In a 100 mL beaker, 50 g anhydrous calcium chloride (particle size of 2 mm) was added. Uniform smooth films without holes or wrinkles were selected. Subsequently, they were measured to determine their thicknesses, sealed at the mouth with molten paraffin, placed in a dryer with 100% relative humidity, measured at 25 °C, and removed from the dryer, and weighed every 24 h. Three parallel experiments were continuously performed for one week, and the results were presented as the arithmetic mean of each group.
where WVP is the water permeability coefficient (g·mm/m2·d·KPa), Δm is the steady mass increment (g), d is the film thickness (mm), A is the effective measured area (m2), T is the time interval (days) of the measurement, and ΔP is the vapor pressure difference (KPa) on both sides of the sample.
The film sealing was measured by placing approximately 5 mL salad oil in a test tube and then sealing it with the film. The oil was further placed upside down on a filter paper for a week to calculate the average oil permeability coefficients of the three samples.
where Poil is the oil permeability coefficient (g·m/m2·d), Δm is the change in the filter paper quality (g), d is the film thickness (mm), A is the film area (m2), and T is the placement time (days).
where WVP is the water permeability coefficient (g·mm/m2·d·KPa), Δm is the steady mass increment (g), d is the film thickness (mm), A is the effective measured area (m2), T is the time interval (days) of the measurement, and ΔP is the vapor pressure difference (KPa) on both sides of the sample.
The film sealing was measured by placing approximately 5 mL salad oil in a test tube and then sealing it with the film. The oil was further placed upside down on a filter paper for a week to calculate the average oil permeability coefficients of the three samples.
where Poil is the oil permeability coefficient (g·m/m2·d), Δm is the change in the filter paper quality (g), d is the film thickness (mm), A is the film area (m2), and T is the placement time (days).
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