Modifications of the Polylactic Acid Surface Properties by DBD Plasma Treatment at Atmospheric Pressure

In this study, nitrogen plasma treatment at atmospheric pressure was used to modify the surface of polylactic acid (PLA), especially its low surface energy and wettability, which do not favor the interface adhesion with another material when blended. The dielectric barrier discharge (DBD) configuration was selected. Treatment time was varied, and induced chemical and topographical surface modifications were assessed. Attention was first focused on the effect of the treatment duration on the hydrophilicity and the topography of PLA. Results showed that plasma treatment enhanced the PLA surface hydrophilicity. The overall surface roughness was also found to be increased. Moreover, both properties rose with increasing treatment time. Thus, according to the Wenzel’s relation, the surface roughening contributed to the enhancement of the PLA hydrophilicity generated by plasma treatment. Then, the chemical surface changes induced by specific plasma activation were studied. Analyses pointed out the incorporation of hydrophilic groups such as nitrogen functional species after treatment. The stability of this treatment under air was also investigated: measurements showed that the hydrophobic recovery mainly occurred the first hours of storage.