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Abstract
Low-density polyethylene (LDPE)/polypropylene (PP) blend films in various blending ratios containing 3000 mg kg−1 of tocopherol were manufactured by an extrusion process. Tocopherol release properties were characterised and correlated with antioxidant effectiveness in retarding the oxidation of linoleic acid contacting the films at 40°C. The conditions without tocopherol (control) and with instant tocopherol addition corresponding to the amount included in the films were also prepared and compared with the film-contacting solutions. The effect of tocopherol inclusion and the blending ratio on their physical properties was also examined. A wide range of tocopherol diffusivity in 6.6 × 10−16–4.6 × 10−14 m2 s−1 were obtained by blend films. As PP content increases, the diffusivity decreased sharply at the beginning and levelled off later. The slower release of tocopherol in LDPE/PP blend films corresponding to lower tocopherol diffusivity retained the higher tocopherol concentration in the linoleic acid system providing better antioxidant effectiveness of the extended induction period in oxidation. The tocopherol inclusion reduced tensile strength and transparency significantly in an affordable range with higher tensile strength given by a higher PP ratio. LDPE/PP blending can be a useful tool to modulate the release profile of tocopherol and thus the antioxidant effectiveness of the tocopherol-incorporated antioxidant packaging film.
Acknowledgements
The authors thank Berry Plastics Corporation for film production and for financial support.