Thermal characterization of surfactant-modified montmorillonites
Thermal characterization of surfactant-modified montmorillonites
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DOI：
10.1346/ccmn.2005.0530308
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发表时间：
2005-06-01
影响因子：
2.2
通讯作者：
Frost, RL
中科院分区：
文献类型：
--
作者：
He, HP;Ding, Z;Frost, RL
表面改性粘土的热稳定性在有机粘土基纳米复合材料的合成和加工中起着关键作用。采用差热分析（DTA）、热重分析（TG）和差示扫描量热分析（DSC）对不同表面活性剂浓度下十六烷基三甲基溴化铵改性蒙脱土的热稳定性进行了表征。差示扫描量热法分析表明，表面活性剂在蒙脱石层间的分子环境与体相不同。改性蒙脱土的DTA曲线在70-100 ℃处出现吸热峰，这是由于表面活性剂的相转变以及自由水和层间水的损失造成的。随着蒙脱土表面堆积密度的增加，改性蒙脱土中的水含量逐渐减少，说明有机粘土的疏水性能得到了改善。随着表面活性剂初始浓度的增加，有机粘土的表面堆积密度逐渐增加，并趋于饱和状态，但随着表面活性剂初始浓度的增加，有机粘土的热稳定性降低。结果表明，阳离子表面活性剂不仅通过阳离子交换作用进入蒙脱石层间，而且通过物理吸附作用进入蒙脱石层间。
The thermal stability of surfactant-modified clays plays a key role in the synthesis and processing of organoclay-based nanocomposites. Differential thermal analysis (DTA), thermogravimetric measurement and differential scanning calorimetry (DSC) were used in this study to characterize the thermal stability of hexadecyltrimethylammonium bromide-modified montmorillonites prepared at different surfactant concentrations. Analysis by DSC shows that the molecular environment of the surfactant within the montmorillonite galleries is different from that in the bulk state. The endothermic peak at 70-100 degrees C in the DTA curves of the modified montmorillonites is attributed to both the surfactant phase transformation and the loss of free and interlayer water. With an increase of surfactant-packing density, the amount of water residing in the modified montmorillonite decreases gradually, reflecting the improvement of the hydrophobic property for the organoclay. However, the increase in the surfactant packing density within the galleries leads to a decrease in the thermal stability of the organoclays.With an increase of initial surfactant concentration for the preparation of organoclays, the surfactant-packing density increases gradually to a 'saturated' state. It was found that the cationic surfactant was introduced into the montmorillonite interlayer not only by cation exchange but also by physical adsorption.