Water vapor transmission rate testing is normally employed in establishing the degree of protection of a material against the passage of moisture. The ingress of moisture can also have a huge impact on the stability of the products, particularly the moisture-sensitive ones, e.g., pharmaceuticals, food, and electronic parts. WVTR testing gives quantitative information on the permeability properties of films, sheets, laminates, and coated substrates. The findings are beneficial in enabling manufacturers to optimise material formulations and appropriate barrier layers. Testing normally occurs under standardized temperature and humidity conditions to ensure reproducibility. WVTR testing has become a standard ingredient in the product development and material characterization as a result of growing demand in high performance barrier materials.
Principle and Methodology
The WVTR testing principle works on the concept of measuring the amount of water vapor that passes through an area over time. A test specimen is placed between two environments that are of varying humidity. The water vapor moves through the material as it moves out of the area of high humidity to the area of low humidity. The moisture passed is gravimetrically measured or through the humidity sensors that detect the changes in the humidity. The results are determined as the mass of water vapor passed per unit area per day. The temperature, relative humidity, and air flow are controlled to provide accuracy and repeatability of the results.
