Saran packaging material

Saran (Dow polyvinylidene dichloride) is a tough, chemically resistant plastic available in a variety of forms that are useful in the laboratory. Saran pipe or tubing can easily be welded to itself or sealed to glass and is useful for handling corrosive solutions. Thin Saran film, available commercially as a packaging material, is useful for windows, support films, etc. Mylar (du Pont polyethylene terephthalate) film and other polyester films are also useful for these purposes. Mylar is chemically inert and has excellent electrical properties for electrical insulation and for use as a dielectric medium in capacitors. Much thinner than these are films that can be made in the laboratory by allowing a dilute ethylene dichloride solution of Formvar (polyvinyl acetal) to spread on a water surface and dry. 

Dow s Satan wrap, which is a copolymer of vinyhdene chloride and vinyl chloride, is a usefiil packaging material that possesses exceptional clarity, toughness, and impermeability to water and gases. Also available from Dow is a range of Saran resin and films with improved barrier properties. For example, Saran HB monolayer lamination films are claimed to exhibit an oxygen barrier 10 times greater than the conventional Saran wrap films. 

Poly(vinylidene chloride) (PVDC). The homopolymer is intractable in the conventional plastics processing techniques. For this reason, copolymers of vinylydene chloride with vinyl chloride or terpolymers with vinyl chloride and acrylonitrile are used. Due to its exceptionally low vapour, gas, and aroma permeability, PVDC films are used for packaging and for the barrier layer in composite films. Paper varnished by PVDC is a widespread packaging material. Trade names Diofan (FRG), Ixan (B), Saran (USA). 

Saran plastic shows the lowest permeability to O2, CO2, and very low for water. This feature makes Saran wrap an excellent packaging material for food in which freshness and flavor are to be preserved. 

Isotope dilution GC-MS (IDGC-MS) procedures have been used for the evaluation of the migration of plasticisers from packaging materials (PE, PVC, cellulose and vinylidene chloride films) into foods [77-79]. Acetyltributyl citrate (ATBC) migration from Saran (vinylidene chloride-ct>-vinyl chloride) has been measured by means of IR spectroscopy, extraction/saponification [80] and stable isotope dilution GC-MS using [ Hs] ATBC [79]. 

Skin packaging employs material properties which are similar to stretch wrapping in that the film employed may stretch in the process. However, heat and vacuum are usually employed, hence stretch may also approach an orientation operation. In terms of material, Surlyn ionomer and Saran may be used as well as the more conventional materials. 

Polyvinyl chloride (PVC) is an economical thermoplastic film with good barrier properties to gases and water. Later developments of even higher barrier Saran type resins based on copolymers of vinylidene chloride and vinyl chloride produced many new packaging opportunities. These materials are still very popular today (37-39). Consideration of the structure-permeability relationships for the Saran materials in Chapter 6(40) indicates that their evolution is still continuing as better understanding of the influence of sequence distribution and even more subtle issues of chain microstructure emerge. 

There are two polymers used in a maj ority ofhigh barrier food packages copolymers containing polyvinylidene chloride (Saran ) and ethylene-vinyl alcohol copolymer (Eval, Selar-OH ). Packages in which either polyvinylidene chloride or ethylene-vinyl alcohol copolymer (EvOH) provide the barrier are invariably multilayer since neither of these materials offers the properties required to make a good monolayer structure. There are advantages and disadvantages associated with each of these materials, and the... 

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