Carbon nanotube surface-induced crystallization of polyethylene terephthalate (PET)

The crystallization of polyethylene terephthalate (PET) and its effect on the electrical behavior of nanocomposites of PET and carbon nanotubes (CNTs) was studied. A series of nanocomposites composed of polyethylene terephthalate/carbon nanotubes (PET/CNTs) containing 0, 1 and 2% wt/wt carbon nanotubes were prepared by melt extrusion. The morphology developed by the nanocomposites during non-isothermal crystallization at different cooling rates was evaluated using various experimental techniques. Thermal analysis showed an increase in the crystallization temperature of the nanocomposites, which was associated with the nucleation ability of the CNTs, and confined growth that resulted in a 3D-to-1D reduction in the crystallite geometry of the nanocomposites. X-ray diffraction indicated that the crystal structure of the nanocomposites was not affected by the presence of carbon nanotubes or the cooling rate. However, the crystallinity of PET and the nanocomposites increased as the cooling rate decreased. The electrical conductivity of the materials as a function of the cooling rate, at a constant CNT content, showed a marked (two orders of magnitude) increase in passing from the amorphous state to the crystalline state. The results of theoretical calculations indicated self-assembly between the surface of the nanotubes and the aromatic ring of PET; it was proposed that the stacking of aromatic rings on the surface of the nanotubes has an effect on the rearrangement of electric charge.