Surface energy modification for coating adhesion improvement on polypropylene

Polypropylene (PP) has poor superficial properties making a pre-treatment before coating the paint film necessary. The pre-treatment related to surface improvement most widely used in the industry is the flame treatment due to its capacity to achieve the necessary level of surface energy. This work is to study the effect of the flame treatment in the adhesion increase for painting films applied on polypropylene substrates. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), dyne test inks, contact angle, resistance to adhesion by engraving and washing were employed to evaluate the flame treatment. The morphological, chemical and physical analysis presented superficial modification, the formation of new functional groups and improvements on adhesion between substrates and paint film, respectively. These results proved the efficacy of the flame treatment in the increase of the surface energy and in the adherence of the coatings applied to the PP substrates.