Novel preparation method for improving the dispersion of ionic liquid-modified montmorillonite in poly(ethylene terephthalate)

Thermally stable ionic liquids (ILs) were used to modify clay nanoparticles for use in the preparation of poly(ethylene terephthalate)/clay nanocomposites. Nanoclays with smaller particle size distributions were prepared with a two‐step centrifugation method that removed large particles from commercial montmorillonite (MMT). Scanning electron microscopy of aqueous dispersions of MMT and centrifuged clay (CMMT) illustrated that the average particle size of CMMT in water was much lower than that of MMT in water. Both CMMT and MMT were modified with imidazolium‐ and phosphonium‐based ILs. Fourier transform infrared spectroscopy revealed that the surfactants were associated with the clay surface. Thermal gravimetric analysis results indicated that clays modified with thermally stable ILs degraded above 300°C and could survive PET processing temperatures. Transmission electron microscopy for nanocomposites revealed an improvement in the dispersion of centrifuged nanoclays (modified with both imidazolium and phosphonium ILs) into the polymer matrix compared to non‐centrifuged modified MMT with larger particle sizes. X‐ray diffraction and differential scanning calorimetry data indicated that particle size distributions have a significant effect on the dispersion and rate of crystallization of nanoclays modified with imidazolium surfactants. There was, however, a less important effect of centrifugation on the dispersion of nanoclays modified with phosphonium surfactants. POLYM. COMPOS. 37:1259–1266, 2016. © 2014 Society of Plastics Engineers