Polyethylene terephthalate permeability

How do the polyvinyl alcohol platelets reduce gas permeability in polyethylene terephthalate soda bottles ... 

The above-mentioned method is effective in identifying the molecules of detected ions. However, because PVDF film is not permeable to light, it is difficult to observe tissue sections. To resolve this problem, we developed a method to fix tissue sections on transparent film, and then performed MS on those sections.6 We used a conductive film because we expected the ionization efficiency would increase when the electric charge accumulation on the sample was reduced. The film used for this purpose was a polyethylene terephthalate (PET) film with a thickness of 75-125 pm, having a 5 15-nm-thick layer of evaporated oxidation indium tin (ITO) upon it (ITO film). This film is used in touch-panel displays because of its high transparency and superior conductivity. We used it to perform MS/MS for tissue sections and succeeded in identifying multiple proteins from mass spectra.6 Therefore, the further development of this method will enable the application of the mass-microscopic method to observe tissue by optical microscope and to perform tandem mass spectrometry (MSn) at the observation part, simultaneously, enabling the identification of molecules included the part. 

Polyethylene terephthalate) (PET), with an oxygen permeability of 8 iiiuol/(ius-GPa), is not considered a barrier polymer by die old definition however, it is an adequate barrier polymer for holding carbon dioxide in a 2-L bottle for carbonated soft drinks. The solubility coefficients for carbon dioxide are much larger than for oxygen. For the case of the PET soft drink bottle, the principal mechanism for loss of carbon dioxide is by sorption in the bottle walls as 500 kPa (5 atm) of carbon dioxide equilibrates with the polymer. For an average wall thickness of 370 pm (14.5 mil) and a permeabdity of 40 nmol/(m-s-GPa), many months are required to lose enough carbon dioxide (15% of initial) to be objectionable. 

The recent trend towards polyethylene terephthalate (PET) packaging presents its own problems. Typically PET containers cannot be hot filled around 50°C is the upper temperature, although some recent types can be heated to 85°C. They are also permeable to oxygen (Rodriguez el al., 1992), which allows the growth of aerobic spoilage agents. 

Barrier Plastics. When plastics replace metals and glass in packaging, their permeability is often a limiting property. Barrier performance generally increases with density and crystallinity. The most promising barrier plastics include ethylene/vinyl alcohol, polyvinylidene chloride, polyacrylonitrile, and polyethylene naphthoate. These are used most efficiently by laminating them to commodity plastics such as polyethylene and polyethylene terephthalate. 

Hill, A.J., Winhold, S Stack, G.M., Tant, M.R. (1996) Effect of copolymer composition on free volume and gas permeability in polyethylene terephthalate) -poly(l,4 cyclohexylenedimethylene terephthalate) copolymers . Eur. Polym. J. 32(7), 843. 

Fig. 15. Oxygen permeability versus 1/specific free volume at 25 °C (30). 1. Polybutadiene 2. polyethylene (density 0.922) 3. polycarbonate 4. polystyrene 5. styrene-co acrylonitrile 6. polyethylene terephthalate) 7. acrylonitrile barrier polymer 8. poly(methyl methacrylate) 9. poly(vinyl chloride) 10. acrylonitrile barrier polymer 11. vinylidene chloride copolymer 12. polymethacrylonitrile and 13. polyacrylonitrile. See Table 1 for unit conversions.

Solubility of CO2 at 25 °C in polyethylene terephthalate vs. the gas pressure (from Hopfenberg H. B., Ed., Permeability of Plastic Films and Coatings, Plenum Press, 1974). 

Figure 11.26 A schematic diagram of an apparatus used to obtain estimates of the passive permeability of a drug candidate across the intestinal mucosa using Caco-2 cells. A monolayer of Caco-2 cells is grown on a porous polyethylene terephthalate (PET) membrane (a so-called confluent monolayer of cells that grows only in two dimensions on such a substrate from an initial small inoculation). In the experiment the cells are submerged in Hanks s Balanced Salt Solution (HBSS) buffer (contains Na+, K+, CP, phosphate, glucose, and in some formulations also Ca +, Mg + and S04 ) the Caco-2 cell layer provides the only connection between an apical (donor) reservoir, into which the drug candidate is dosed, and a basolateral (receiver) reservoir. For the assay, aliquots are removed for analysis from the apical reservoir at Omin, and from both reservoirs at 120 min. Reproduced from Van Pelt, Rapid Commun. Mass Spectrom. 17, 1573 (2003), with permission of John Wiley Sons Ltd.

PHA solutions of various densities were used to prepare transparent flexible films. The surface properties of PHB and P(HB-co-HV) fllm scaffolds were similar to each other and to those of synthetic polyesters (polyethylene terephthalate, poly (methyl methacrylate), polyvinyl chloride, and polyethylene) (Shishatskaya 2(X)7X The scaffold s surface properties are important for cell attachment and proliferation. To enhance cell adhesion to the surface, improve the gas-dynamic properties of scaffolds, and increase their permeability for substrates and cell metabolites, the scaffolds can be treated by physical factors or by chemical reagents. Biocompatibility of PHA scaffolds has been enhanced by immobilizing collagen fllm matrices on the scaffold surface and coating with chitosan and chitosan/polysaccharides (Hu et al. 2003). 

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