Oxygen and Water Permeability

TABLE 8.2 Selected Barrier Properties of Common Plastic Packaging Films (25 pm Thick) Measured at 38 C 

Polymer Oxygen transmission rate (OTR) at 25°C and 0% RH (cmVmVday) Water vapor permeability at 38°C and 90% RH (g/mVday) 

70 30 mixture of and seafood including white fish in 30 40 30 mix of 02 C02 N2 (Air Products 

TABLE 8.3 Some Examples of Multilayer Eilms Used in Eood Packaging 

Deli meat casing LLDPE/o-nylon/PVDC 70/20/10 50-80 

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Biocompatible contact lenses having high oxygen and water permeability were prepared by Nicolson [5] by reacting the polysiloxane macromonomer, (III), with ethylene glycol, and 2% 2-hydroxyethyl methacrylate. 

Styrenic TPEs are the most widely used. One such material, commercialized by BASE in 1999, is a styrene-butadiene block copolymer with a styrene content of about 70%, intended for thin film for food packaging. It has high oxygen and water permeability, and excellent toughness and optical properties. Cling films with EVA layers on the outside are also available, which provide complete recovery of deformation at elongations up to 400%, and elongation at break of over 650%. 

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).

In the closure of an open pit, confinement of the environmentally unstable material, such as pyrite or radioactive materials can be achieved by storage below the water table (Fig. 6). For example at the Wismut uranium mine in Germany radioactive and sulphide-rich waste is stored below the water table preventing extensive further breakdown. Above this is a buffer zone and low-level waste and a clay barrier which acts to reduce oxygen and water permeability and also absorb any radium emission (Chapman Hockley 1996 Hockley et al. 1997). 

The primary function of a coating is to act as a barrier which isolates the underlying metal from the environment, and in certain circumstances such as an impervious continuous vitreous enamel on steel, this could be regarded as thermodynamic control. However, whereas a thick bituminous coating will act in the same way as n vitreous enamel, paint coatings are normally permeable to oxygen and water and in the case of an inhibitive primer (red lead, zinc chromate) anodic control will be significant, whilst the converse applies to a zinc-rich primer that will provide cathodic control to the substrate. 

To apply these package criteria to polymer properties, a conversion was made based on a 10-12 oz. container with a surface area-to-volume ratio of 4.0 (in.2/oz.) and an average wall thickness of 0.030 in. The oxygen, carbon dioxide, and water permeability rates needed to meet these high barrier criteria over a six month shelf life are shown in Table III. Larger container sizes—16, 32, 48 oz. etc.—would permit slightly higher permeability factors for the same bottle criteria, because of their lower ratio of surface-to-volume. 

Multilayered materials owe their properties and behavior to the properties of and the interactions between the components (5). Each of the two or more components contributes its particular property to the total performance of the multilayered material. For example, in Pouch 1, Table II, the aluminum foil provides high oxygen and water vapor permeability resistance, poly (ethylene terephthalate) provides structural strength and stiffness, and the ethylene-butene copolymer provides a heat sealable layer. If the components of the multilayered materials interact then the whole would be something different than the sum of its parts. In other words, the properties of the components of the multilayered materials are not independent of one another but rather are interdependent. 

Table I. Oxygen and water vapour permeabilities (P02 PH2O) with mean deviation (m.d.), water solubility (S1J20) and diffusion coefficient (Djj o) at 21°C.

If the aim of excipient compatibility is to be predictive of the degradation expected with clinical or commercial dosage forms, then the packaging configuration should be representative of what will be used in that setting. Factors that could influence stability measurements include container headspace and permeability of oxygen and water vapor through the walls and cap (if a bottle) of the container. 

For example, consider a soft drink or soda bottle. What are the requirements Cheap Strong enough to contain up to 2L of soda. Optically clear. And very important, a barrier for 0O2, because carbonated beverages taste flat once the concentration of carbon dioxide falls too low. Table 8-1 lists the permeability of various polymers to C02 as well as to oxygen and water vapor. 

In 2004, Treofan GmbH developed a metallised version of its PLA biodegradable film that reduces permeability aromas, oxygen and water. The metallised Biophan PLA film is said to be suitable for packaging fatty foods such as butter and cheese, as well as for confectionery, where the mirror-like finish adds a decorative feature to the barrier properties. The metallised film meets both EU and US, Food Drug Administration food contact requirements. 

DEHA is used in preference to phthalates due to improved flexibility at lower temperatures and also gives the necessary permeability to oxygen and water vapour to preserve the freshness of the food. 

The permeability of the polymer to oxygen should be <1.0 cm -mil 100 in. day atm . Diffusion of oxygen and water through the polymer to the microelectronic circuitry could cause corrosion and is thus undesirable. To establish a value for this physical property constraint, we examined polymers used as barriers. Polymers with a permeability to oxygen of <1.0 cm -mil 100 in. day atm are considered high-barrier materials. 

The possibility of using flexible substrates to fabricate fully flexible displays is particularly attractive (see Fig. 4.2). The critical limitation of the flexible LED technology is the permeability of most plastics to oxygen and water vapor. This permeability allows atmospheric oxygen and water vapor into the device and accelerates degradation. Water vapor is especially hazardous to the device operation since it will react with the low work function cathode. The development of technology... 

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