Many additives are commercially used to add more favorable qualities to films. The bleeding process by which the additive in a film comes to the surface is considered. A new bleeding model of additives in a polypropylene film under atmospheric pressure was investigated. Solubility and diffusion are found to be important for explaining this bleeding process. The solubilities and diffusion coefficients of higher fatty acid amides such as erucamide (13-cis-docosenamide) and behenamide (docosanamide) were determined between 40 and 70 degrees C and the difference between the solubilities and the diffusion coefficients was discussed. The experimental results are explained more precisely by assuming two transport processes between the crystalline regions and the amorphous ones. (c) 2007 Wiley Periodicals, Inc.