Permeation Measurement
Quantitative measurement of moisture vapor mass passing through barrier packaging substrates per unit area and time establishes shelf-life performance limits. Standardized laboratory evaluation via a wvtr test determines the rate of water vapor flux through paperboard laminates, polymer films and coated packaging substrates under controlled relative humidity and temperature gradients. Results express flux in grams per square metre per twenty-four hours under specified climatic conditions.
Maintaining barrier performance prevents crisp products from absorbing ambient moisture and dry foods from clumping inside retail packaging.
Gravimetric Procedure
Testing methods employ dish cup gravimetric techniques or electrolytic sensor detection systems according to standards like ASTM E96 and ISO 15106. Executing a wvtr test using gravimetric dry cup methods seals paperboard samples over a desiccant inside a test cup, measuring weight gain over time as moisture diffuses inward from a humid test chamber. Electrolytic sensors accelerate testing by measuring modulated infrared absorption or electrical current generated as moisture passes through the specimen.
Pinholes and micro-cracks in barrier layers elevate measured vapor flow rates.
Climatic Control
Standard test conditions run at thirty-eight degrees Celsius and ninety percent relative humidity to simulate tropical storage environments. Environmental fluctuations during a wvtr test distort permeation calculations.
