Thermochimica Acta 433 (2005) 187–195 Clay intercalation and inﬂuence on crystallinity of EVA-based clay nanocomposites D.S. Chaudhary, R. Prasad, R.K. Gupta, S.N. Bhattacharya ∗ Rheology and Materials Processing Centre, School of Civil and Chemical Engineering, RMIT University, 124 La Trobe St., Melbourne 3000, Australia Received 7 December 2004; received in revised form 4 February 2005; accepted 14 February 2005 Available online 26 April 2005 Abstract Various polymer clay nanocomposites (PCNs) were prepared from ethylene vinyl acetate copolymer (EVA) with 9, 18 and 28% vinyl acetate (VA) content ﬁlled with different wt.% (2.5, 5 and 7.5) of a Montmorillonite-based organo-modiﬁed clay (Cloisite ® C15A and C30B). The PCNs were prepared using melt blending techniques. Morphological information regarding intercalation and exfoliation were determined by using wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). WAXS and TEM conﬁrmed that increasing the VA content was necessary to achieve greater clay–polymer interaction as seen from the comparatively higher intercalation of clay platelets with 28% VA. The effect of addition of clay on the development and the modiﬁcation of crystalline morphology in EVA matrix was also studied using WAXS and temperature-modulated differential scanning calorimetry (MDSC). Results are presented showing that the addition of clay platelets does not increase the matrix crystallinity but the morphology was signiﬁcantly modiﬁed such that there was an increase in the ‘rigid’ amorphous phase. Mechanical properties were also evaluated against the respective morphological information for each specimen and there are indications that the level of clay–polymer interaction plays a signiﬁcant role in such morphological modiﬁcation, and in such a way that affects the ﬁnal PCN mechanical properties which has wide and signiﬁcant applications in the packaging industries. © 2005 Elsevier B.V. All rights reserved. Keywords: EVA; Nanocomposites; Mechanical; Morphology; MDSC 1. Introduction The combination of ethylene vinyl acetate (EVA) with nanoclay has wide commercial applications (such as packag- ing ﬁlms, cables and adhesives), and these applications de- pend on the vinyl acetate (VA) contained in the main chain. As the VA content increases, the copolymer presents increasing polarity but lower crystallinity, and therefore different me- chanical behavior [1]. The increasing polarity with increasing VA content is apparently useful in imparting a high degree of polymer–clay surface interaction, and it has been reported that there is a signiﬁcant rise in the Young’s modulus and the yield strength of the EVA PCNs [2], in tune with the behavior of other polymeric nanocomposites [3]. ∗ Corresponding author. Tel.: +61 3 992552086; fax: +61 3 99252268. E-mail addresses: deeptangshu@hotmail.com (D.S. Chaudhary), sati.bhattacharya@rmit.edu.au (S.N. Bhattacharya). This study is aimed at producing EVA nanocomposites us- ing matrices with various VA content and clay concentrations, and analyzing them for their respective clay–polymer inter- action and their inﬂuence on the phase modiﬁcation (matrix crystallinity) and mechanical properties. Since the VA con- tent dictates the polarity of the matrix – thus dictating the level of organoclay–polymer interaction – morphologies of EVA nanocomposites would differ based on VA content and their interaction with its nanoclay content. For example, some authors have reported how the structure–mobility properties of EVA polymer are inﬂuenced by the VA content [4] and this chain mobility in and around clay galleries could signiﬁcantly modify the level of interaction in clay nanocomposites. Also, it is well known that inclusion of ﬁller provides a suitable pathway for increased crystallinity and consequently higher crystallization temperatures in polymeric samples because of the nucleation effects of the ﬁllers (by providing active surface structures) [5]. However, presence of small quan- 0040-6031/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tca.2005.02.031