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Elucidating the nature of bonding in mechanical pulpsLehtonen, Lauri Kalevi 11 1900 (has links)
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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Effects of Coating Formulations on Thermal Properties of Coating LayersLiang, Chong 15 February 2010 (has links)
The effects of coating formulation on thermal characteristics of coating layers were systematically studied for xerographic toner fusion on coated papers. Model coatings were formulated using three types of ground calcium carbonate and one kaolin pigments, each mixed with 6, 10, 18, and 25 pph of styrene butadiene latex binder. Porosity was found to be a key parameter for coating thermal conductivity adjustment, and was determined by the latex concentration. The particle size distribution and morphology of pigments also affect the overall thermal characteristics of coating layers. Print qualities on model coated papers were evaluated by print gloss measurement, toner adhesion test, and pair-wise visual ranking, and it was proved that print gloss is reduced with increasing bulk thermal conductivity of coating layers. The coating layer consisted of Covercarb HP pigment and 10 pph of latex was found to have the best performance in the three print quality evaluation tests.
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Effects of Coating Formulations on Thermal Properties of Coating LayersLiang, Chong 15 February 2010 (has links)
The effects of coating formulation on thermal characteristics of coating layers were systematically studied for xerographic toner fusion on coated papers. Model coatings were formulated using three types of ground calcium carbonate and one kaolin pigments, each mixed with 6, 10, 18, and 25 pph of styrene butadiene latex binder. Porosity was found to be a key parameter for coating thermal conductivity adjustment, and was determined by the latex concentration. The particle size distribution and morphology of pigments also affect the overall thermal characteristics of coating layers. Print qualities on model coated papers were evaluated by print gloss measurement, toner adhesion test, and pair-wise visual ranking, and it was proved that print gloss is reduced with increasing bulk thermal conductivity of coating layers. The coating layer consisted of Covercarb HP pigment and 10 pph of latex was found to have the best performance in the three print quality evaluation tests.
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