Assessing the Time Dependence of AOPs on the Surface Properties of Polylactic Acid

Plastics are artificial synthetic organic polymers that have been used in every area of daily life. However, because of their slow degradation rate, their use is contentious. The treatment of the surface of the sample is considered necessary as enzymatic or bacterial attach is not possible if the plastic surface environment is not ideal. The main topic of this work is the investigation of the effect of different advanced oxidation processes (AOP) on the near surface structure of polylactic acid (PLA) samples, which, in turn, can promote the adhesion of enzymes or bacteria for further biodegradation. The Advanced Oxidation Processes that have been used are Ultrasonication, UV photodegradation and Dielectric Barrier Discharge (DBD) plasma. After the treatments, the surfaces were characterized by Infrared Spectroscopy (IR), Drop Contact Angle (DCA), Confocal Laser Scanning Microscopy (CLSM) and X-ray Photoelectron Spectroscopy (XPS). Both ultrasonic and UV treatments have a significant impact on the surface properties of immersed PLA by removing the oxygen-containing groups of the polymer chain, albeit in different ways, while plasma tends to uncover oxygen groups on the surface. The influence of the pre-treatment on improving the adhesion of bacteria on the PLA surface has been proven using a pseudomonas knackmussii strain.