Abstract:

Two polymethyl methacrylate ammonium salts（MAPS-B and MAPS-O）were used to modify montmorillonite. Such thermally stable oligomerically modified montmorillonites were further melt-compounded with polybutylene terephthalate（PBT）at a high temperature and six kinds of nanocomposites（PBT/MAPS-B-1，PBT/MAPS-B-2，PBT/MAPS-B-3，PBT/MAPS-O-1，PBT/MAPS- O-2 and PBT/MAPS-O-3）were obtained. The influence of the structure and content of oligomerically modified montmorillonite on the morphology and properties of the nanocomposites were evaluated. The results of X-ray diffraction（XRD）and transmission electrical microscopy（TEM）indicated that the PBT/MMT nanocomposites had intercalated structures. Increased clay loading was a disadvantage for clay dispersion in the polymer matrix. Thermogravimetric analysis（TGA）showed that thermal stabilities of the PBT/MAPS-B and PBT/MAPS-O nanocomposites were improved remarkably. The onset temperature of thermal degradation（T_onset）of PBT/MAPS-O-2 was 20 ℃ higher than that of the pristine material. The thermal stability of the composites was influenced by the dispersity of clay. The poor dispersity with clay loading higher than 2% resulted in decreased T_onset of PBT/MMT. The effects of modified clays on the crystallization behavior of PBT were characterized by differential scanning calorimeter（DSC）. The results showed that the nanocomposites of polyester/MMT had higher crystallization rate and a little lower melting temperature than the pristine polyester. The crystallization rate increased with increasing MMT content.