Synthesis of quaternary phosphonium salts with ester functional group and its application to improve the thermal stability of modified montmorillonite

Abstract

Both of quaternary ammonium and quaternary phosphonium salts of bis-hydroxyethyl terephthalate (BHET) were successfully synthesized and characterized by fourier transform infrared spectroscopy (FT-IR). These two kinds of salts were used to intercalate Na-MMT to yield two kinds of respective organo-modified MMTs. Basal spacing and thermal stability were investigated by using X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. The experimental results show that, as compared with Na-MMT, basal spacings of both of MMTs modified by the quaternary phosphonium salt of BHET (BHETPP) and the quaternary ammonium salt of BHET (BHEA), increase from 12.4 A to 19.7 A and 31.3 A, respec-tively. Thermal stability of BHETPP-modified MMT is much better than that of BHEA-modified MMT, i e, Tonset of BHETPP-modified MMT is around 400 °C while Tonset of BHEA-modified MMT is near 250 °C. Therefore, with en-larged basal spacing and excellent thermal stability, BHETPP-modified MMT is a promising organo-modified MMT which may be used to prepare polyethylene terephthalate/MMT nanocomposite with high thermal and mechanical performance.