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

在-50 ~ 20 C的温度范围内，采用DSC法研究了不同含水量的湿浆板中水分的熔融现象，建立了湿浆评价方法。结束语如下：与纯水熔融DSC曲线相比，湿浆板DSC曲线向低温侧明显展宽。因此，在较低温度侧DSC熔化曲线的形状可以表征具有相当熔合热的纸浆。随着湿纸浆含水率的降低，低亲水性纸浆在DSC熔融曲线低温侧的熔融热增大，而高亲水性纸浆的熔融热减小。两条直线很好地表示了水的含量和熔合热之间的关系。高含水量时的曲线斜率为334 J/g。低含水率时，直线斜率小于高含水率时的直线斜率。虽然不冻水随加热程度的增加而增加，但不冻水的增加太少，不能用于纸浆评价。另一方面，电导率的测量必须更加实用，以评估纸浆的造纸。水含量与熔合热之间存在两条直线关系，DSC曲线向低温侧展宽，表明湿纸浆片中的水存在三种状态，即不冻结、可冻结大块水和可冻结但不同于大块水。

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.