Controlled Silylation of Montmorillonite and its Polyethylene Nanocomposites
An alkylammonium modified montmorillonite, Cloisite 20A, was reacted with trimethylchlorosilane in order to replace the edge hydroxyl groups of the clay. Since the reaction will liberate HCl, reactions were performed both in the presence and absence of sodium hydrogencarbonate. Without sodium hydrogencarbonate, the proton, which was generated in situ, could replace a portion of the alkylammonium ions and further react with trimethylchlorosilane. The product, TMS-20H, has a smaller basal spacing than Cloisite 20A itself. If the proton was trapped by the hydrogencarbonate ions, only the edge silanol groups react with trimethylchlorosilane. The product, TMS-20A, maintained the same basal spacing as the precursor. The presence of the edge trimethylsilyl groups were confirmed by thermogravimetric analysis and infrared spectroscopy. Intercalated polyethylene nanocomposite could be fabricated by melt blending polyethylene with TMS-20A, while only microcomposites could be formed using TMS-20H. The structure of the hybrid was characterized by X-ray diffraction and transmission electron microscopy.