Standardized Testing
Gravimetric measurement protocols for determining the water vapor transmission rate of sheet materials operate under controlled environmental conditions. The standard of tappi t448 evaluates the barrier performance of papers and paperboards at high temperatures and high humidity. This method provides a reliable way to compare different coating treatments and barrier films used in packaging.
Gravimetric Procedure
Specimen testing involves sealing the paperboard sample over the open mouth of a dish filled with a dry desiccant. During the run of tappi t448, the dish assembly is placed in a chamber maintained at twenty-three degrees Celsius and fifty percent relative humidity. Periodic weighings of the assembly track the moisture gain as vapor passes through the board into the desiccant.
This continuous mass measurement provides the transmission rate in grams per square meter per day.
Industrial Application
Food packaging manufacturers utilize this test to predict the storage life of dry food products under moderate conditions. Since polymer coatings must block moisture to prevent food spoilage, this method allows mills to verify the barrier quality of their boards before shipment. This standard provides an essential baseline for checking consistency between different production batches.
It serves to verify that the board meets the humidity requirements of the contract.
