Cling film is a clear, flexible product used in food packaging that clings to food containers and itself. It keeps food fresh and prevents food dehydration. Cling film is made of synthetic polymers, which are large chains of small molecules. The production of household cling film uses three kinds of polymers, each with its own properties. The use of cling film has raised environmental concerns.
Imperial Chemical Industries of Britain discovered polythene in 1933, by mixing ethylene and benzene at a high temperature and pressure. Visking Corporation in the United States first made it into a film in 1945. Polythene evolved into two forms: low-density polythene, or LDPE, and high-density polythene, or HDPE. LDPE is used in the production of cling film and it tends to be impermeable and naturally flexible, but it does not cling well.
Polyvinyl Chloride or PVC was produced before World War II. Its first use was as a rubber substitute. It is made with either vinyl chloride or acetylene. In its normal form, it is rigid, but PVC wrap is chemically softened using a plasticiser known as phthalates. Polyvinyl chloride wrap clings well to dishes and itself, but it is not impermeable.
Dow Chemical Company developed Polyvinylidene chloride, or PVDC, during World War II for military use. In 1952, it was produced for the public under the name Saran Wrap. Saran Wrap was the first cling wrap designed for household use. This wrap is made from vinyl chloride and vinylidene chloride, and requires a plasticiser to soften it. PVDC wrap resists oxygen, water, bases, acids and solvents.
Cling film is a single use petroleum-based product. It contributes to household waste because it is not recycled, and rarely reused. Concerns also exist about plasticisers used to soften plastics for wrap. The chemicals are absorbed into hot and fatty foods. PVC wrap is composed of as much as one-third plasticisers, and PVDC wrap uses about 10 per cent plasticisers. Polythene wrap does not use plasticisers. Alternatives to cling film include aluminium foil and reusable containers.