Surface characterization of polyethylene terephthalate/silica nanocomposites Mazeyar Parvinzadeh a, *, Siamak Moradian b , Abosaeed Rashidi a , Mohamad-Esmail Yazdanshenas c a Department of Textile, Islamic Azad University, Science and Research Branch, Tehran, Iran b Department of Polymer and Color Engineering, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Iran c Department of Textile, Islamic Azad University, Yazd Branch, Yazd, Iran 1. Introduction Polymeric nanocomposites are a class of materials in which nanoscale particulates such as layered clays or spherical inorganic minerals are dispersed within polymeric matrices. Compared to pure polymers, polymeric nanocomposites are claimed to exhibit markedly improved properties, such as modulus, strength, stiffness, flame retardancy, dimensional stability, electrical con- ductivity, barrier performance, solvent and heat resistance, wettability and dyeability depending on type and content of nanoparticles used [1–6]. Processing of such polymeric nanocomposites are more difficult compared to the corresponding pure polymers since such inorganic nanoparticles have strong tendencies to agglomerate. To overcome such difficulties, use is made of sol–gel processing, in situ polymerization and melt compounding. The last method is still the most cost effective, simple, feasible and environmentally benign process for the mass production of polymeric nanocompo- site [7–10]. Poly(ethylene terephthalate) (PET) is a semicrystalline polymer and its composites are widely used in packaging, construction, automobile, household, electrical and textile industries. Consider- able efforts have been devoted to improve various physical, mechanical and barrier properties of PET through mixing it with nanoclays to produce layered clay-incorporated PET composites [11–23,10,24–29]. Other approaches for improving such proper- ties are incorporation of spherical inorganic nanoparticles such as nano-SiO 2 into the PET matrix [30–38]. Fumed silica is characterized by its extremely small particle size and large surface area. The surface of fumed silica has three chemical groups of isolated hydroxy, hydrogen-bonded hydroxy, and siloxane groups. Thus, the surface generally is hydrophilic, although the siloxane groups are hydrophobic. The hydrophilic surface of fumed silica, however, can be rendered hydrophobic by reacting its surface hydroxyl groups with hydrophobic reagents such as polydimethylsiloxane, dimethyldichlorosilane and hex- amethyldisilane [39]. Many research works have focused on incorporation of nano- silica into various polymers however only a few deal with preparation of PET-silica nanocomposites [30–38,40–52]. Researchers claim that nano-silica particle impact higher stiffness, tensile strength, mod- ulus, impact strength, toughening, crystallinity, viscosity, creep resistance, and interfacial adhesion in polyethylene, polypropylene and thermoplastic elastomer nanocomposites, depending on surface properties of such nano-silica particles [40,42,44–46,48–50]. The addition of different nano-silica particles improves coefficient of friction, wear resistance and toughness of nylon 6 and nylon 6,6 nanocomposites [43,51]. Polyvinyl alcohol–SiO 2 interactions highly influenced the composite and particle distribution within the polymer matrix depending on pH of solution [41,47]. In the case of PET nanocomposites, experimental evidence indicates that nano-silica does not behave as a nucleating agent Applied Surface Science 256 (2010) 2792–2802 ARTICLE INFO Article history: Received 27 April 2009 Received in revised form 7 November 2009 Accepted 11 November 2009 Available online 17 November 2009 Keywords: PET Nano-silica Hydrophilic Hydrophobic ABSTRACT Poly(ethylene terephthalate) (PET) based nanocomposites containing hydrophilic (i.e. Aerosil 200 or Aerosil TT 600) or hydrophobic (i.e. Aerosil R 972) nano-silica were prepared by melt compounding. Influence of nano-silica type on surface properties of the resultant nanocomposites was investigated by the use of Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement (CAM), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). The possible interaction between nano-silica particles and PET functional groups at bulk and surface were elucidated by transmission FTIR and FTIR-ATR spectroscopy, respectively. AFM studies of the resultant nanocomposites showed increased surface roughness compared to pure PET. Contact angle measurements of the resultant PET composites demonstrated that the wettability of such composites depends on surface treatment of the particular nano-silica particles used. SEM images illustrated that hydrophilic nano-silica particles tended to migrate to the surface of the PET matrix. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +98 9123137115; fax: +98 2122593135. E-mail address: mparvinzadeh@gmail.com (M. Parvinzadeh). Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc 0169-4332/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.11.030