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Effects of nano  -Al2O3 fillers and dispersant on thermal and dynamic mechanical properties of polypropylene/nano  -Al2O3 composite

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Effects of nano  -Al2O3 fillers and dispersant on thermal and dynamic mechanical properties of polypropylene/nano  -Al2O3 composite
Transcript  Composite MaterialsJournal of Thermoplastic online version of this article can be found at: DOI: 10.1177/0892705711421805November 2011 2012 25: 453 srcinally published online 21 Journal of Thermoplastic Composite Materials  F Mirjalili, L Chuah, M Khalid and M Hasmaliza  composite3O2-Al α mechanical properties of polypropylene/nano fillers and dispersant on thermal and dynamic3O2-Al α Effects of nano Published by: at: can be found Journal of Thermoplastic Composite Materials  Additional services and information for Email Alerts: Subscriptions: Reprints: Permissions: Citations:  What is This? - Nov 21, 2011OnlineFirst Version of Record - Nov 29, 2011OnlineFirst Version of Record - May 16, 2012Version of Record >>  at Universiti Putra Malaysia on May 17, 2012 jtc.sagepub.comDownloaded from    Article Effects of nano   -Al 2 O 3 fillers and dispersant onthermal and dynamicmechanical propertiesof polypropylene/nano  -Al 2 O 3  composite F Mirjalili 1 , L Chuah 2 , M Khalid 3 and M Hasmaliza 4 Abstract This article presents a comparative study on the effects of nano  a -alumina on thermaldegradation and dynamic mechanical properties of polypropylene (PP) nanocomposites.In this respect, two types of composites were prepared, with dispersant and withoutdispersant. Thermogravimetric analysis of both composites showed a drastic shift in theweight loss curve toward higher temperature, which led to reduction in the PP heatrelease rate in both composites. Differential scanning calorimetry results showed thatthe crystallinity of the nanocomposites was increased especially in the presence of dispersant. The storage modulus of the nanocomposites was found to be higher thanthat of pure PP, because nanofiller increased the stiffness of the nanocomposites. Theglass transition temperatures of the nanocomposites were not significantly changed anddamping factor of the nanocomposites was decreased. Keywords a -nano alumina, polypropylene, thermogravimetric, storage modulus, nanocomposite 1 Maybod Branch, Islamic Azad University, Maybod, Iran 2 Department of Chemical & Environmental Engineering, University Putra Malaysia, Malaysia 3 Department of Biotechnological and Biochemical Engineering, International Islamic University Malaysia, KualaLumpur, Malaysia 4 School of Material & Mineral Resources Engineering, University Sains Malaysia, Malaysia Corresponding author: F Mirjalili, Maybod Branch, Islamic Azad University, Maybod, IranEmail:  Journal of Thermoplastic CompositeMaterials25(4) 453–467 ª The Author(s) 2011Reprints and 10.1177/0892705711421805  at Universiti Putra Malaysia on May 17, 2012 jtc.sagepub.comDownloaded from   Introduction Polymeric nanocomposites have been recently established as an existing new classof materials filled with particles of at least one dimension in the nanosized range(1–100 nm). These nanocomposites exhibit superior mechanical performance and improve the barrier properties at very low loading levels compared to conventional filler composites. Improvement on mechanical properties, such as stiffness and toughness,dimensional, barrier and thermal properties, are usually observed. 1,2 However, there areseveral key issues in the fabrication of polymer nanocomposites that should be carefullytaken into account. These issues include uniform dispersion of nanoparticles against their agglomeration due to Vanderwaals bonding, alignment of nanofiller in the matrix,volume fraction, manufacturing rate and cost. 3 To improve the dispersion and interfacial properties of the polymer nanocomposites, there are at least two ways in practice.The first one is to treat the surface of nanoparticles and the second one is to modify thesurface properties of polypropylene (PP). 4 Most of the oxide fillers are hydrophilic innature, whereas many polymers including PP are hydrophobic. Dissimilarity of the surface chemistry between the filler and polymer contributes to the decrease in thetensity of filler–polymer systems. Widely used reactive coupling agents are silans and titanates categories. In general, titanium oxide can be represented as O ¼ T ¼ O, and thisunsaturated characteristic is expected to react with hydroxyl groups on the surface of inorganic fillers to give hydrophobic polymer–compatible monomolecular layers. 5 Accordingly, they promote adhesion, improve dispersion, lower viscosity, and prevent phase separation. The introduction of active groups onto nanoalumina surfaces wasachieved by the reaction shown in Figure 1.Among commodity thermoplastics, PP is characterized by light weight, low cost, easy processing, high mechanical strength, excellent chemical stability and excellent elec-trical properties. 6 In this research nano a -Al 2 O 3  was chosen as the filler due to its specialcombined chemical and physical properties such as excellent resistance to heat and wear,high specific strength and good oxidation resistance. In composite systems, dynamic properties such as damping behavior and thermal properties such as thermal stability and thermal expansions and crystallization kinetics are very important factors that affect thequality of the final products. 4 Figure 1.  Schematic illustration of the reaction between titanium oxide and the hydroxyl groupsof nanoalumina. 454  Journal of Thermoplastic Composite Materials 25(4)  at Universiti Putra Malaysia on May 17, 2012 jtc.sagepub.comDownloaded from   In this work, sodium dodecyl benzenesulfonate was used as dispersant for the surfacetreatment of nano  a -Al 2 O 3 .The effects of dispersant on the thermal and dynamic behavior of PP/nano  a -Al 2 O 3  composites were investigated. Materials and methods Materials The PP grade 600G (melting temperature and melt flow rate are 165  C and 11 g/min, itsdensity is 900 kg/cm 3 ) used in this work was supplied by Petronas Polymers Marketingand Trading Division Malaysia. Nano  a -Al 2 O 3  with the average particle size of 20–30 nm and density of 3106 kg/m 3 was used. These nanoparticles were made in thelaboratory by the procedure discussed by Mirjalili et al. 7 Titanium dioxide (TiO 2 ) powder with a minimum assay of 98 % used as a coupling agent was supplied from Fisher Chemicals Sdn. Bhd., Malaysia. Sodium dodecylbenzene sulfonate (SDBS) purchased from Merck (Germany) was used as a dispersant. Surface treatment of nano  a -Al  2 O 3 Ultrasonication(KQ2200DEUltrasonicCleanser,100W,KunshanofJiangsuEquipmentCompany, China) was used for preparation of miscellaneous aqueous nano-suspensions,which is a conventional method for dispersing the extremely entwined or aggregated nanoparticle samples. About 0.1 g alumina nanoparticle and water solution (99.8 g) withananionsurfactant(0.1gSDBS)weredirectlymixedina150-mlbeaker.Thesuspensionwas sonicated for 1 h and was dried at 80  C for 4 hours. Preparation of PP/nano  a -Al  2 O 3  composites samples All materials used for preparation of PP/nano  a -Al 2 O 3  were weighted and listed in theTable 1.Predrying process was carried out on the nano  a -Al 2 O 3  at 80  C for 4 h. Existence of moisture in the filler inclined to cause defects such as voids, pinholes and so on, in themanufactured composites. The optimal content of coupling agent (TiO 2 ) is 2 wt % of thefiller. The systems with 2 wt % of TiO 2  showed positive results. 5 Table 1.  Formation of PP/nano  a -Al 2 O 3  compositesNano  a -Al 2 O 3  content (Wt %) PP content (wt%) TiO 2  content (wt%)0 100 01 98.98 0.022 97.96 0.043 96.94 0.064 95.92 0.085 94.9 0.1 PP: polypropylene. Mirjalili et al.  455  at Universiti Putra Malaysia on May 17, 2012 jtc.sagepub.comDownloaded from   Compounding and processing  The melt blending of PP and nano  a -Al 2 O 3  powder was carried out using Thermo HaakePoly Drive with RheomixR600/610 blending machine at 175  C, with rotor speed of 50 rotations per minute (rpm) with a total evacuated chamber capacity of 40 g. The firststep of mixing involved the PP preheating for about 4 min. After preheating, the speed was maintained at 50 rpm for another 8 min to ensure uniform heat distributionthroughout the batch. Then, nano alumina filler was included and 2 min later TiO 2  powder was added. The rotor was stopped at the 12th min and the melted compound wastaken out for sheeting. The melt compound of PP/nano  a -Al 2 O 3  of the size 15  15 cmwere then formed by Hsinchu hot press machine. The compound was preheated for 2.5 min and hot pressed for another 3 min, under the pressure of 150 kg/cm 2 at 180  C,with 10 times of compression bumping. The sheet obtained was directly cooled with thecold press for 2.5 min of cooling cycle. Thermogravimetric analysis TheTGAanalysiswasperformedbyusingPerkinElmerTGA/SDTA7Model(Champaign,IL61822).Theweightofthesampleusedwasabout10mg.Thesampleswereheatedfrom35  C to 600  C at a heating rate of 10  C/min in a dynamic inert nitrogen atmosphere. Different scanning calorimetry analysis The different scanning calorimetry analysis (DSC) was performed using the Mettler Toledo TA Instruments DSC 823 Model (Swindon, SN2 1EU). The weight of sampleused was about 5–6 mg. The samples were encapsulated in aluminum pans and wereheated from 35  C to 250  C at a heating rate of 10  C/min in a dynamic nitrogen atmo-sphere with a flow rate of 10 ml/min. Each sample was held for 1 min at 35  C toeliminate the trapped moisture content. Dynamic mechanical analysis ThedynamicmechanicalpropertiesweremeasuredbydynamicmechanicalanalyzermodelPerkinElmerTE.Thesamplesfromcompressionmoldedplaqueswerecutintorectangular shapewiththedimensionof  * 60mminlength; * 13mminwidthand  * 3mminthickness.Themeasurementwascarriedoutusingthreepointsbendingflexuraltest.Thesamplesweresubjected to an oscillating frequency of 1 Hz and oscillating amplitude of 10  m m in thetemperature ranges of   30–80  C at a heating rate of 2  C/min. Results and discussion Thermal properties It is essential to understand the thermal tolerance of polymer composites because of thevariety of working environments of this composite in several engineering requests. Themajority criterion for plastic material employed in the requests like electronic packaging, 456  Journal of Thermoplastic Composite Materials 25(4)  at Universiti Putra Malaysia on May 17, 2012 jtc.sagepub.comDownloaded from 
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