O_2-Durchlaessigkeit von Kunststoffflaschen und Verschluessen: Messung und Modellierung der Stofftransportvorgaenge

Oxygen influences the flavour stability of bottled drinks. Packaging materials consisting of metal or glass are impermeable for gases such as oxygen or carbon dioxide. Plastic packaging materials are permeable due to a pressure drop between the inner side and the outer side of the packaging materials. The author compares different bottle systems and stopper systems of oxygen sensitive drinks with respect to the properties of the gas barriere. Only a few exact analytical solutions exist with respect to the permeation of gases in plastic bottles and closures. Numerical solution processes such as finite difference method or the finite element method are necessary. These procedures need the knowledge of mass parameters describing the permeation, mass transfer and reaction kinetics. The author presents a measurement of these parameters. Furthermore, models are developed which describe the entry of oxygen and the simultaneous consumption by the substances inside the bottle. the measurement of the permeability of oxygen in bottles and closures is carried out according to DIN 53380 part 3 with an oxygen specific carrier gas process. Beside this process, a fiber optical sensor is used to determine the mass transfer coefficients. The fibre optical sensor is not suitable for long-term measurements. The activation of scavengers is measured with the aid of the carrier gas process, gas chromatography and gravimetrically. The carrier gas process is suitable to questions concerning the residual permeation in bottles and closures with an integrated scavenger, while the sorption capacity of oxygen can be determined by gas chromatography and gravimetry. The solubility coefficient, diffusion coefficient and permeation coefficient of oxygen in PET bottles can be determined by the layer thickness distribution and permeability of oxygen in the instationary area. The influence of the boundary layer between the plastics and the filling material decreases with increasing oxygen barriere efficiency of the bottle material. This influence is negligible in the case of PET, PEN, multilayer or coated bottles. Bottles made of pure PET are unsuitable for oxygen sensitive filing materials like bear due to a permeability of 40 mug oxygen per day. The use of barriere plastics reduces the permeability of oxygen by a factor of 10. The stationary state can be described well using the resulting analytical solutions of the differential equation for the one-dimensional case. In the case of barriere plastics, the instationary phases are not negligible. If oxygen scavengers are used, the problem of the instationary diffusion only can be solved by numerical solution processes such as finite difference method or finite element method.SIGLEAvailable from: http://tumb1.biblio.tu-muenchen.de/publ/diss/ww/2003/mueller.pdf / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman