(267d) Transport Properties Of Paper Structures From X Ray Microtomography

The permeability of paper is an important property determining the response of sheets to thermal pulses in photocopying and digital printing. Moisture diffusivity is critical in determining paper's strength and mechanical properties. The relationship between permeability, diffusivity and thermal conductivity of paper and its structure is currently lacking.

This paper describes some of our recent work in determining these transport properties for paper structures reconstructed by X Ray Microtomographic techniques. High resolution reconstructions of the fiber and pore spaces within paper samples (at sub-micron voxel sizes) were obtained from radiographs of high intensity synchrotron radiation. The reconstructed pore space was used to conduct transport simulations for permeability, conductivity and diffusivity. These were then compared with experimental data of these properties on the same paper sheets.

A correlation length for the permeability is obtained and is used for determining the effect of heterogeneities on transport properties of paper structures.

A method of Brownian motion simulation accounting for water movement within the fiber space as well as the pore space was developed. This allows us to calculate the diffusivity parameters for paper sheets for both condensed water and water vapor diffusing through the pore space.

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