A Surface Analysis of Polypropylene/Clay Nanocomposites Exposed to Electron Irradiation Ahmad Asadinezhad, 1 Hossein Ali Khonakdar, 2 Seyed Hassan Jafari, 3 Frank Simon, 4 Udo Wagenknecht 4 1 Department of Chemical Engineering, Isfahan University of Technology, 84156-83111, Isfahan, Iran 2 Department of Polymer Processing, Iran Polymer and Petrochemical Institute, 14965-115, Tehran, Iran 3 School of Chemical Engineering, College of Engineering, University of Tehran, 11155-4563, Tehran, Iran 4 Leibniz-Institut fu ¨r Polymerforschung Dresden e.V., D-01069, Dresden, Germany Correspondence to: H. A. Khonakdar (E-mail: hakhonakdar@gmail.com) ABSTRACT: The effects of electron irradiation in air at various doses on surface chemical composition of nanofilled polypropylene were explored by X-ray photoelectron spectroscopy. An organically modified nanoclay ingredient along with a functional compatibil- izer was employed for this purpose. The nanocomposite formation was confirmed by means of transmission electron microscopy, where in presence of compatibilizer, an exfoliated structure was brought about. Medium irradiation dose was established to be con- siderably effective in raising surface oxygen content, while at very high electron beam fluence, the ablation (etching) predominated. The optimal electron beam intensity was also found with respect to the extent of the functionalization. Various moieties of ether, ester, and alcohol characteristics were produced after exposure which could act as functional, active precursors being suitable for subsequent functionalization reactions. Furthermore, it could be understood that the electron irradiation spur organoclay migration toward surface layers. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000–000, 2012 KEYWORDS: surfaces and interfaces; irradiation; nanostructured polymers Received 7 June 2012; accepted 6 July 2012; published online DOI: 10.1002/app.38314 INTRODUCTION The properties of the polymer surfaces are largely controlled by chemistry of the surface layer. A number of techniques have been devised to tune and analyze materials surfaces and found many benefits in different applications. 1 The surface modifica- tion of polymers by means of ionizing radiation has been known for decades and yet is a subject of intensive research. 2 Irradiation brings on a series of chemical reactions involving functionalization, crosslinking, and etching which all occur at the surface to the extent depending on the irradiation dose and the working gas. As the penetration depth of the ionizing beam is on the order of micrometers, only the near-surface region (top nanolayer) is modified and the bulk remains unchanged. 3 The outcome of the surface modifications can then be exploited in many applications such as biomedical ones. Recently, several homopolymers have been improved in per- formance thanks to the incorporation of the active, nanofillers. 4 This also holds for polypropylene (PP), where due to the inher- ent incompatibility with some nanoparticles, an interfacial modifier is occasionally employed to increase phase adhesion. PP/Clay nanocomposites which are esteemed nowadays as novel materials of successful performance, 5 suffer from undesired sur- face properties such as low affinity toward synthetic/natural entities. This can be dealt with somewhat via irradiation techni- ques. Few reports have yet been devoted to surface modification of the nanofilled polymers. 6–9 Poly(carbonate-urea) urethane copolymer films were treated via plasma in oxygen and increased adhesion, coverage, and growth of human umbilical vein endothelial cells were demonstrated. 6 Also, UV irradiation of the same material revealed that the adhesion and prolifera- tion of the human umbilical vein endothelial cell line was con- siderably promoted upon irradiating with UV rays under nitro- gen and oxygen ambient. 7 The UV exposure changed the surface from amphiphilic to hydrophilic while preserving the morphol- ogy. Elsewhere, 8 argon ion bombardment on the surface of car- bon-titanium nanocomposite films was performed and observed that after the ion bombardment, the oxygen atoms were selec- tively bonded to titanium atoms. Also, a preferential sputtering of the amorphous phase was detected leading to the emergence of carbon/titanium nanocrystallites on film surface. The oxygen plasma treatment of nanocomposite hybrid polymer thin films V C 2012 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM WILEYONLINELIBRARY.COM/APP J. APPL. POLYM. SCI. 2012, DOI: 10.1002/APP.38314 1