Effects of flame treatment on propylene–ethylene copolymer surfaces

Abstract

AbstractThe effects of flame treatment on the surfaces of a propylene‐ethylene copolymer have been studied using XPS, contact angle measurement, vapour‐phase derivatization and an adhesion test. The results obtained were compared to those from the homopolymer. An optimum air‐to‐gas ratios of ∼11:1 has been found. Close correspondence between water contact angle and oxygen concentration was found, with the exception of high oxygen concentrations. The orientation or migration of functional groups away from the surface has been proposed to cause the non‐correspondence between water contact angle and oxygen concentration. Diiodomethane advancing contact angle was found to remain constant, independent of flame conditions. XPS analysis in conjunction with vapourphase derivatization with trifluroacetic anhydride (TFAA) suggests that up to 20% and 30% of the oxygen introduced in the surfaces is present as hydroxyl groups for propylene homopolymer and the copolymer, respectively. High adhesion levels of the flame‐treated copolymer with a polyurethane‐based paint were found. In most cases, the adhesion failure was complex, but involved the cohesive failure of the copolymer.