Influenceof Vinyl Acetate Content on the Surface Hydrophobic Recovery of Ethylene Vinyl Acetate Copolymer after Plasma Modification

In this paper, two kinds of ethylene vinyl acetate copolymers (EVA) with different vinyl acetate (VA) contents were modified by plasma technique. The surface hydrophobic recovery and the nanostructure of the samples were evaluated by water contact angle measurement and positron annihilation lifetime spectroscopy, respectively. The water contact angle results indicated that higher VA content would result in faster hydrophobic recovery after plasma modification. The positron annihilation results indicated that two kinds of EVA samples exhibited similar o‐Ps lifetime, and EVA with higher VA content showed higher o‐Ps intensity. The results implied that the faster hydrophobic recovery after plasma modification should be contributed to the easier relaxation of chain segments for the EVA with higher VA content. Plasma modification is a powerful tool for surface modification, but the hydrophobic recovery limits the application of this technique. Ethylene vinyl acetate copolymers with different vinyl acetate (VA) contents were modified by plasma, and the hydrophobic recovery was evaluated by water contact angle measurement. It was found that higher VA content can lead to more free volume concentration, resulting in easier chain segment relaxation, which is in the charge of faster hydrophobic recovery.