Effect of cut edge area on the migration of BHT from polypropylene film into a food simulant

Abstract

The effect of edge area on the migration of small molecules from polymer films is seldom addressed. This study evaluated the effect of edge area, especially the edge-to-face ratio (E:F), of a polypropylene (PP) film on the migration of butylated hydroxytolune (BHT) from the film into a food simulant. The PP-BHT film was selected as a model system since it had been widely studied. A two-sided contact migration test was performed on PP-BHT films exposed to ethanol at 40 °C. The film samples were divided into two groups: all samples had the same thickness, weight, and face area but each group had a different edge area. The diffusion coefficient of BHT migration was (0.5062 ± 0.0115) × 10−10 cm2 s−1 for the PP film samples with less edge area and (0.5319 ± 0.0112) × 10−10 cm2 s−1 for the PP film samples with more edge area. The diffusion coefficient for film samples with the edge not in contact with the solvent (to simulate the one-sided contact migration test) was also extrapolated and the result was (0.4920 ± 0.0114) × 10−10 cm2 s−1. The three diffusion coefficient values were not significantly different (P > 0.05), indicating no obvious effect of the cut edge area on migration. This statement was valid when the ratio of film edge area (E) to face area (F) was small, or below 0.056. However, as E:F increased, a slight increase in diffusion coefficient was observed, which could result in an overestimation of the migration level. Therefore, the E:F should be taken into account in the design of two-sided contact migration tests to minimize the potential impact of the cut edge area.