The effect of b-carotene on the behaviour of polyethylene stabilised with a-tocopherol and a phosphonite
antioxidant was studied under processing and storage conditions. The amount of b-carotene ranged
between 0 and 2000 ppm. The polymer was characterised by different methods after processing then
during and after storage at ambient temperature in light and dark. b-Carotene hinders the oxidation of
polyethylene and does not increase the chain extension reactions during processing, though more vinyl
groups and phosphonite molecules react. b-Carotene colours polyethylene strongly already at low concentrations. The reactions of the polymer and b-carotene are affected strongly by the storage conditions.
The presence of b-carotene does not influence the stabilising efficiency of the primary and secondary
antioxidants. In dark the molecular structure of the polymer does not change appreciably, while the
reactions of b-carotene lead to an increase in the yellowness index. In light the molecular characteristics
of polyethylene undergo significant changes indicating long chain branching. The polymer fades rapidly
after an induction period. The length of the induction period is not influenced by light. The rate of the
degradation reactions of b-carotene during storage is controlled by its concentration and film thickness.
Visible autoaccelerated decomposition in light renders b-carotene candidate as an indicator in active
packaging materials.