Exploring the effects of low-pressure plasma and electron beam pre-treatments on surface esterification and liquid repellence of polylactic acid films

Polylactic acid (PLA) films were subjected to low-pressure plasma treatment and electron beam (e-beam) irradiation to promote subsequent fatty acid (FA) chloride grafting. This approach was investigated because surface esterification of PLA is currently constrained by the limited availability of reactive functional groups capable of serving as anchoring sites for fatty acids on the PLA surface. Water contact angle (WCA) measurements following plasma treatment showed a significant reduction, indicating enhanced surface polarity. After FA grafting, both WCA and olive oil contact angles increased notably, suggesting potential applications in packaging, particularly for improving easy-emptying properties. WCA remained significantly increased compared to untreated PLA even after multiple washing steps in petroleum ether. Determination of water vapour transmission rates (WVTR) showed no significant effect of FA grafting compared to the reference film. Graphical abstract