A critical issue in food packaging is that of migration and permeability : no material is completely impermeable to atmospheric gasses, water vapor, or natural substances contained within the food being packaged or even the packaging material itself.
As a result of these complexities, food products require sophisticated and remarkably different packaging functions, and the demands on the packaging industry will only increase as food is transported over increasingly longer distances between producers and consumers.
Traditional materials for food packaging include metal, ceramic (glass), and paper (cardboard).
While these materials are still used, the light weight, low cost, ease of processing and formability, and remarkable diversity in physical properties of organic polymeric materials makes plastics attractive alternatives for the packaging of foods.
Polymers which are most frequently used for food packaging include, but are not limited to, polyolefins such as polypropylene (PP) and various grades of polyethylene (HDPE, LDPE, etc.), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC).
Though polymers have revolutionized the food industry and possess numerous advantages over conventional materials, their major drawback is an inherent permeability to gasses and other small molecules. Some polymers are better than others in this regard.