Title:
Elucidating the nature of bonding in
mechanical pulps
Elucidating the nature of bonding in
mechanical pulps
Author(s)
Lehtonen, Lauri Kalevi
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Abstract
Bond strength is classically
characterized into two separate factors; area of the bond and specific bond strength.
This separation is especially important in pulps that lack strength properties, and are
specifically used for their optical properties, such as mechanical pulps. In this
research the applicability of the Ingmansson and Thode method for distinguishing
between specific bonded area and specific bond strength in mechanical pulps is
studied. It is shown that the rigid, non-collapsable, nature of the mechanical pulp can
be overcome by press drying the sheets until they approach their 50% relative
humidity moisture content. Mechanical pulps have been assumed to operate in a
domain where fiber failure can be considered insignificant, and the bonded area to
tensile strength relationship is linear. In this study it was shown that most
commercial pulps operate in a significant fiber failure domain. However, it is shown
that pure fines and fines rich mechanical pulp better follow a linear bonded area to
tensile strength relationship rather than a non-linear (significant fiber failure) model,
suggesting that only the fiber fraction undergoes fiber failure and the finer fractions
predominantly bond failure. The Ingmansson and Thode method relies on the use of
scattering coefficient as a measure of specific surface area. It is shown that scattering coefficient is an accurate estimate of mechanical pulp specific surface area
at a constant wavelength of light, provided that the wavelength used to measure scattering coefficient is above the significant absorption limit.
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Date Issued
2004-11
Extent
25828050 bytes
Resource Type
Text
Resource Subtype
Dissertation