Permeability Total package

In practice it must not be forgotten that P values give an order of magnitude estimation for the selection of suitable packaging materials and thus allow a closer calculation of the total package permeability with the help of the flux J ... 

With this setup, non-destructive testing of the total package permeability can also be carried out. Using the results obtained for C02, the total permeability for other gases can be estimated with the help of Table 9-3. 

The permeability of a material can vary widely at different locations in the package. Different material thickness of the walls, bottoms, edges and seals, different materials for lid and container or the presence of pores or other leaks for example can all cause considerable differences between the calculated and total effective permeability of a package. 

Q is the sum of the permeabilities for individual packaging materials and wall thickness of different packaging components. Using the corresponding P and d values for every component i, the corresponding flux J is calculated using Equation (9-1) and multiplied by the component s surface Aj. The partial pressure difference Ap is treated as a constant. The total permeability of a package developed in this way must nevertheless be checked experimentally due to the above mentioned uncertainties (see next Section). 

A precondition for the optimization of a package having a specified minimum shelf life date for a food with a known oxygen and/or water sensitivity is the calculation of the permeability of laminate structures. The total permeability Qv of a laminate film made from n different plastic layers with thicknesses d, and having permeability coefficients of Pj can be calculated using the following formula ... 

Films. Three films were included in this study. Low density polyethylene (LDPE) was included as a representative polyolefin. It is not considered to be a barrier polymer. It has permeabilities to selected aroma compounds slightly higher than the permeabilities of polypropylene and high density polyethylene (1). A vinylidene chloride copolymer (co-VDC) film was included as an example of a barrier that is useful in both dry and humid conditions. The film was made from a Dow resin which has been designed for rigid packaging applications. A hydrolyzed ethylene-vinylacetate copolymer (EVOH) film was included as an example of a barrier film that is humidity sensitive. The polymer was a blend of resins with total composition of 38 mole% ethylene. 

In the Longevity process, the UHMWPE bars are warmed, placed in a carrier on a conveyor, and are exposed to electron beam radiation, with a total dose of 100 kGy. The UHMWPE does not heat above the melt transition during the crosslinking. After irradiation, the UHMWPE is heated above the melt temperature (>135°C) for stabilization of free radicals. Components are then machined from the Longevity material, enclosed in gas-permeable packaging, and sterilized by gas plasma. 

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).

XLK is based on technology developed for Marathon (see Section 20.8). XLK was clinically introduced for the PFC Sigma total knee component systems in 2005. The XLK process is the same as previously described Marathon except that ram extruded GUR 1020 is used for XLK (instead of GUR 1050 used for Marathon). Components are machined from processed XLK material, enclosed in gas-permeable packaging, and sterilized by gas plasma. XLK is available in the PFC Sigma knee system in PLI, Curved, Curved+, and Stabilized inserts (Figure 20.9). 

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