The effect of nanomaterials on the solidstate polycondensation (SSP) of PET was investigated using intrinsic viscosity measurement, wide-angle X-ray diffraction, differential scanning calorimetry, and polarizing microscope. The results showed that the montmorillonite nanomaterials could greatly increase the rate of solid-state polycondensation of PET, probably due to the nucleation of montmorillonite nanomaterials for PET crystallization, which resulted in lower crystallinity, more small crystals, and more surfaces of the crystals. The surfaces of microcrystal and richer amorphous regions benefitted the polycondensation reaction of PET and diffusion of volatile by-products, which led to the higher rate of SSP. (C) 2004 Wiley Periodicals, Inc.