Preparation And Properties Of Two Biodegradable Polymers/Multi-Walled Carbon Nanotubes Nanocomposites

In this work, biodegradable poly(3-hydroxybutyrate) (PHB)/functionalized multi-walled carbon nanotubes (f-MWNTs) nanocom-posite was prepared by solution casting method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicate a homogeneous distribution of f-MWNTs in the PHB matrix. Nonisothermal melt crystallization, overall isothermal meltcrystallization kinetics, and crystalline morphology of neat PHB and the PHB/f-MWNTs nanocomposite were studied by differential scanning calorimetry (DSC), hot stage polarizing microscopy (POM) in detail. It is found that the presence of f-MWNTs enhances the crystallization of PHB during nonisothermal and isothermal melt crystallization processes in the nanocomposite due to the heterogeneous nucleation effect of f-MWNTs. The crystallization rate of PHB is markedly enhanced while the crystallization mechanism remains almost unchanged in the nanocomposites. POM result reveals an obvious smaller spherulite for the nanocomposite while the crystal structure of PHB in the nanocomposite is not changed as evidenced by the WAXD result. Moreover, the incorporation of a small quantity of f-MWNTs apparently improves the thermal stability of the PHB/f-MWNTs nanocomposite with respect to neat PHB. Two methods are employed to study the activation energies of thermal degradation for both the neat PHB and the PHB/f-MWNTs nanocomposite. The activation energy of thermal degradation of the PHB/f-MWNTs nano-composite is higher than that of neat PHB.Biodegradable poly(ε-caprolactone) (PCL) and its nanocomposites at low multi-walled carbon nanotubes (MWNTs) loadings were prepared in this work through simple melting compounding. SEM and TEM observation indicates a homogeneous and fine distribution of MWNTs throughout the PCL matrix. Nonisothermal melt crystallizationbehavior and isothermal melt crystallization kinetics of neat PCL and its nanocomposites were investigated with DSC. In the case of nonisothermal melt crystallization, the crystallization peak temperatures of PCL are higher in the nanocomposites than in neat PCL at various cooling rates. In the case of isothermal melt crystallization, the overall crystallization rate is faster in the nanocomposites than that in neat PCL. However, the crystallization mechanism does not change. The enhanced crystallization of PCL in the nanocomposites arises from the strong nucleation agent effect of MWNTs. In addition, the incorporation of a small quantity of MWNTs has improves apparently the mechanical properties of the PCL/MWNTs nanocomposites with respect to neat PCL.