Thermally stable exfoliated poly(ethylene terephthalate) (PET) nanocomposites as prepared by selective removal of organic modifiers of layered silicate

Abstract

Exfoliated poly(ethylene terephthalate) (PET) nanocomposite excluding organic modifier (M-P etLSN eom) was successfully prepared by the melt processing via solution method with solvent–nonsolvent system. PET nanocomposites including organic modifier (M-P etLSN iom and D-P etLSN) as counterpart of M-P etLSN eom were prepared by using the melt processing via solution method without solvent–nonsolvent system and the only conventional direct melt mixing process, respectively. From elemental analysis (EA) and thermogravimetric analysis (TGA), organic modifier in M-P etLSN eom was confirmed to be well removed by solution method with solvent–nonsolvent system. Then, it was found that M-P etLSN eom and M-P etLSN iom had exfoliated structure by wide angle X-ray diffraction (WAXD) and high-resolution transmission electron microscopy (HR-TEM), whereas no expansion of gallery height was observed for D-P etLSN. To elucidate the effect of organic modifier on the physical properties of PET nanocomposites, the crystallization behavior, optical transparency, thermal stability, and mechanical properties of M-P etLSN eom, M-P etLSN iom, D-P etLSN, and neat PET were evaluated by differential scanning calorimetry (DSC), UV–visible (UV–vis) spectroscopy, TGA, and universal testing machine (UTM). All of the PET nanocomposites exhibited faster crystallization kinetics and better thermal and mechanical properties compared to neat PET due to the presence of silicate layer in PET. However, M-P etLSN iom and D-P etLSN including organic modifier showed lower crystallization constant rates, longer crystallization half times, and poorer optical, thermal, and mechanical properties than M-P etLSN eom. These results were ascribed to the thermal decomposition of the organic modifiers presented in M-P etLSN iom and D-P etLSN during the melt processing.