Surface modification studies of Kapton®HN polyimide films

Surface imide hydrolysis of Kapton HN polyimide films in a 1 M KOH aqueous solution was studied using dynamic contact angle measurements, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The surface energy of Kapton HN increased quickly upon KOH treatment due to the formation of polar polyamate. Prolonged treatment led to a jump in surface energy that we ascribe to the onset of etching causing increased surface roughness. Potassium depth profiles of treated Kapton HN samples measured by XPS and TOF-SIMS demonstrated that during the first 10 minutes of 1 M KOH treatment the modification depth increased rapidly. Thereafter the thickness of the modified layer no longer increased. For Kapton H films, however, the development of etching was much slower and a steady increase in modification depth was observed even after long treatment times. The different behaviours between Kapton HN and Kapton H films in alkali solutions are analysed and discussed. Copyright © 2003 Society of Chemical Industry