Barriers against the Migration of Mineral Oil from Paperboard Food Packaging: Experimental Determination of Breakthrough Periods

A method is described for determining the breakthrough periods through various types of potential functional barriers. A donor pack with a sheet of paper containing the test migrant(s) was tightly fixed to one side of the barrier. It included a blank sheet of paper as a spacer to rule out wetting contact between the donor and the barrier. A polyethylene film acted as a receptor on the other side. Periodically, a piece of the receptor film was analysed for the test migrants broken through the barrier. As benchmarks, periods were extrapolated for 1% and 10% breakthrough compared with equilibration. Tests were performed at 60°C, 40°C and ambient temperature. Acceleration by increased temperature gave reasonably adequate results for polyethylene but too short breakthrough periods for polypropylene, owing to structural changes in the polymer. The donor pack also included Sudan red 2, which is of sufficient volatility to migrate through the gas phase. It enabled visual control for gaps and holes in the barrier layers or cracks, e.g. from manipulation (such as bends or scratches), by red spots in the tested material behind the barrier or in the receptor film. Breakthrough data for mineral oil of the type typically used in cold-set offset printing inks are provided for a selection of materials. Polyethylene terephthalate and polyamide showed no breakthrough for a period corresponding to 6.9 years. Copyright © 2011 John Wiley & Sons, Ltd.