Characterization of CO2 plasma-treated polyethylene surface bearing carboxylic groups

The surface modification of high density polyethylene by a CO2 microwave plasma is described with the aim of fixing carboxylic groups. The characterization is discussed in terms of functionalization, degradation, crystallization and cross-linking. The formation of carboxylic acids seems mainly favored by the presence of the CO2 active species. The degradation leading via chain scissions to the formation of volatile byproducts is shown to be heterogeneous by mainly affecting amorphous zones. The structural modification is associated with a twisting motion of macromolecular chains having defects to more organized conformations. Finally, cross-linking appears weak due to the absence of chromophoric sites and of VUV radiations in the plasma.