Isothermal Crystallization Behavior of Poly(ε-Caprolactone) Diol/Functionalized-Multiwalled Carbon Nanotube Composites

Isothermal crystallization behavior of poly (epsilon-caprolactone) diol (PCL)/functionalized-multiwalled carbon nanotube (f-MWNTs) composites at three different temperatures (30 degrees, 35 degrees, 40 degrees C), with varying molecular weights (MW) of PCL (2000, 4000, 8000g/mol) and loadings of f-MWNTs (0, 0.1, 1.0, 5.0 wt.%), was studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction methods. DSC isotherm showed that introduction of f-MWNTs into PCL induced a heterogeneous nucleation in the crystallization growth process, thereby lowering the activation energy for the crystallization process appreciably. POM showed the spherulite structure of neat PCL, whereas the composites showed the spherulite structure containing f-MWNTs at the center, indicating nucleating action of f-MWNTs in the crystallization process. The spherulite size decreased but its number increased with increasing weight proportion of f-MWNTs and MW of PCL.