Crystallization behaviour of PEO with carbon-based nanonucleants for thermal energy storage

Carbon-based nanoadditives-carbon black, graphite, carbon fibres, single walls carbon nanotubes (SWCNTs) and fullerenes have been processed with poly(ethylene oxide) (PEO) using a melt-solidification method and characterized for thermal energy storage applications. Results of differential scanning calorimetry investigations for PEO and PEO/nanonucleant systems show that the temperature and heat of phase transition depend on the composition of the blends and kind of carbon additives. For the PEO/fullerene and PEO/SWCNTs blends, higher heats of melting in comparison to theoretical values have been observed, with the highest heat of melting for PEO/fullerenes (90/10, w/w) and PEO/SWCNTs (90/10, w/w). From isothermal kinetic analysis the Avrami exponent for PEO/SWCNTs was calculated as 1.81-2.19, while for PEO/fullerenes (90/10, w/w) its value was in the range of 1.41-2.02. Based on the Hoffman and Weeks theory it has been found that for crystallization of all samples under temperature conditions corresponding to the crystallization regime III, incorporation of SWCNTs and fullerenes lowers the activation energy of nucleation. A shift of absorption bands of C-O stretching vibrations in PEO/SWCNT and PEO/fullerene blends has been found as compared to PEO-the C60 and SWCNT molecules interact with PEO oxygen ethers and reduce the mobility of the polymer chains.