Research paper Influence of clay mineral structure and polyamide polarity on the structural and morphological properties of clay polypropylene/ polyamide nanocomposites Quentin Beuguel, Julien Ville, Jérôme Crepin-Leblond, Pascal Mederic, Thierry Aubry ⁎ IRDL – FRE CNRS- 3744, Université de Bretagne Occidentale – UFR Sciences et Techniques, 6 avenue Victor le Gorgeu – CS 93 837, 29 238 Brest Cedex 3, France abstract article info Article history: Received 14 July 2016 Received in revised form 28 September 2016 Accepted 29 September 2016 Available online xxxx The influence of the clay mineral structure and of the polyamide dispersed phase polarity on the structure and morphology of polypropylene/polyamide blends filled with clay mineral nanoparticles was investigated. Two polyamides (PA) were used: a polar PA6 and a less polar PA12. The clay mineral nanofillers used were either or- ganically modified montmorillonite (Mt) or synthetic talc (ST), having preferential affinity towards PA dispersed phase. For all clay polymer nanocomposites (CPN), a decrease of PA nodule size was observed. However, the mechanisms governing the morphology establishment were shown to depend mainly on the clay structure, and also on the polyamide polarity. Mt nanoparticles were shown to be mostly located at the interface, forming a nanocomposite interphase. The decrease of PA nodule size induced by Mt nanoparticles was attributed to coa- lescence inhibition by steric repulsions, mediated by the interphase, which is more developed in the case of PA6. Besides, the interphase was shown to play a key role in the change from a nodular to a non-nodular morphology, even at low Mt fractions. ST particles were shown to be exclusively dispersed within PA nodules. In this case, nod- ule size reduction was attributed to the presence of some larger ST particles, exhibiting numerous structural de- fects, which favor the nodule break-up, especially in the case of PA12. © 2016 Elsevier B.V. All rights reserved. Keywords: Synthetic talc Montmorillonite Polypropylene/polyamide blends Structure Morphology 1. Introduction Since a few decades, immiscible thermoplastic blends have attracted interest of scientific and industrial communities (Utracki, 1998). In this context, polypropylene (PP) and polyamide (PA) blends have been thoroughly investigated because they combine the thermomechanical properties of polyamide and the easy processing characteristics of poly- propylene. Blend properties depend on the composition and on the morphology, either nodular, fibrillar, lamellar or co-continuous (Huitric et al., 1998), formed during melt mixing process. The shape and size of the dispersed phase result from a competition between break-up and coalescence during mixing (Serpe et al., 1990). The visco- elastic properties of the two components play a key role in the establish- ment of the morphology (Starita, 1972; Grace, 1982). Addition of a compatibilizing agent is most often used in order to get a fine dispersion, to stabilize the blend morphology, and to improve in- terfacial adhesion. A macromolecular compatibilizer, either a block or a graft copolymer, is classically used, leading to a decrease of the interfa- cial tension (Moan et al., 2000) and an enhancement of interfacial adhe- sion (Xanthos and Dagli, 1991). More recently, a considerable scientific interest has focused on the influence of nanoparticles on the morphology establishment of immiscible polymer blends as shown by the numerous references cited in the paper by Salzano de Luna and Filippone (2016). In this context, clay nanolayers, mainly from the fam- ily of organically modified montmorillonite (Mt), have been successful- ly chosen to play the role of compatibilizing agent (Ray et al., 2004; Hong et al., 2006). Indeed, when Mt nanoparticles are located at the ma- trix/nodule interface, they form a nanocomposite interphase, which leads to the refinement and stabilization of the morphology (Huitric et al., 2009). The interphase, which exhibits numerous defects (Ville et al., 2012; Labaume et al., 2013), inhibits coalescence by steric repulsion (Gahleitner et al., 2006; Ville et al., 2012; Labaume et al., 2013; Huang et al., 2014), but it destabilizes the nodular morphology of the polyethyl- ene/polyamide blends at low clay fractions (Labaume et al., 2013). However, Mt. nanoparticles are not systematically located at the inter- face in Mt/polymer nanocomposites (Yoo et al., 2005; Gahleitner et al., 2006; Labaume et al., 2013; Huang et al., 2014). Indeed, clay localization depends on the affinity of nanofillers towards the two polymers (Sumita et al., 1991), on the rheological behavior of both thermoplastic phases (Labaume et al., 2013), and on intrinsic properties of the parti- cles, such as aspect ratio (Médéric et al., 2011) and flexibility (Fu et al., 2011). The presence of clay nanoparticles within dispersed phase or matrix is known to strongly influence the mechanisms of morphology establishment (Yoo et al., 2005). On the one hand, the dispersion of nanoclay within the matrix enhances nodule size reduction (i) by Applied Clay Science xxx (2016) xxx–xxx ⁎ Corresponding author. E-mail address: thierry.aubry@univ-brest.fr (T. Aubry). CLAY-04004; No of Pages 7 http://dx.doi.org/10.1016/j.clay.2016.09.034 0169-1317/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Please cite this article as: Beuguel, Q., et al., Influence of clay mineral structure and polyamide polarity on the structural and morphological properties of clay polypropylene/po..., Appl. Clay Sci. (2016), http://dx.doi.org/10.1016/j.clay.2016.09.034