| Popis: |
Nine types of polyethylene films for modified atmosphere packaging (MAP) from three suppliers were evaluated for O2, CO2, and H2O vapor transmission rates (OTR, CO2TR, WVTR, respectively) at four temperatures (0.0, 5.0, 15.5, and 23.2°C). Experimentally measured and quoted OTR were compared and differences of 16.7% were obtained for supplier A, 30.8% for supplier B, and 74.2% for supplier C. Bag-to-bag consistency was best for supplier A followed by B and then C. Measurements on similar films supplied in a different year showed good batch-to-batch uniformity. The average ratio of CO2TR/OTR decreased from 5.93 to 5.26 as temperature increased from 0 to 23.2°C, while the average ratio of H2O permeance/O2 permeance (on molar bases) decreased from 80.7 to 47.0. Arrhenius activation energies (kcal/mole K) averaged 8.73 for O2, 7.77 for CO2, and 6.22 for H2O vapor. An increase in temperature from 0 to 23.2°C affected OTR the most (compared to its 0°C value), followed by a slightly smaller effect on CO2TR (87% of the effect on OTR), and by a considerably smaller effect on H2O permeance (69% of the effect on OTR). |
