Additive migration from various plastics with different processing or properties into test fat HB 307.

The migration of the antioxidant n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate from various plastics into the test fat HB 307 was investigated. Plastics from the following classes were included: high-impact polystyrene (HIPS), polypropylene (PP), high- and low-density polyethylene (HDPE and LDPE), and were found to have distinctly different properties--in particular, different densities, melt flow indices and structural characteristics. Each plastic was processed into test specimens such as pressed and extruded sheets, injection-moulded cups, deep-drawn tubs and blown bottles. The migration out of these specimens was investigated under identical test conditions. The results confirm that the amounts of additive migrating from the different classes of plastics into test fat HB 307 in general decrease in the order LDPE greater than HDPE greater than PP greater than HIPS. Moreover, it seems to be of great importance that the respective amounts of additive migrating from the injection-moulded cups, deep-drawn tubs and blown bottles into test fat were significantly lower in all cases than those from the corresponding pressed or extruded sheets. Presumably, this effect is mainly caused by orientation of the polymer molecules in the injection-moulded, deep-drawn or blown products. It is concluded that the migration of the antioxidant decreases with increasing density of the polymer and that the melt flow index (molecular weight) has hardly any influence. Migration from HIPS into fat increases with the content of impact modifier. In the case of the polyethylenes, the influence of processing on the migration rate decreases with decreasing density of the polymer.