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  • rmyle

    a a b a,

    evelopminagar,

    a r t i c l e i n f o

    Article history:Received 17 September 2010Accepted 14 November 2010

    nd application in exible magnetic devices, magneto- composites comprising of nano particles of Fe2O3 andpolyaniline have been demonstrated to reduce the dielec-tric loss and dielectric permittivity to achieve maximalabsorption of electromagnetic energy [12]. In order togenerate magnetic susceptibility along with high temper-ature resistance, polymer nanocomposites require addition

    * Corresponding author. Tel.: 91 512 2451759 78x467; fax: 91 5122450404.

    E-mail address: dksetua@rediffmail.com (D.K. Setua).

    Contents lists available at ScienceDirect

    Polymer T

    journal homepage: www.else

    Polymer Testing 30 (2011) 155160concentration from 0% to 10wt. % of g-Fe2O3. Themagnetic nanocomposites, in general, alsoshowed very good mechanical strength and high temperature resistance.

    2010 Elsevier Ltd. All rights reserved.

    1. Introduction

    Recent years have witnessed a rapid growth in thedevelopment of smart materials and devices consisting ofpolymers and elastomers carrying magnetically polarizableparticles e.g., iron [1]. Composites based on ferromagneticor superparamagnetic nanoparticles in polymers can

    rheological (MR) elastomers, active vibration dampingmaterials, magnetic recording media, conductive seals/gaskets etc for missiles [29]. Composites to be used inthese components/devices should have good mechanicalstrength and high temperature resistance. The relationshipbetween microstructure of iron particles and the MR effectin elastomers has been reported [10,11]. ConductingKeywords:Magnetic polymer nanocompositePolypheylene oxideg-Fe2O3Vibrational sample magnetometerSEM-EDXThermal analysis0142-9418/$ see front matter 2010 Elsevier Ltddoi:10.1016/j.polymertesting.2010.11.009a b s t r a c t

    Nanocomposites of polyphenylene oxide (PPO) lled with nanoparticles of organicallymodied g-Fe2O3, in varied concentration from 0 to 20 wt. %, were prepared. Thermalstability of these nanocomposites was evaluated by thermo-gravimetric analysis (TGA) andtheir dimensional stability was measured at sub-ambient as well as at elevated tempera-tures by thermo-mechanical analysis (TMA). The glass transition temperature (Tg) of thenanocomposites, measured by differential scanning calorimeter (DSC), was found todecrease with increasing weight fraction of g-Fe2O3. Phase morphology of the nano-composites was analyzed by scanning electron microscope (SEM). The distribution ofg-Fe2O3 in PPO matrix was studied by determining the iron using a X-ray energy dispersivespectroscope (EDX) attached to the SEM. These analyses reveal that the nanoparticles ofg-Fe2O3with an average diameter of 20 nmwere dispersed uniformly in the PPOmatrix andalso that there was very good matrix-ller adhesion. A detailed morphological study usinga Gatan hot stage attachment with the SEM showed that there was no change in the surfacemorphology from ambient to high temperature up to 280 C, beyond which segregation ofthe nanoparticles took place. Measurements by vibrational sample magnetometer (VSM)showed that the degree of saturation magnetization increased with increasing lleraDefence Materials and Stores Research and DbDefence Institute of Advanced Technology, Girent Establishment, DMSRDE (Post Ofce), G. T. Road, Kanpur 208013, IndiaPune 411025, IndiaK. Agarwal , M. Prasad , R.B. Sharma , D.K. Setua *Material Properties

    Studies on Microstructural and Thenanocomposite based on polypheniron oxide. All rights reserved.ophysical properties of polymerne oxide and Ferrimagnetic

    esting

    vier .com/locate/polytest

  • coated with a suitable organic surfactant and their homo-

    determine the glass transition temperature (Tg) of thecomposites at heating rate of 20 C/min and temperaturerange from150 C to 50 C using a liquid nitrogen coolingaccessory. 510 mg of a sample was put in a platinum panand heated from ambient to 800 C at a constant rate

    ngation atak (Eb), %

    Peak degradationtemperature, C

    Glass transitiontemperature(Tg), C

    1 480.9 208.00 479.2 205.85 477.1 202.51 475.7 196.36 471.1 184.71 469.7 163.72 468.7 154.9

    K. Agarwal et al. / Polymer Testing 30 (2011) 155160156geneous dispersion in PPO matrix was obtained by select-ing appropriate polymer processing techniques.

    2. Experimental details

    g-Fe2O3 with an average particle size of 20 nm wassupplied by Macwin Pvt. Ltd., New Delhi, India. PPO (grade803) was obtained from GE plastic, Bangalore, India. Thesurface of the ller particles were coated with organicnonionic surfactant Sorbitol-monoleate gel (PH: 7, g-Fe2O3:gel 1:1 wt. ratio) at room temperature (252 C) by trit-urating with a pestle and mortar for about 15 min. Theagglomerates/lumps of g-Fe2O3 were broken into nepowder and a homogeneous paste of the g-Fe2O3 in sorbitolgel was obtained. The composites containing 1,2,3,5, 10 &20 wt. % of the modied g-Fe2O3 were prepared in a micro-compounder (model Haake Mini Lab-II of ThermoscienticCo., Karlsruhe, GmbH,Germany)with amini-extruder usingconical intermeshing co-rotating screws at 280 C for 5min.of magnetic nanollers to high temperature resistantpolymers. The polymer should also enable proper disper-sion of the nanoparticles in the matrix as well as very goodpolymer-ller adhesion to prevent agglomeration of theller particles during processing or annealing/storage ofthe polymer/elastomer compounds. Modication of thesurface of the iron particles by surfactants e.g., by use ofsilane coupling agents, has also been reported to benecessary for proper polymer-ller interactions andimprovement of the tensile strength of the composites [13].

    Poly(p-phenylene oxide)(PPO) is a high temperatureengineering thermoplastic stable up to 400 C and hasa high glass transition temperature (Tg 210 C). It has,therefore, been chosen to prepare conducting polymernanocomposites by addition of nanosized Maghemiteg-Fe2O3 [1416]. The surfaces of g-Fe2O3 particles were

    Table 1Mechanical and Thermal properties of the Nanocomposites.

    Sample Tensile strength(Ts), MPa

    Elobre

    Neat PPO 68.5 15.PPO: g-Fe2O3 (100:1) 71.5 15.PPO: g-Fe2O3 (100:2) 72.1 13.PPO: g-Fe2O3 (100:3) 73.0 12.PPO: g-Fe2O3 (100:5) 75.2 11.PPO: g-Fe2O3 (100:10) 75.6 11.PPO: g-Fe2O3 (100:20) 74.5 10.The processing conditions were optimized to achieveuniform dispersion of the nanoparticles in the polymermatrix as cross checked by SEM. A micro injection moldingmachine (Type 557-2286) of Thermoscientic Co.,Germany was used to prepare tensile dumb-bell specimenswith temperature of the cylinder at 280295 C, holdingtime 20 s and injection pressure of 1000 bar in molds keptat 80100 C. Both the tensile strength (TS) and elongationat break (Eb) of the samples were measured in a UniversalTesting Machine (UTM, Model H10 kS, Tinius Olsen, UK) atstrain rate of 10 mm/min at room temperature. A DSC 2910(TA Instruments Inc., New Castle, NJ, USA) was used toof 20 C/min in nitrogen gas purge of 60 ml/min in aHi-Resolution TGA 2950 (TA Instruments Inc., USA) formeasurement of thermal stability. For dimensional stabilityof the composites, a TMA 2940 (TA Instruments Inc., USA)with an expansion probe was used and samples of size4 4 mm and thickness 4 0.01 mmwere heated at a rateof 5 C/min from 5 C to 150 C. Phase morphology of thenanocomposites was evaluated using a Carl Zeiss EVO 50Scanning Electron Microscope (SEM). The cross-section ofthe tensile fractured surfaces of the samples, without anygold coating, was used. For elemental analysis of thenanoparticles present on the fracture surface, X-ray energydispersion spectroscopy (EDX, Genesis 2000) attached tothe SEM was utilized. A vibrational sample magnetometerEV7-VSM (ADE-DMS, USA) was used to determine themagnetic properties of the samples. In VSM, the sampleunder study was kept in a constant magnetic eld tomagnetize the sample by aligning the magnetic dipoles orthe individual magnetic spins of the magnetic particlesalong the direction of the applied magnetic eld. Thestronger the applied eld, the larger is the magnetization.As the sample is moved up and down, this magnetic strayeld is also changed and can be sensed by a set of pick-upcoils. The alternating magnetic eld will cause an electriceld in the pick-up coils resulting in variation of theinduction current (I) proportional to the extent ofFig. 1. TGA Thermograms of Polypheylene oxide with 10 wt.% of g-Fe2O3.

  • not signicant beyond 5 wt% of g-Fe2O3. This is because of

    supportive of our earlier reports on different polymer-

    -3

    -2

    -1

    0

    Hea

    t Flo

    w (W

    /g)

    -40 50 100 150 200 250 300 350 400

    Exo Up

    (a)

    (b)

    (c)

    (d)

    (e)

    (f)

    (g)

    Temperature (C)

    Fig. 2. DSC overlay of PPO nanocomposites, (a) Neat PPO, (b) 1 wt.% ller, (c)2 wt.% ller, (d) 3 wt.% ller, (e) 5 wt.% ller, (f) 10 wt.% ller and (g) 20 wt.%ller.

    Fig. 4. SEM Photographs of Phase Morphology of the Neat PPO.

    K. Agarwal et al. / Polymer Testing 30 (2011) 155160 157saturation of the ller surface by bound polymer chains andformation of a stagnant polymeric thin lm encapsulatingmagnetization of the sample. This was then amplied bya trans-impedance lock-in amplier and measured.

    3. Results and discussion

    Values of Ts and Eb, degradation peak temperature andTg measured by UTM, TGA and DSC, respectively, are givenin Table 1. PPO lled with g-Fe2O3 shows enhancement ofTs up to 10 wt. % but it is then reduced at 20 wt. %. However,the Eb has been found to be reduced consistently due toller addition from 1 to 20 wt. %. The lowering of Eb isbecause of increasing hardness and adherence of themacromolecular chains to the surface of the nanoparticlesby polymer- ller interaction and, thereby,

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