Modification of polypropylene surfaces by flame treatment

Abstract The changes induced on the surface of polypropylene homopolymer following flame treatment have been studied. Surface compositions were determined using x‐ray photoelectron spectroscopy and compared to surface free energies estimated from contact angle measurements. The effect of air‐to‐gas ratio, total flow rate, contact time with the flame and the distance between the inner cone tip of the flame and the polymer have been investigated. Mild flame treatments were found to be effective in promoting the adhesion of polyurethane paints to the polypropylene. The adhesion between flame‐treated polypropylene and the paint film was assessed using a composite butt test and the measured bond strengths were found to be well in excess of those obtained using solvent wiping or chlorinated polyolefin primers.