2.5.4. Permeability Tests

The water vapor permeability (WVP) of the film samples was determined using the gravimetric method ASTM E96-95 in triplicate. For this, 5 mL of distilled water was placed inside a Payne permeability cup (diameter of 3.5 cm) from Elcometer Sprl (Hermallesous-Argenteau, Belgium). The films were not in direct contact with water but exposed to 100% RH on one side and secured with silicon rings. The samples were placed within a desiccator, filled with dried silica gel, at 0% RH and 25 ◦C. The control samples were cups with aluminum films to estimate the solvent loss through the sealing and samples placed in cups but without permeant to compensate for mass losses due to eugenol release. The cups were weighted periodically using an analytical balance ( ±0.0001 g). WVP was calculated from the regression analysis of weight loss data vs. time and the weight loss was compensated by the marginal losses through the sealing and eugenol release. The permeability was obtained by multiplying the permeance by the film thickness.

Similar as described above for WVP, limonene permeability (LP) was measured placing 5 mL of D-limonene inside the Payne permeability cups. The cups containing the films were placed at the controlled room conditions of 25 ◦C and 40% RH. The samples were measured in triplicate and the limonene vapor permeation rate (LPRT) values were estimated from the steady-state permeation slopes and the weight loss was compensated by the comparatively marginal loss through the sealing and by the fluctuations in mass of the films due to eugenol evaporation and potential water sorption. LP was calculated taking into account the average film thickness in each case.
