Effects of polylactide-functionalized multi-walled carbon nanotubes on the crystallization behavior and thermal stability of poly (L-lactic acid)

In this work, poly (L-lactic acid) (PLLA) grafted multi-walled carbon nanotubes (MWCNTs-g-PLLA) was prepared by ring-opening polymerization of L-lactide (L-LA) from hydroxylated MWCNTs (MWCNTs-OH). The grafted product was characterized by Fourier transform infrared spectrometer and X-ray diffraction. It is found that MWCNTs-g-PLLA exhibits a carbonyl (CO) stretching vibration peak in PLLA at near 1758 cm(-1); the crystal diffraction peaks of MWCNTs-g-PLLA at 25.9 degrees, 16.7 degrees, 19.1 degrees, and 21 degrees are same as the peak positions of MWCNTs-OH and PLLA, indicating that the grafted product is synthesized successfully. Then, MWCNTs-OH/PLLA(48k) and MWCNTs-g-PLLA/PLLA(48k) composites were obtained by solution blending with different contents. The effects of MWCNTs-OH and MWCNTs-g-PLLA on the crystallization behavior and thermal stability of PLLA(48k) homopolymer were investigated by differential scanning calorimetry (DSC), polarized light microscopy and thermogravimetric analysis. The results show that the crystallinity and the maximum crystallization rate of the blends increases, and the decomposition temperature of the blends increases by above 50 degrees C.