Effect of MWNTs concentration and cooling rate on the morphological, structural, and electrical properties of non-isothermally crystallized PEN/MWNT nanocomposites

The effect of multiwall carbon nanotubes (MWNT) concentration and cooling rate on the morphological, structural and electrical properties of non-isothermally crystallized Poly(ethylene naphthalate) nanocomposites (PEN/MWNT) was studied. PEN/MWNT nanocomposites containing 1 and 2 wt % of nanotubes were prepared by melt blending in a mini twin screw extruder. Nanocomposite samples with different degree of crystallinity (X-c) were obtained via non-isothermally crystallization at cooling rates of 2, 10, 20, and 300 degrees C min(-1). In this study it was demonstrated that carbon nanotubes and cooling rate strongly influence morphological and structural characteristics of PEN. Calorimetric results showed that the peak crystallization temperature (T-c) of PEN nanocomposites was increased approximate to 9 degrees through heterogeneous nucleation with respect to pure PEN. X-ray diffraction revealed that carbon nanotubes modify the crystalline structure of PEN favoring the formation of -crystals, and this effect increases with the nanotubes content. On the basis of X-ray scattering analysis, the variation of lamellar thickness revealed that nanotubes promote the formation of lamellar crystals with average thickness of 20 nm at different cooling rates. These structural and morphological changes play an important role on the electrical properties of nanocomposites. It was found that higher concentration of nanotubes and crystallinity promotes electrical conductivity of nanocomposites in the order of semiconductors (until 1 x 10(-4) S cm(-1)) as well as permittivity of 20 at different tested frequencies. This may due to the interconnected networks of nanotubes throughout the crystalline structure formed in PEN nanocomposites. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41765.