TAPPI T402 - Standard conditioning and testing atmospheres for paper, cardboard, and pulp sheets.
TAPPI T402 is a standard practice that defines specific conditions and methodologies for preconditioning, conditioning, and testing of paper, cardboard, pulp sheets, and related products. This standard is crucial for obtaining consistent and reliable results when testing the physical properties of these materials. However, it does not cover special testing atmospheres simulating tropical or arctic environments.
The moisture hysteresis effect is a phenomenon that affects the physical properties of paper and cardboard. This effect depends on whether the sample has been exposed to a particular relative humidity from a higher or lower level. TAPPI T402 provides guidelines for mitigating this effect, enabling more accurate and consistent measurements.
Temperature and relative humidity significantly affect the physical properties of paper, cardboard, and other related materials. For certain properties, a temperature variation of 1°C can have almost as much impact as a 2% variation in relative humidity.
The standard proposes three specific atmospheres:
1. Preconditioning atmosphere, specified as 10 to 35% RH and 22 to 40 °C.
2. Conditioning atmosphere, defined as 50.0% ± 2.0% RH and 23.0 ± 1.0 °C.
3. Testing atmosphere, identical to the conditioning atmosphere.
To maintain the specified relative humidity limits, precise temperature control is required, and any abrupt changes can have a significant impact on relative humidity.
The standard procedure requires specific equipment such as a preconditioning chamber, a conditioning and testing chamber, a hygrometer, and a thermometer. All these tools have defined levels of accuracy and tolerance to ensure precise and consistent results. The setup and operation of these equipment require meticulous attention.