Biodegradable poly(ethylene succinate) nanocomposites. Effect of filler type on thermal behaviour and crystallization kinetics

Nanocomposites based on poly(ethylene succinate) (PES) containing different types of inorganic nanofillers, including graphene oxide, modified graphene oxide, multi-walled carbon nanotubes and silver nanoparticles at a concentration of 2.5 wt% were prepared by solution casting. Good dispersion of the nanomaterial in the polymer matrix was verified with SEM microphotographs. WAXD patterns showed no change in crystal type of PESu in the nanocomposites. Crystallization was studied with DSC and involved non-isothermal melt and cold crystallization, as well as isothermal crystallization from the melt. All nanocomposites presented faster crystallization compared to pristine polymer with MWCNT resulting in the faster crystallization rate. Avrami's method was applied to simulate crystallization kinetic data and a good fitting was observed for the whole relative degree of crystallinity range in pristine PESu and all nanocomposites, except those with MWCNT, where it failed at high conversions. The activation energy of non-isothermal crystallization was calculated using the isoconversional model of Friedman and the nanocomposites with MWCNT exhibited higher values compared to other materials, though corresponding to higher (melt crystallization) or lower (cold crystallization) temperatures. Moreover, MWCNT was found also to have the higher nucleation activity. The Lauritzen-Hoffman analysis was also applied to analyse isothermal crystallization data and the generated morphology on isothermal crystallization from the melt was studied by Polarized Light Microscopy. The size of spherulites decreased as the polymer crystallization was nucleated by the nanoparticles and also the texture was affected.