Contribution of surface energy and roughness to the wettability of polyamide 6 and polypropylene film in the plasma-induced process

Plasma-induced etching and chemical vapor coating processes are well-known technologies that modify the wetting properties of polymeric surfaces by engineering the surface roughness and surface energy. The contributing effect of plasma treatment for O-2 etching and hexamethyldisiloxane (HMDSO) vapor coating on the wetting properties was investigated for polyamide 6 (PA6) and polypropylene (PP) substrates. The surface energy components of PA6 and PP were analyzed by the Owens-Wendt model, and were associated with the wettability of water and diiodomethane. With the introduction of roughness by the O-2 etching process without HMDSO coating, the wettability of PA6 substrate was enhanced while that of PP was deteriorated when they were observed after 20 days aging. When the surface was etched for 7min or longer with the subsequent coating with HMDSO, both PA6 and PP lost hydrophilic property, giving water contact angle of 180 degrees. The wettability was examined for the varied treatment conditions and as a function of average nano-pillar length. This study helps better understand the interactions between the surface energy and roughness of polymeric materials, and their influence on surface wettability.