十八烷基三甲基铵改性蒙脱石的结构和凝胶性能关系研究

RELATION BETWEEN STRUCTURE AND COLLOID PERFORMANCE OF OCTADECYL TRIMETHYL AMMONIUM MONTMORILLONITES

利用小角X射线衍射技术研究在不同的十八烷基三甲基铵盐用量下制备的有机蒙脱石的结构特征,将具有不同晶体结构特征的有机蒙脱石分别分散在二甲苯、乙醇混合相和0#柴油中,测定在相应溶剂体系中的凝胶性能,研究发现当十八烷基三甲基铵盐的用量小于0.9 CEC时,十八烷基三甲基铵盐阳离子在蒙脱石层间呈单层平卧排列,由于在有机溶剂中蒙脱石得不到充分的剥离而导致有机蒙脱石的凝胶性能较差,表现为有机凝胶的粘度和胶体率都较低;当十八烷基三甲基铵盐的用量在0.9 CEC^1.8 CEC时,十八烷基铵阳离子在蒙脱石层间呈单层倾斜排列,在有机相中蒙脱石不仅能得到充分的剥离,而且能形成稳定的"卡房式结构",使有机凝胶的黏度和胶体率分别最高达到23 000mPa.s和100%;而当十八烷基铵盐的用量大于1.8 CEC时,十八烷基铵有机物在蒙脱石层间呈胶束排列,尽管在有机相中能得到充分的剥离,但由于过量的有机阳离子中和了蒙脱石层面的负电荷,在体系中不能形成稳定的"卡房式结构",使有机蒙脱石的凝胶粘度较低,而胶体率较高。

Structures of Octadecyl trimethyl ammonium montmorillonites prepared with different dosages of organic modifier were investigated by using small angle XRD. Organic montmorillonites with different structure were dispersed in organic liquids of dimethylbenzene, ethanol mixture and 0^# diesel oil respectively, the gel performance of each organic montmorillonite was measured. This paper studies the relation between the structure and gel performance of organic montmorillonite. When the dosage of Octadecyl trimethyl ammonium is under 0.9 CEC,the octadecyl trimethyl ammonium cations take on lateral monolayer type in interlayer of montmorillonite. The organic montmorillonite cannot be fully peeled off in organic liquids,leading to bad organic gel performance with lower viscosity and gel swelling volume of organic montmorillonite. When the dosage of Octadecyl trimethyl ammonium is between 0.9 CEC～1.8 CEC, the octadecyl trimethyl ammonium cations take on paraffin type in interlayer of montmorillonite. The montmorillonite can not only be fully peeled off,but also form so-called ＂card house＂ in organic liquids. So this kind of organic montmorillontes have the best gel performance,with the gel viscosity and swelling volume of 23 000 mPa·s and 100% respectively. When the dosage of Octadecyl trimethyl ammonium increases to more than 1.8 CEC,the Octadecyl trimethyl ammonium take on colloid bundle type in interlayer of montmorillonite. In such case,although the montmorillonite can be fully pelled off,the excessive octadecyl trimethyl ammonium cation neutralizes the negative charge of montmorillonite layer,preventing the formation of ＂card house＂. This kind of organic montmorillonites have lower gel viscosity and higher swelling volume.