The Application of Differential Scanning Calorimetry (DSC) to Pulp Evaluation

本文用差示扫描量热法（DSC）在-50 ℃ ~ 20 ℃范围内研究了不同含水率的湿浆板中水的熔化现象，以建立纸浆的评价方法。结论如下。与纯水的熔融DSC曲线相比，湿浆片的DSC曲线明显向低温侧加宽。DSC熔融曲线在低温侧的形状可以表征具有相当熔融热的纸浆.随着湿浆片含水量的降低，亲水性较低的浆片在DSC熔融曲线低温侧的熔化热增加，而亲水性较高的浆片在DSC熔融曲线低温侧的熔化热降低.水含量和熔化热之间的关系用两条直线很好地表示。在较高水含量下的线的斜率给出本体水的熔化热的值为334 J/g。在低含水率下，直线的斜率小于高含水率下的斜率.尽管不冻水随打浆度的增加而增加，但不冻水的增加太小，不能用于纸浆的评价。另一方面，电导率的测量必须更实用才能评价造纸用纸浆。5.水含量与熔化热之间存在两条直线关系，DSC曲线向低温侧变宽，表明湿浆片中水的三种状态，即，不冻的、可冻的散装水和可冻但不同于散装水。

The melting phenomena of water in the wet pulp sheets at different water contents have been investigated by DSC within the temperature range from -50ﾟC to 20ﾟC for the various pulps in order to develop the pulp evaluation method. The concluding remarks are as follows.1. Comparing with the melting DSC curve of pure water, the DSC curve of wet pulp sheet clearly broadened toward the lower temperature side. The shape of DSC melting curve at lower temperature side may therefore characterize pulps provided a comparable heat of fusion.2. With decreasing water contents of the wet pulp sheet, the heat of fusion at lower temperature side of DSC melting curve increased for the less hydrophilic pulp, but decreased for the more hydrophilic pulp.3. The relationship between water contents and the heat of fusion is well represented by two straight lines. The slope of the line at the higher water contents gave a value of 334 J/g for the heat of fusion of bulk water. At the lower water contents, the slope of the straight line is smaller than that at the higher water contents.4. Although nonfreezing water increased with increasing the beating degree, the increase of nonfreezing water is too small to employ for pulp evaluation. On the other hand, the electrical conductivity measurement must be more practical to evaluate the pulp for papermaking.5. The existence of two straight lines in the relationship between water contents and the heat of fusion and the broadened DSC curve toward lower temperature side indicated three states of water in the wet pulp sheets, i.e., nonfreezing, freezable bulk, and freezable but different from bulk water.