Measurement of carbon dioxide diffusion across plastic films using exponential decay method
2002
de Ramos, J.D. (Philippines Univ. Los Banos, College, Laguna (Philippines). Coll. of Engineering and Agro-Industrial Technology) Serrano, E.P.
Fruits, vegetables and flowers still respire after harvest, thus, using up oxygen and giving off carbon dioxide. Keeping them in plastic bags or tents slows down this process, thus, delaying ripening or deterioration as well as minimizing moisture loss. This technique is called modified atmosphere (MA) packaging or storage. Ideally, to get the most from MA packaging or MA storage, a steady state or equilibrium concentrations of oxygen and carbon dioxide should correspond to the concentration of these gases required by the commodity to last long in storage. At steady-state condition, the amount of gas that gets inside the bag is equivalent to the amount that leaves the bag. Too much carbon dioxide or too little oxygen may injure the commodity. Gases can pass through plastic films, which bags or tents are made of. Their transmission rate coefficient (the rate at which they pass across a plastic film) can be used to predict the time in which gases inside an MA package will attain steady-state condition. In turn, the information can be used to determine whether or not a plastic film is suitable for MA storage of a perishable crop. In this study, a chamber was fabricated to determine the transmission rate coefficients of carbon dioxide across polyethylene (PE) films of varying thickness using a mathematical program called the exponential decay method. Time needed to attain steady-state condition was also determined. The results showed that transmission rates of carbon-dioxide across PE films that are 0.051 millimeter and 0.025 millimeter thick were the same. It took 140 hours, however, for the thicker film and 100 hours for the thinner film to attain a steady state
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