Polylactic acid surface activation by atmospheric pressure dielectric barrier discharge plasma

Polylactic acid (PLA) is suitable for applications in packaging and biomedicine due to its biodegradability. To improve PLA surface adhesion a plasma-chemical treatment using nonthermal plasma generated in ambient air via diffuse coplanar surface barrier discharge (DCSBD) was used. The optimal treatment time and power were investigated. Interaction between active plasma species and the polymer surface, and the resulting surface changes were studied by contact angle measurement, surface energy determination, FTIR, and XPS. The most hydrophilic surface was obtained after only 3–4 s treatment. Treatment up to 10 s did not damage the polymer but longer treatments (30 and 60 s) caused partial degradation. The plasma broke C-C/C-H bonds and formed more C-O, O-C=O and C-O-C bonds. During storage surface oxygen decreased and a negligible amount of nitrogen was adsorbed. The oxygen-containing functional groups probably sank into the PLA volume after treatment.