Permeability of silo bag material for carbon dioxide and oxygen

Silo bag or grain bag storage system is a recently developed technology used for temporally storing dry cereal grains, oilseeds and pulses. The silo bag film is made of high and low density polyethylene. The success of this storage system depends on airtightness of silo bags, and permeability of the silo bag film is one of the main parameters that determines the airtightness of the silo bag. Permeability of the silo bag film to carbon dioxide (CO2) and oxygen (O2) has not been reported. The stretching of a silo bag during grain loading and storage time of grain (the silo bag film will be exposed to sunlight during storage period) may affect its permeability. Permeability to CO2 and O2 of the silo bag film was determined using a specially designed testing unit which had testing and receiving cells separated by the tested silo bag film. The gases were held in the testing (O2 or CO2 99.9% purity) and receiving cells (N2 99.9% purity) for 48 h; and about 1.5 ml gas samples were collected using a 2 ml syringe at 0, 4, 8, 12, 24, 48 h after purging from the receiving cells. The gas samples were analyzed using a gas chromatograph. The permeability of silo bag film at room temperature to CO2 and O2 were 21.61 ±1.50 ×10 -6, and 1.95 ±0.36 ×10-6 m3m d-1m-2atm-1 respectively. The permeability to CO2 and O2 was affected by the storage environment and stretching.