The effect of particle size distribution on the dispersion of nanoclays in poly(ethylene terephthalate)/clay nanocomposites

The effects of clay particle size distributions on their dispersion in poly(ethylene terephthalate) (PET)/clay nanocomposites have been studied. A two-step centrifugation method was used to remove large particles from commercial montmorillonite (MMT). Scanning electron microscopy of aqueous dispersions of MMT and centrifuged clay (CMMT) illustrated that average particle size of CMMT in water is much lower than that of MMT in water. PET/clay nanocomposites with MMT and CMMT were prepared by using a modified melt-blending method of mixing PET and a clay-water slurry instead of direct introduction of dried clay. Transmission electron microscopy and X-ray diffraction results showed that CMMT with their smaller particles have better dispersion into the polymer matrix than uncentrifuged MMT. Melt viscosity results revealed that good dispersion of CMMT into the PET matrix reduces the effect of hydrolytic degradation of PET in the presence of water. Differential scanning calorimetry results indicated that the particle size distribution of nanoclays and consequently, the morphology of nanocomposites have a key role on the nucleating effect of clay particles and crystallinity of final samples. Nanoclays with smaller particle size distributions exhibit better dispersion of particles in the polymer matrix and this decreases their nucleating effects and the crystallinity of nanocomposites.