Studies of the heat of vaporization of water associated with cellulose fibers characterized by thermal analysis |
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Authors: | Sunkyu Park Richard A. Venditti Hasan Jameel Joel J. Pawlak |
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Affiliation: | (1) Department of Wood and Paper Science, North Carolina State University, Raleigh, NC 27695-8005, USA |
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Abstract: | The heat of vaporization (H vap) of water associated with cellulose fibers versus moisture ratio was determined using modulated differential scanning calorimetry. A steep increase in the H vap for decreasing moisture ratio was observed at low moisture ratios (0.0–0.3 g/g), indicating a higher energy required to evaporate water interacting with the cellulose. The water molecules with elevated H vap correspond to non-freezing bound water. This may be attributed to (a) energy to break mono and/or multilayer sorption and (b) energy to overcome capillary forces. For polypropylene and glass fibers, H vap was constant versus moisture ratio, in agreement with no non-freezing bound water existing in these systems. It is suggested that non-freezing bound water could be used as an indicator of H vap, and vice versa, at low moisture ratios. |
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Keywords: | Cellulose fibers DSC Heat of vaporization Non-freezing bound water Thermal analysis |
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