Polystyrene barrier properties

Because of the excellent gas barrier properties, EVOH is of interest as a packaging material. However, because of its high water absorption it is usually used as an internal layer in a co-extruded film, sheet, bottle or tube. For example, the system HDPE-EVOH-EVA may be used as a barrier film for packaging cereals, and the system polystyrene-EVOH-polystyrene for packaging coffee and cream, whilst the system polystyrene-EVOH-polyethylene has the additional advantage of heat scalability. 

Many thermoplastics can be thermoformed, including polystyrene, polypropylene, APET, CPET, and PVC. EVOH is commonly incorporated into a co-extrusion for its superior barrier properties in food. Co-extrusions of these materials are commonly used to provide precise properties for specific applications. 

Because PLA finds a lot of applications in food packaging, its barrier properties (mainly to carbon dioxide, oxygen and water vapour) have been largely investigated [4]. The CO2 permeability coefficients for PLA polymers are lower than those reported for crystalline polystyrene at 25°C and 0 per cent relative humidity (RH) and higher than... 

PS is a stiff, brittle material with relatively poor barrier properties. Crystal PS has excellent transparency. In its foamed form, PS has very good cushioning abilities, as well as insulation properties. Cost is relatively low, especially in molded expanded polystyrene (EPS) and extruded foam PS, where a small amount of mass can yield a large volume. PS is readily shaped by injection molding, extrusion, or thermoforming, in either foamed or unfoamed form. 

Figure 8.6 Barrier properties of commercial PHA resins compared to other bio- and oil-based polymers used for packaging, as measured by oxygen and water permeabilities, (PS1540 Polystyrene from Arkema PP7712 Polypropylene from Total Chemical Company PLA7001D Poly(lactic acid) from Natureworks P228 PHA from Biomer MirelF1006 3002 PHA from Metabolix Enmal YIOOOP PHA from Tianin Biologic PA MXD6 PHA from Mitsubishi Chemical Company).

Dai G, Mishnaevsky Jr L (2013) Damage evolution in nanoclay-reinforced polymers a three-dimensional computational smdy. Compos Sci Technol 74 67—77 Durmus A, Woo M, Kas goz A, Macosko CW, Tsapatsis M (2007) htbnealated linear low density polyethylene (LLDPE)/clay nanocomposites prepared with oxidized polyethylene as a new type compatibilizer stmctural, mcehanieal and barrier properties. Eur Polym J 43 3737—3749 Pan J, Liu S, Chen G, Qi Z (2002) SEM study of polystyrene/clay nanocomposite. J Appl Polym Sci 83 66-69... 

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