Abstract
Vapour diffusion in a porous web material followed by its absorption or condensation is a typical process for all porous materials particularly on polymeric and natural basis. The description of kinetic weight increment increase during this process was proposed by use of a relatively simple function with adequately defined theoretical background. It was shown that this kinetic process is controlled by vapour diffusion through porous web material. This tool in connection with observations at different air relative humidity and with use of relatively simple technique enables one to evaluate the structure properties and its structure homogeneity, that is, the uniformity character of the porous stratified web material. Utilization of this description was demonstrated during moistening kinetics of paper web of different composition from primary and secondary fibres on lignocellulosic and only cellulosic basis with different ash content.
Highlights
Condensation of liquid vapour in porous medium is an important phenomenon of behaviour of porous materials
We have distinguished the liquid water in porous systems as (i) self-organized water, that is, bulk of water whose behaviour is independent on the character and composition of porous system, and (ii) medium-enforced organized water, that is, water the organization of which in the porous system, in microreticular system, is controlled by surface-molecular properties of components forming this system
It was shown that the kinetics of important practical absorption vapour processes like vapour condensation and moistening of porous web material can be described using a relative simple function given by (1) with adequately defined theoretical background
Summary
Condensation of liquid vapour in porous medium is an important phenomenon of behaviour of porous materials. We have distinguished the liquid water in porous systems as (i) self-organized water, that is, bulk of water whose behaviour is independent on the character and composition of porous system, and (ii) medium-enforced organized water, that is, water the organization of which in the porous system, in microreticular system, is controlled by surface-molecular properties of components forming this system. The hygroscopicity characterizes behaviour of porous materials and belongs to their very important properties. The hygroscopicity causes advantage of porous products; on the other hand, it causes some discrepancies of their quality These discrepancies hold down application of paper products. The complete understanding of moistening process is a necessary presumption for further paper expanse utilization, for using of paper as packaging material [2, 3]
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