Flame treatment on plastic: A new surface free energy statistical prediction model and characterization of treated surfaces

Flame treatments on polymeric materials improve surface free energy (SFE) and consequently the wettability and adhesion of coatings, metallizations, varnish and glues. In this paper, using a statistical methodological approach based on DoE technique and multivariate analysis of flame treatment process parameters, a mathematical model of SFE and wettability is obtained. Contact angle experimental technique was applied to measure the improvement of wettability and SFE. In order to study the oxygen diffusion within the polymer, morphological variation and change of its structure, analyses of treated surface sample were carried out on micro and nano scales. X-ray photoelectron spectroscopy analysis, performed before and after flame treatment, showed the O-radical group improvement on a polymeric surface. Focused ion beam and transmission electron microscopy technology were used to determine the exact thickness of the polymeric material influenced by flame treatment, identifying a composite change on nano scale and a porosity change on microscale.