EFFECTS OF DIFFERENT ORGANIC-ACIDS ON THE ADHESION BETWEEN POLYETHYLENE FILM AND ALUMINUM FOIL

The effect of organic acids on the adhesion between the polyethylene l ayer and the aluminium foil in laminated food packaging material was s tudied after test packaging. A 3% (wt/wt) solution of acetic acid and equivalent solutions of propionic acid, citric acid and lactic acid we re packed in envelopes consisting of: LDPE/paper/LDPE/Al foil/LDPE and stored at room temperature for 4 weeks. As previously reported, aceti c acid caused a total delamination within a few days followed by a rec overy back to 50% of the initial value after 2 weeks. The material sto red in propionic acid showed a total delamination of LDPE and aluminiu m after 8 days of storage and remained at this level during the rest o f the observing period. FR-IR scans and ESCA analysis showed a formati on of a salt for both acetic acid and propionic acid. The package mate rial in contact with citric acid, lactic acid and water did not show a ny marked change in adhesion or salt layer formation during the storag e time.