Temperature effect on H2S diffusion through nalophan™

The Hydrogen sulphide (H2S) loss, an odorous molecule of small dimensions, through NalophanTM bags has been studied. The diffusion coefficient of H2S through the Nalophan™ film was evaluated using the Fick's law, and it turned out to be equal to 7.55E-12 (m2/s) at a temperature of 23°C and a relative humidity of 60%. This D coefficient entails a reduction of 17% of H2S into 30 hours of storage time. Moreover, the role of humidity on diffusion speed was evaluated by storing the Nalophan™ bags at relative humidity condition of 20% and temperature of 23°C. In this condition, the loss percentage of H2S (%) after 30 h turns out to be equal to about 23%. The results show that the diffusion phenomena are affected by the relative humidity storage condition: by decreasing the relative humidity of storage condition it is observed a weak increase of H2S (%) loss. Also the sampling at high temperature (i.e 75°C or 130°C) was evaluated by heating the filled Nalophan™ bags for 5 minute respectively at 75°C and 130°C and then by storing the Nalophan™ bags at relative humidity condition of 20% or 60% and temperature of 23°C. The results show a loss percentage of H2S after the heat treatment (i.e 75°C or 130°C) of the film not negligible in a range of 30-36%. This behaviour could be attributed to the proximity of the glass transition temperature of the Nalophan™.