钠膨润土在复杂分散体系中的悬浮行为

SUSPENSION BEHAVIOR OF SODIUM-BENTONITE IN COMPLEX DISPERSE SYSTEM

采用相对高度沉降法测量了钠膨润土为悬浮剂的液态模锻涂料的悬浮性。结果表明:随着钠膨润土质量分数的增加,涂料中固体分散相的悬浮性呈上升趋势,但对于不同固体分散相的涂料有一个临界值,超过该值,涂料悬浮性提高不明显甚至出现下降的趋势。仅有钠膨润土做悬浮剂的涂料底部产生沉淀结块,添加羧甲基纤维素钠不仅可以提高钠膨润土的悬浮能力,而且能有效减少沉淀结块的体积。涂料体系中含量较多的高价阳离子(如:Fe3+,Al3+)会严重破坏钠膨润土悬浮作用,使涂料悬浮性变差。水玻璃与钠膨润土配合使用可以提高涂料的悬浮性,而磷酸铝的加入会减弱钠膨润土的悬浮作用。理论分析认为,钠膨润土中的蒙脱石悬浮机理为电吸附网络桥联机理。

Relative height sedimentation method was used to measure the suspensibility of the solid state phase in liquid forging coating with sodium-bentonite as suspending agent. The results show that the suspensibility increases with the increase of sodium-bentonite mass fraction. However, the sodium-bentonite content has a critical value for different aggregate coatings. When it exceeds the critical value, the suspensibility has no obvious increase or even a downward trend. The precipitated caking was found at the bottom of the coating which only has sodium-bentonite as suspending agent. It not only can enhance the levitation capability of sodium-bentonite, but also effectively decrease the amount of the precipitate caking by adding carboxymethyl cellulose sodium. The suspensibility of the coating system will decrease with the decrease of levitation effect of sodium-bentonite due to high content of positive charged ions （such as Fe3＋, Al3＋） in the coating. The suspensibility of the coating with sodium-bentonite as suspending agent can be enhanced by adding sodium silicate, but it can reduce the levitation capability of sodium-bentonite by adding aluminum phos-phate. It is believed that the suspension mechanism of sodium-bentonite is electric network absorption mechanism based on the theo-retical analysis.