Biodegradable poly(ethylene succinate) nanocomposites. Effect of filler type on thermal behaviour and crystallization kinetics George Z. Papageorgiou a, b, * , Zoe Terzopoulou a , Dimitris S. Achilias a , Dimitrios N. Bikiaris a , Maria Kapnisti b , Dimitrios Gournis c a Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece b Technological Educational Institute of Thessaloniki, Sindos GR -574 00, Thessaloniki, Greece c Department of Materials Science and Engineering, University of Ioannina, Ioannina GR-45110, Greece article info Article history: Received 18 January 2013 Received in revised form 29 May 2013 Accepted 9 June 2013 Available online 17 June 2013 Keywords: Biodegradable polymers Poly(ethylene succinate) Nanocomposite abstract Nanocomposites based on poly(ethylene succinate) (PES) containing different types of inorganic nano- fillers, 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 corre- sponding to higher (melt crystallization) or lower (cold crystallization) temperatures. Moreover, MWCNT was found also to have the higher nucleation activity. The LauritzeneHoffman 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. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Recently, an increasing interest in biodegradable polymers, such as aliphatic polyesters has appeared. Biodegradable polyesters can be either naturally occurring or chemically synthesized. Poly(- ethylene succinate), PESu, is a biodegradable aliphatic semi- crystalline polyester synthesized by the polycondensation of an aliphatic diacid (i.e. succinic acid) and an aliphatic diol (i.e. 1,2- ethanediol). PESu shows besides biodegradability also very attrac- tive properties including, melt processability, chemical resistance and mechanical properties similar to that of high density poly- ethylene and polypropylene. These properties give to PESu wide potential applications [1e 7]. The formation of hybrid nanocomposite materials based on a polymeric matrix with some inorganic nanofiller results in a syn- ergetic effect of the two respective components in the nanometer scale leading to considerable improvements of various character- istics of the pristine polymer, such as mechanical, thermal, and gas- barrier properties [8]. The small size of the fillers leads to a dra- matic increase in interfacial area and this creates a significant volume fraction of interfacial polymer with properties different from the bulk polymer even at low loadings [9]. Typical filler amounts of less than 5 wt% result in effective enhancement of the nanocomposite properties [10]. There is a large variety of inorganic nanofillers, including nanotubes, layered silicates (e.g., montmo- rillonite, saponite), nanoparticles of metals (e.g., Au, Ag), metal oxides (e.g., TiO 2 , Al 2 O 3 ), semiconductors (e.g., PbS, CdS), and so forth [11]. Carbon nanotubes (CNTs) which were first reported by Iijima [12]. Carbon nanotubes in addition to the exceptional mechanical properties, also posses superior thermal and electric properties: * Corresponding author. Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki GR-541 24, Greece. Tel.: þ30 2310 997812. E-mail address: gzpap@chem.auth.gr (G.Z. Papageorgiou). Contents lists available at SciVerse ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymer.2013.06.005 Polymer 54 (2013) 4604e4616