereas the plasma composition and plasma−polymer interactions are analyzed by mass spectrometry. The surface functionalization results show a decrease of carboxylic acid density whatever the water proportion and the discharge power explained by a mass spectrometry study. Thus, no recombination reaction leading to the formation of COOH plasma species occurred in the plasma phase. During the polyethylene treatment with CO 2 plasma, evidence of degradation is also shown by mass spectroscopy (atomic and molecular hydrogen formation in the plasma phase). A correlation done between weight-loss measurement and the atomic oxygen (O 3 P and/or O 1 D) proportion in the CO 2 plasma showed the significant role of the latter on the surface degradation mechanism.