Macroscopic Quality Measurement of Plasma Treated Polystyrene through Computer Vision

Using a DC pulsed plasma for polymer surface treatment allows to obtain macroscopic modifications of the surface such as an important increase of the wettability i.e., reduction in hydrophobicity. In the same time, it yields microscopic variations of the surface structure that are mainly due to low depth chemical modifications even if only weak roughness changes appear. As a consequence this technique presents two major interests: an economical interest because of the low power consumption compared to other techniques like radio-frequency or microwave plasmas, and a non-invasive interest: very significant macroscopic treatment realized in soft conditions without degradation of the polymer. Applications are numerous: glue and painting production, health industry, aeronautics, wood industry, textile industry. To characterize the benefits of this technique for polymer surface treatment, we present an image processing tool that yields macroscopic measures of wettability, through the estimation of drop contact angles. The process is automated, precise and low-cost. The measurement of contact angle helps to infer microscopic properties from macroscopic features extracted via the unsupervised image processing technique. Results of macroscopic and microscopic studies on polystyrene surfaces allow to establish a macroscopic interpretation of the interaction between polymer and the DC pulsed plasma