Moisture Hysteresis

Sorption Lag

Variation in the equilibrium moisture content of a fibre based material depends on whether the substrate is approaching equilibrium from a drier or a wetter state. The moisture hysteresis phenomenon means that a sheet of paper will hold more water when drying out than it will when absorbing moisture at the same relative humidity. It represents a fundamental property of the cellulose structure.

Fibre Response

Cellulose fibres contain internal spaces that expand and contract as water molecules enter or leave the cell wall. During the drying process, some of these spaces collapse and form internal bonds that do not immediately reopen when the paper is remoistened. This internal reorganization creates the difference in water retention levels.

Dimensional Change

Practical implications of this effect appear in the printing room when paper is subjected to varying environmental conditions. If a stack of paper reaches a specific humidity via a drying path, it will exhibit different physical dimensions and stiffness than if it reached that same humidity via an absorption path. This can lead to registration issues or curl that cannot be resolved by simple temperature adjustments.

Proper management of the moisture history of the stock prevents unexpected behavior during high speed converting operations.

An open material swatch book displaying varied paper and textile samples rests beside a honeycomb cardboard sheet on a metal workbench.

Secondary Fiber Mechano-Sorptive Coefficient Moisture Hysteresis

Quantification of Mechano-Sorptive Structural Degradation under Multiaxis Transient Vapor Flux in Recycled Fiber Laminates

Recycled fiber laminates experience accelerated creep under transient vapor flux, requiring increased structural safety factors in humid supply chains.

A rendered image shows a multi-axis robotic arm positioned above a specialized flatbed machine, processing a substrate in a controlled industrial setting.

ISO 5628 Sheet Flatness Interlaminar Shear

Quantifying Structural Flexural Modulus Loss in Recycled Paperboard Subjected to Dual-Axis Mechanical Decurling and Fluid Rehydration

Mechanical decurling and fluid rehydration permanently degrade recycled paperboard flexural modulus by shear micro-delamination and fiber plasticization.