Poly food contact materials

Both thermosets and thermoplastics are used as food-contact materials, though thermoplastics predominate in this appfication. Examples of the former are phenol- and urea-formaldehyde, while probably the best known example of the latter is low-density poly(ethylene). Other linear polymers are used include high-density poly(ethylene), poly(propylene), and PVC, all of which find quite extensive use. Polymers for food packaging may be in the form of films and other flexible items, or in the form of rigid containers, such as clear drinks bottles or opaque cartons for dairy products. 

Case study Poly EthyleneTerephthalate (PET) as a food contact material... 

The commercial polymeric films (Table I) that are used as the outside layer of multilayered materials for thermoprocessed food packaging are poly(ethylene terephthalate), polyiminocaproyl, or polypropylene. The other five films listed in Table I or polypropylene are used for the food-contacting layer. 

Bond strength data for four multilayered materials is shown in Table V. In each case the data is for the bond between the food-contacting layer and its adjacent layer. In Pouch 1, it is the bond between ethylene-butene copolymer and aluminum foil in Pouch 2 between ethylene-butene copolymer—polyisobutylene blend and aluminum foil in Pouch 3 between ethylene-butene copolymer and polyiminocaproyl and in Pouch 4 between ethylene-butene copolymer and poly(ethylene terephthalate). Bond strength increased in the four multilayered materials after the irradiation treatment. 

The resulting poly(oxy-1,4-phenylene sulfonyl-1,4-phenylene) (PES), CAS 25667-42-9, is a valuable polymer used to make various household appliances, medical devices, automotive parts, etc. The polymer can be shaped by thermoforming and is used in various composite materials. It has good fire safety characteristics and meets the requirements for direct food contact. Other polyethersulfones with structures similar to PES also have important practical applications and are used for the manufacturing of different appliances, cookware, automotive and aerospace components, etc. 

Once the plastic has been separated into its various types, it can be recycled by reprocessing. More commonly, some recycled polymer is added to virgin polymer, although this may limit the application of the resulting material. For example, poly(vinyl chloride) containing 25% recycled resin is available, but only for applications in which it does not come into contact with food. 

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