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

Exfoliated poly(ethylene terephthalate) (PET) nanocomposite excluding organic modifier (M-PetLSNeom) was successfully prepared by the melt processing via solution method with solvent-nonsolvent system. PET nanocomposites including organic modifier (M-PetLSNiom and D-PetLSN) as counterpart of M-PetLSNeom 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-PetLSNeom was confirmed to be well removed by solution method with solvent-nonsolvent system. Then, it was found that M-PetLSNeom and M-PetLSNiom 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-PetLSN. 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-PetLSNeom, M-PetLSNiom, D-PetLSN, 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-PetLSNiom and D-PetLSN including organic modifier showed lower crystallization constant rates, longer crystallization half times, and poorer optical, thermal, and mechanical properties than M-PetLSNeom. These results were ascribed to the thermal decomposition of the organic modifiers presented in M-PetLSNiom and D-PetLSN during the melt processing.