Water-vapour sorption equilibria of a bleached-kraft paperboard - A study of the hysteresis region

Abstract

The moisture sorption equilibria of a bleached-kraft paperboard (mean basis weight 240 g/m2) was investigated experimentally with special attention focused on the hysteresis loop and its interior. The theory of independent domains developed by Everett [11] was utilized to calculate a domain or moisture distribution function from experimental boundary absorption, de sorption and secondary desorption isotherms. The moisture distribution function was used to construct additional EMC paths inside the main hysteresis loop like secondary adsorption curves and spiral trajectories which showed good agreement with experimental data. If recent conjectures regarding correspondence between sorption hysteresis and hysteresis in dimensional changes, stress-strain behaviour and other paper properties are true, it may be possible to explain and correlate hysteresis in these other properties also via Everett's theory of independent domains.