Gas transmission rates of unperforated and perforated polyethylene films for modified atmosphere packaging applications
2011
Malilay, I.X.R. | Yaptenco, K.F. | Elepaño, A.R. | Casas, E.V., Philippines Univ. Los Baños, College, Laguna (Philippines). Agricultural and Bio-Process Div.
Oxygen and carbon dioxide transmission rates (OTR and CO2TR, respectively) of low-density polyethylene (LDPE) films were measured at 5, 10 and 26 deg C (ambient condition) using an exponential decay method. Commercially available LDPE films with a nominal thickness of 25, 40, and 50 micro m were used, transmission rates of unperforated film samples were measured first, followed by measurements when samples were perforated once with 1.10 mm cold needle. Values for OTR and CO2TR of unperforated film samples decreased at lower temperatures and as film thickness increased. The effect of temperature followed Arrhenius kinetics (R20.920), activation energy (E sub a) for OTR and CO2TR had a range of 20.9-32.6 and 18.8-35.1 kJ/mol, respectively. Perforations made with a cold needle were roughly rectangular and had an average length, width, and area of 731 micro m, 71 micro m, and 51,695 sq micro m, respectively, corresponding diameter of a circular perforation with an equivalent area was 256 micro m which was considered as a macro-perforation. Gas transmission tests showed that as film thickness and temperature increased, OTR and CO2TR through individual perforations tended to decrease. The temperature effect could be due to distortions in the film at different temperatures. OTR and CO2TR per perforation had a range of 703-1, 146 and 337-896 mL/d, respectively. Calculations based on the respiration rate of 'Lakatan' banana at 28 deg C showed that a transport package of this banana variety (13 kg) could be kept at 28 deg C and 5% O2 using 38.1 micro m PE film without perforations. For bulk storage of 240 kg of the same variety, however, an impermeable plastic tent provided with perforated diffusion windows would require 64 perforations at 28 deg C to maintain the required level of O2.
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