Effect of Carbon Nanotubes on Thermal Behavior of Poly(L-lactide) and Poly(D-lactide) Electrospun Fibers

Thermal properties and crystallization behavior of electrospun polymer composites fibers of poly (L-lactide) (PLLA) and poly (D-lactide) (PDLA) blended with a small amount of carbon nanotubes (0.1-4 wt{\%}) were systemically studied by differential scanning calorimetry, wide- and small- angle X-ray scattering , and time-resolved Fourier transform infrared spectroscopy. The disordered $\alpha '$-form crystal and the more stable $\alpha $-form crystal in polymer composites are produced respectively at low and high crystallization temperatures (Tc). It was found that the $\alpha '$- to $\alpha $-crystalline phase transition occurs prior to the dominant melting in both polymer composites PLLA and PDLA crystallized at low Tc. We compare the effect of carbon nanotubes on this transition for neat and filled samples. Moreover on increasing the content of CNTs from 0.1 to 4 wt{\%}, the induction period for crystallzation was shortened and the polymer composites' crystallization rate was enhanced. The $\alpha '$- to $\alpha $-crystalline phase transition of PLLA and PDLA was better accelarated at low Tc from 80${^\circ}$ to 120${^\circ}$. With increasing Tc, CNTs have smaller influence on the transition.