Drug packaging materials, also known as drug packaging materials, are mainly used to prevent moisture and oxidation, effectively ensuring that drugs are not damaged during transportation and storage.

The water vapor transmission rate refers to the amount of water vapor that passes through a unit area of packaging material for 24 hours under constant humidity difference and temperature conditions. The water vapor transmission rate is an important indicator for measuring the moisture resistance of packaging materials. There are four methods for testing the water vapor transmission rate of pharmaceutical packaging materials, including cup method and weight method. Both the cup method and the weight method are tested by using a moisture permeable cup as a carrier and weighing with a balance under constant temperature and humidity conditions. But there are also differences between them.

Differences in water vapor transmission rate testing between cup method and weight method

1. Different temperature and humidity requirements

Cup test conditions:

A temperature of 23 ℃± 0.5 ℃, relative humidity of 90% ± 2%

B temperature 38 ℃± 0.5 ℃, relative humidity 90% ± 2%

Weight method testing conditions:

A temperature of 40 ℃± 2 ℃, relative humidity of 25% ± 5%

B temperature 25 ℃± 0.5 ℃, relative humidity 40% ± 5%

C temperature 30 ℃± 0.5 ℃, relative humidity 35% ± 5%

2. Different directions of water vapor transmission

The cup method requires a desiccant to be placed inside the breathable cup, and a high humidity environment to be provided outside the cup, allowing water vapor to permeate from the outside to the inside of the breathable cup. Calculate the water vapor transmission rate by testing the weight increase of the moisture permeable cup. The cup method is also known as the weight gain method.

The weight method requires water to be placed inside the breathable cup and a low humidity environment to be provided outside the cup, allowing water vapor to permeate from the inside to the outside of the breathable cup. Calculate the water vapor transmission rate by testing the weight loss of the moisture permeable cup. Cup style method is also known as weight loss method.

3. Different packaging forms for testing

The cup method is generally used to test thin film slices with a water vapor transmission rate of not less than 2g/m2 • 24h. For example, PVC hard sheet, low resistance aluminum foil, three-layer composite film, five layer co extruded film, and so on.

The weight method is generally used to test oral or topical liquid bottles, solid bottles, infusion containers, etc. For example, solid medicine bottles, infusion bottles, infusion bags, etc. packaged in hard sheets.

4. Different requirements for testing equipment

The cup method requires the equipment to provide a high humidity environment, while the weight method requires the equipment to provide a low humidity environment.