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首页> 外文期刊>Macromolecules >Thermodynamics of amorphous starch-water systems. 1. Volume fluctuations
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Thermodynamics of amorphous starch-water systems. 1. Volume fluctuations

机译：无定形淀粉-水系统的热力学。 1.音量波动

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This paper presents dilatometric and calorimetric experiments on potato starch extruded into a transparent amorphous glass with a density of 1.5 g/cm(3) at room temperature. The specific heat increment at the glass transition is used to estimate the transition temperature of samples containing up to 25 wt % water. The specific volume of the samples is studied between 25 and 165 degrees C and between 0.1 and 100 MPa. Glass transitions estimated from the compressibility increment at the transition temperature are found in agreement with those detected by calorimetry. In the entire experimental temperature range, a maximal excess volume of mixing is observed at a composition corresponding to three water molecules per anhydroglucose in the mixture. This suggests that the large size difference between the chemical components allows the water molecules to saturate only one hydroxyl group of the anhydroglucose at a time. Specific volumes of starch glasses and melts are superimposed onto a single master curve by a simple empirical relation. The neglect of polar interactions in mean field equations of state results in underestimated internal pressures and cohesive energy densities. Free volumes estimated with the lattice fluid equation of state reflect semiquantitatively the effects of temperature and concentration on the density of starch, which goes through a maximum value at low water concentration. Such a reduction of the free volume of polymer glasses by low plasticizer concentrations is called antiplasticization, as the reduction of the glass transition temperature is then coupled to an increase rather than a decrease of elastic moduli. Antiplasticization reduces gas sorption and permeation rates and the knowledge of its occurrence can be used to optimize the gas barrier properties of polymers. [References: 47]
机译：本文介绍了在室温下将马铃薯淀粉挤出到密度为1.5 g / cm（3）的透明无定形玻璃中的膨胀计和量热实验。玻璃化转变温度的比热增量用于估算含水量最高为25 wt％的样品的转变温度。在25至165摄氏度和0.1至100 MPa之间研究了样品的比容。发现由转变温度下的可压缩性增量估计的玻璃化转变与通过量热法检测到的一致。在整个实验温度范围内，在对应于混合物中每个脱水葡萄糖三个水分子的组成下，观察到最大的混合过量。这表明化学成分之间的大尺寸差异允许水分子一次仅使脱水葡萄糖的一个羟基饱和。通过简单的经验关系，将比体积的淀粉玻璃和熔体叠加到一条主曲线上。忽略平均状态方程中的极性相互作用会导致内部压力和内聚能密度被低估。用晶格流体状态方程估算的自由体积半定量地反映了温度和浓度对淀粉密度的影响，该淀粉密度在低水浓度下达到最大值。低增塑剂浓度对聚合物玻璃自由体积的这种减少称为抗增塑，因为玻璃化转变温度的降低随后与弹性模量的增加而不是减少相关。抗塑化作用降低了气体的吸附和渗透速率，其发生的知识可用于优化聚合物的气体阻隔性能。 [参考：47]

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