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

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, T onset of BHETPP-modified MMT is around 400 °C while T onset 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.