Isothermal crystallization kinetics and thermal behavior of poly(?-caprolactone)/multi-walled carbon nanotube composites

This study describes the preparation of poly(?-caprolactone) (PCL)/multi-walled carbon nanotube (MWCNT) composites by ultrasonically mixing the PCL and as-fabricated MWCNT in a tetrahydrofuran solution. The TEM images show that the MWCNT is well separated and uniformly distributed in the PCL matrix. Differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), X-ray diffraction (XRD) and polarized optical microscopy (POM) were used to investigate the isothermal crystallization kinetics, crystalline structure and thermal behavior of PCL and PCL/MWCNT nanocomposites. DSC isothermal results revealed that the activation energy of PCL extensively decreases with increasing MWCNT contents, suggesting that the loading of MWCNT into PCL matrix probably induced heterogeneous nucleation during crystallization processes. From TGA data, the addition of small amount of MWCNT into PCL matrix can improve the thermal stability of PCL matrix. TGA isothermal degradation data illustrate that the activation energy E_d of the composites is smaller than that of PCL. This phenomenon can be attributed to the incorporation of more MWCNT loading into PCL caused a decrease in the degradation rate and an increase in the residual weight for PCL/MWCNT nanocomposites.