The effects of gamma irradiation on the morphology and properties of polylactide/Cloisite 30B nanocomposites Lynda Zaidi a , Stéphane Bruzaud b, * , Mustapha Kaci a , Alain Bourmaud b , Nicolas Gautier c , Yves Grohens b a Laboratoire des Matériaux Organiques, Faculté de la Technologie, Université Abderrahmane Mira, Bejaia 06000, Algeria b Laboratoire d’Ingénierie des Matériaux de Bretagne, Equipe E2PIC, Université de Bretagne-Sud, Rue de Saint Maudé, 56321 Lorient Cedex, France c Institut des Matériaux Jean Rouxel, Centre de Microcaractérisation, 2 Rue de la Houssinière, 44322 Nantes Cedex 3, France article info Article history: Received 9 May 2012 Received in revised form 12 September 2012 Accepted 13 September 2012 Available online 6 October 2012 Keywords: Polylactide Clay Nanocomposites Degradation Gamma irradiation abstract The oxidative degradation of neat polylactide (PLA) and PLA-Cloisite 30B (C30B) nanocomposites under gamma irradiation was studied for irradiation doses ranging from 0 to 200 kGy. The morphologies and the properties of neat PLA and PLA-C30B nanocomposites (5 wt.%) were investigated using Fourier transform infrared spectroscopy (FT-IR), size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (ATG), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation measurements. The results were analysed by comparing the C30B influence on the PLA degradation. Results show neat PLA is strongly degraded by gamma irradiation while PLA-C30B nanocomposites are less affected because gamma irradiation promotes the C30B layer distribution within the PLA matrix. The morphological defects were much less more pronounced for the PLA nanocomposites compared to neat PLA, for which many voids and cracks were observed after irradiation. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction During the last decade, much attention has been focused on both biodegradable polymers that can be produced from renewable resources and on polymer layered silicate nanocomposites. The introduction of nanofillers in biodegradable matrices has allowed improving the range of properties and possible uses of these environmental-friendly polymers [1,2]. Among all these biosourced and biodegradable polymers, polylactide (PLA) is one of the biodegradable polymers that can be used as promising alternative to the petroleum-based commodity materials [3,4]. PLA has good mechanical properties, thermal plasticity, high degree of trans- parency and biocompatibility, therefore PLA holds tremendous promise for various end-use applications such as biomedical fields, household, engineering, packaging industries and so on [5e8]. We have previously shown that significant layered nanofiller dispersion into PLA can be successfully accomplished using melt intercalation technique [9]. In this work, it has been concluded that production of a nanocomposite based on PLA associated to Cloisite 30B (C30B) can be an efficient route to extend the application of the polymer as a biodegradable material, with the possibility to finely tune properties by adjustment of the nanofiller content. Moreover, the degradation of PLA-C30B nanocomposites under natural weathering was also investigated as a function of clay loading. All the results show that introducing the organophilic clay into PLA matrix promotes the degradation rates of the nanocomposite samples and this effect is much more pronounced for the samples containing high level of C30B [10]. Many workers have studied the thermal, oxidative or hydrolytic stability of PLA and their nanocomposites and it was found to mainly undergo random chain scission [11,12]. Surprisingly, there are only very a few reports on radiation degradation of PLA and their nanocomposites, even though it has high sensitivity to radi- ation [13]. PLA can be specially used for medical applications after radiation sterilization. In the last two decades, the main uses of PLA have been essentially limited to medical applications such as implant devices, tissue scaffolds and internal sutures and therefore, the radiation degradation study of PLA is very important at this point. To our knowledge, the durability of PLA-based nano- composites towards gamma irradiation has not reported so far. Therefore, the aim of the present paper is to investigate the effect of gamma radiation at doses ranging from 0 to 200 kGy on the structure, the morphology and the mechanical properties of PLA- C30B nanocomposites in the presence of air. The influence of C30B used as nanofiller on the durability of the nanocomposite samples is also considered. The evolution of PLA and their * Corresponding author. Tel.: þ33 2 97 87 45 84; fax: þ33 2 97 87 45 88. E-mail address: stephane.bruzaud@univ-ubs.fr (S. Bruzaud). Contents lists available at SciVerse ScienceDirect Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polydegstab 0141-3910/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymdegradstab.2012.09.014 Polymer Degradation and Stability 98 (2013) 348e355