Nanocomposites of Silica Reinforced Polypropylene: Correlation Between Morphology and Properties Amira Bouaziz, 1,2 Mohamed Jaziri, 1 Florent Dalmas, 3 Valerie Massardier 2 1 Laboratoire d’Electrochimie et Environnement, ENIS-Sfax, 3038 Sfax, Tunisie 2 INSA de Lyon, CNRS UMR 5223, Ing  enierie des Mat  eriaux Polyme ` res, Villeurbanne, F-69622 Lyon, France 3 ICMPE (Institut de Chimie et des Mat  eriaux Paris-Est), UMR 7182 CNRS/Universit  e Paris-Est Cr  eteil, 2-8 rue Henri Dunant, 94320 Thiais, France Polypropylene/fumed hydrophilic silica nanocomposites were prepared via melt mixing method using a single- screw extruder. Comparative study with and without compatibilizing copolymer agent (maleic anhydride grafted polypropylene: PP-g-AM) was conducted. The obtained results were interpreted in terms of silica nanoparticle–silica nanoparticle and silica nanoparticle-polymer interactions. These results have shown that the addition of nanofillers improves the prop- erties of the nanocomposites. From transmission elec- tron microscopy, it was found that agglomerations of silica particles into the PP matrix increased in average size with increasing silica contents, except in presence of the copolymer. Storage modulus values of the nano- composites measured by dynamic mechanical thermal analysis were sensitive to the microstructure of the nano- composites. Higher silica contents resulted in higher storage modulus, revealing that the material became stiffer. By adding the compatibilizer, a further increase of storage modulus was observed due to the finer disper- sion of the filler in the matrix and the increased interfacial adhesion. Crystallization rates were found to increase with the increase of silica nanoparticles as well as PP-g- MA content. In addition, silica nanoparticles and the compatibilizing agent present centers of germination and nucleation of crystallites. Thus, the use of the coupling agent resulted in a further enhancement of mechanical properties of the nanocomposites due to the reduction of silica agglomeration. POLYM. ENG. SCI., 54:2187–2196, 2014. V C 2013 Society of Plastics Engineers INTRODUCTION Over the past decades, there has been a notable progress in the science and technology of polymer nanocomposites. This innovative class of materials made up of organic polymer composites with inorganic nanoscale building blocks combines the advantages of the inorganic material (e.g., rigidity, thermal stability) and the organic polymer (e.g., flexibility, dielectric, ductility, and processability). Furthermore, nanocompo- sites usually exhibit superior mechanical performance and improved physical properties at very low loading levels compared to pristine polymer or conventional filler composites due to the presence of nanometer range dispersion in the former and the dramatic increase in interfacial area, which creates a significant volume fraction of interfacial polymer. Typical filler amounts of less than 5 wt% result in effective enhancement of the nanocomposite [1]. Whether in solution or in bulk, these materials offer unique mechanical, electrical, optical, thermal, and gas barrier properties [1–10]. Such enhancements are induced by the physical presence of the nanoparticles, the interac- tion of the polymer with the particle and mainly by the state of dispersion [1, 2, 6, 7]. A variety of polymer matrices was used for the prepa- ration of up to date nanocomposites. They are divided into two categories: thermoplastic matrices such as poly- vinyl chloride, polyethylene [10], polystyrene (PS) [11], polyamide (PA), polycarbonate, and thermosetting matri- ces such as unsaturedpolyester [12] and epoxy resins [13]. Isotactic polypropylene (iPP) is a versatile thermoplas- tic polymer, one of the most widespread commodities due to its low price and balanced properties. It is nontoxic, nonallergenic, chemically inert, and recyclable with a rel- atively low melting point. Correspondence to: Valerie Massardier; e-mail: valerie.massardier@insa- lyon.fr Florent Dalmas is currently at MATEIS (Mat eriaux: Eng enierie et Sci- ence), UMR 5510 CNRS/INSA de Lyon, B^ at. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne cedex, France. DOI 10.1002/pen.23768 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2013 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—2014