Simultaneous Polypropylene Functionalization and Nanoclay Dispersion in PP/Clay Nanocomposites using Ultrasound Juan G. Mart  ınez-Colunga, 1 Saul S  anchez-Vald  es, 1 L. F. Ramos-deValle, 1 Libertad Mu ~ noz-Jim  enez, 1 Eduardo Ram  ırez-Vargas, 1 Maria Cristina. Ibarra-Alonso, 1 Tomas Lozano-Ramirez, 2 Pierre G. Lafleur 3 1 Centro de Investigaci  on en Qu  ımica Aplicada, Blvd. Enrique Reyna No.140 C. P. 25253 Saltillo Coahuila, M exico 2 Instituto Tecnol ogico de Cd. Madero, Juventino Rosas y Jesus Urueta, C.P. 89440 Cd. Madero, Tamaulipas, M exico 3 Ecole Polytechnique de Montreal, Chemical Engineering Department P.O Box 6079, Stn Centre-Ville, Montreal, Quebec H3C 3A7, Canada Correspondence to: J. G. Mart  ınez-Colunga (E - mail: guillermo.martinez@ciqa.edu.mx) ABSTRACT: Polypropylene nanocomposite materials were prepared with 5 and 10 wt % cloisite C20A clay, jointly with 0.6 and 1.2 wt % of maleic anhydride (MA) for the simultaneous polymer functionalization and clay dispersion in a twin screw extruder assisted with ultrasonic irradiation, using different sonication intensities (231, 347, and 462 W, which correspond to 30%, 45%, and 60% of the maximum instrument intensity, “770 W”) all in a single-step operation. The MA polymer functionalization was followed by FTIR spectroscopy and determined by titration. The increase in modulus of the obtained PP/Clay nanocomposites was attributed to the greater dispersion level, presumably achieved becuase of the joint application of the PP–Clay compatibilization with MA and the son- ication during processing in a twin screw extruder. The greater level of clay dispersion was verified by the displacement of the XRD diffraction peak to lower angles, indicating an intercalated-exfoliated structure that was corroborated by STEM. V C 2014 Wiley Periodi- cals, Inc. J. Appl. Polym. Sci. 2014, 131, 40631. KEYWORDS: composites; extrusion; grafting; nanostructured polymers; polyolefins Received 6 November 2013; accepted 21 February 2014 DOI: 10.1002/app.40631 INTRODUCTION The addition of nanofillers into a polymer matrix has given rise to a new class of materials, generally referred to as nanocompo- sites, with a notable improvement in mechanical properties mainly in modulus, heat resistance, and gas and solvent barrier, among others. 1 The effect of nanoclays as nanofillers, on the properties of different polyoleofins such as polypropylene has been intensely studied. 2 The interfacial interactions between the polyolefin chains and the clay layers play an important role because the final structure of the nanocomposite depends on these interactions, which play an important role in achieving an exfoliated or intercalated structure. 3 The exfoliation of the nor- mally aggregated-stacked structures of montmorillonite (tactoids) during polymer processing, is highly difficult. Becuase of their relatively large size, and their incompatibility towards polyolefines, these tactoids induce local tensions when the polymer-clay nanocomposites are deformed, and as a result the elongation at break and the impact strength become very low. Therefore, compatibilization and dispersive mixing are of the utmost importance in order to achieve the best mechanical properties in the nanocomposite. 4 Maleic anhydride (MA)- modified polypropylene is commonly used as compatibilizing agent. 5–8 This chemical modification adds polar groups to poly- olefins, resulting in reactive centers that increase polymer–filler or polymer–polymer interfacial interaction. 9,10 The selection of the monomer to be grafted into the polyolefin, which will gen- erate the compatibilizing agent, should be done considering that it must have unsaturations, polar groups and be stable at the functionalization reaction temperatures. The most used mono- mers for the PP modification are acrylic acid, MA, Zigler-Natta catalysts, borane derivatives, 11 esters, and carboxylic acids, 12 although the most reported moiety is the MA 13–19 . The grafting of MA to polyolefins is usually performed in the extruder, using peroxide as an initiator. 20–36 On the other hand, the modifica- tion of polypropylene with MA, via extrusion with the assis- tance of ultrasonic irradiation, has also been reported. 37 The presence of fillers in the PP matrix provides a substantial increase in the modulus and thermal resistance, as well as on V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2014, DOI: 10.1002/APP.40631 40631 (1 of 8)