Thermal stability, crystallization, structure and morphology of syndiotactic 1,2-polybutadiene/organoclay nanocomposite

Syndiotactic 1,2-polybutadiene/organoclay nanocomposites were prepared and characterized by thermogravimetry analysis (TGA), X-ray diffraction (XRD), polarized optical microscopy (POM), and differential scanning calorimetry (DSC), respectively. The XRD shows that exfoliated nanocomposites are formed dominantly at lower clay concentrations (less than 2%), at higher clay contents intercalated nanocomposites dominate. At the same time, the XRD indicates that the crystal structures of sPB formed in the sPB/organoclay nanocomposites do not vary, only the relative intensity of the peaks corresponding to (0 1 0) and (2 0 0)/(1 1 0) crystal planes, respectively, varies. The DSC and POM indicate that organoclay layers can improve cooling crystallization temperature, crystallization rate and reducing the spherulite sizes of sPB. TGA shows that under argon flow the nanocomposites exhibit slight decrease of thermal stability, while under oxygen flow the resistance of oxidation and thermal stability of sPB/organoclay nanocomposites were significantly improved relative to pristine sPB. The primary and secondary crystallization for pristine sPB and sPB/organoclay (2%) nanocomposites were analyzed and compared based on different approaches. The nanocomposites exhibit smaller Avrami exponent and larger crystallization rate constant, with respect to pristine sPB. Primary crystallization under isothermal conditions displays both athermal nucleation and three-dimensional spherulite growth and under nonisothermal processes the mechanism of primary crystallization becomes very complex. Secondary crystallization shows a lower-dimensional crystal growth geometry for both isothermal and nonisothermal conditions. The activation energy of crystallization of sPB and sPB/organoclay nanocomposites under isothermal and nonisothermal conditions were also calculated based on different approaches. (c) 2007 Elsevier Ltd. All rights reserved.