Study of diffusion through LDPE film of Di-n-butyl phthalate

The apparent diffusion coefficients (D) across a PE-LD film of Di-n-butyl p hthalate (DnBP) dissolved in isooctane and ethanol, were calculated in diff erent ways and compared. DnBP, a common plasticizer of plastics and printin g inks, may be a possible contaminant of flexible packaging and PE-LD is th e most common food-contacting polymer. To perform diffusion measurements, s mall plastic sachets filled with solutions of the contaminant were used at three different temperatures. The D coefficients of the two solvents and di ssolved DnBP were calculated using the lag time method, a formula taking in to account the molar weight and absolute temperature, and an equation based on the initial concentration and the amounts migrated after subsequent tim es. The results demonstrated great solvent interference in the plasticizer diffusion across polyethylene; in particular as far as isooctane is concern ed, a remarkable co-diffusion of both the plasticizer. and the non-polar so lvent must be assumed. Isooctane quickly penetrates PE-LD but ethanol also diffuses across PE-LD, although at a greatly reduced speed. These facts mus t be considered for realistic predict ion of migration or effectiveness of the functional barrier.