SORPTION OF FATTY-ACIDS INTO LOW-DENSITY POLYETHYLENE AND ITS EFFECT ON ADHESION WITH ALUMINUM FOIL IN LAMINATED PACKAGING MATERIAL

Unsaturated fatty acids dispersed in water/SLS/ethanol (87/3/10) were stored in laminated packaging material at room temperature for 4 weeks (study A). Monounsaturated fatty acids were sorbed 2-4 times better t han polyunsaturated ones and resulted in LDPE/Al foil delamination alr eady within 2 days. Polyunsaturated acids were less uniformly sorbed b ut caused a severe decrease in interlayer adhesion, followed by an inc rease up to 50-60% of initial adhesion. In a second study (study B) th e effect of chain length was investigated by dissolving fatty acids in 95% ethanol. The sorption rate of this fatty acid series increased wi th increasing chain length. The interlayer adhesion decreased to about half of the initial adhesion in 1 week and stayed at that level throu ghout the study. It appeared that the rate of delamination was not dir ectly proportional to the amount of sorbed fatty acid.