TAPPI/ANSI T 402 Conditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets, and Related Products
TAPPI/ANSI T 402 testing defines the standard atmospheres for normal preconditioning, conditioning, and testing of paper and paper products, paperboard, fiberboard, and containers made from them. The TAPPI/ANSI T 402 test standard also specifies procedures for handling these materials in order that they may reach equilibrium with the respective atmosphere.
TAPPI/ANSI T402 is also applicable to standard pulp test handsheets, except that the preconditioning procedure is omitted, that is, the sheets are not dried to conditions below those obtained by exposure to the standard conditioning and testing atmospheres. This standard practice does not include special conditioning and testing atmospheres, such as those that attempt to simulate tropical or arctic environments.
The physical properties of a sample at 50% RH depend on whether the sample was brought to 50% from higher or lower relative humidity; this “humidity hysteresis effect” is 5-25% of the test value for many physical properties. For example, a hysteresis effect of 1% moisture content (or 16% of the test value of 6% moisture content) is typical. Preconditioning on the dry side within the range specified will avoid most of the hysteresis effect and result in the moisture content of a given sample being established within 0.15% when the sample is later conditioned to 50% RH and 23oC. Conditioning down to 50% gives most papers a moisture content very nearly the same as conditioning up to 60%.
Both temperature and relative humidity have significant effects on the physical properties of paper and board (1, 2). For some properties of paper and board (e.g., MD tensile and CD stretch) a change of 1oC may have nearly as much effect as a change of 2% RH. For synthetic fibers and plastic laminates, the temperature effect may be greater than the RH effect.
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