Chapter Ii

Literature Review

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction A new class of materials based on organic and inorganic species combined at nanoscale level has gained ever more attention during the last decade. These new materials called nanoscale materials ordered nanocomposite; organic or inorganic hybrids can be considered as the composite in which at least one phase is of below 100-nm size. The polymer –clay nanocomposites first reported in the literature by Blumstin et al [1], author illustrated system with polymerization of vinyl monomers intercalated into montmorillonite. Nanocomposites are commonly based on the polymer matrices reinforced by modified nanofillers such as precipitated silica, silica alumina, silica beads, cellulose whiskers, zeolites, natural and synthetic modified silicates (Insitu method)[2-4]. Clays are intensively used in nanocomposites. The layered silicates (natural clay) like mica, laponite, fluorohectorite can be synthesized. Most of the recent studies have focused on the use of natural clay from smectite family “Montmorilonite” because of its layer charge density [5-7]. It is most widely used nanofiller. Montmorillonite contains in the addition varying amount of crystobalite, zeolites, quartz, felspar, Al2O3 identically found suitable in high cutting tools, high surface area support catalyst, tribological materials, heat sinks and magnetic recording heads [8].

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2.2 Synthetic Routes for Nanoparticles and Nano Composites 2.2.1 Synthesis of inorganic nano particles There are number of techniques currently available for the synthesis of nanoparticles of oxides and non oxides, these include laser ablation[9], microwave plasma synthesis[10], precipitation from solution[11], spray pyrolysis[12] and hydrodynamic cavitation[13], All these techniques are based on the particle size, distribution morphology, purity and degree of agglomeration .Spray pyrolysis produces the particle size near to 10 nm. Narrow size distribution is not possible in majority of technique. Nanoparticles less than 10 nm can possible to be synthesized by precipitation in liquid medium but particles can agglomerate. Chemical vapor condensation gives particle size 3-50 nm and its continuous scale up is possible. The PTFE nanoemulsion can advantageously be utilized as filler to create high performance materials assuring better homogenity, higher contact surface, better rheological characteristics. Kapeliouchko et al [14] have synthesized the nanoparticles with the help of microemulsion process. One of the principal problem in using PTFE as filler is difficulty of adhesion with other materials. He also developed the microemulsion polymerization together with various “core shell” techniques which permits to obtain materials for the optimal use as high performance filler. The microwave plasma process is capable of producing nanoparticulate powders with mean particle size in the range from 5 to 20 nm .The products may be oxides, nitrides, sulfides, selenides or even materials. Additionally, it is possible to coat these particles

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Literature Review

with a layer of second ceramic or a polymer. The resulting material is found to be the super magnetic [15]. Skandan et al [16] described a method for the production of oxides nanopowder by controlled thermochemical decomposition of metal organic precursor/carrier gas mixtures in the low pressure flames, specially designed burner is used to achieve a flat flame. Metal organic precursors introduced along with the fuel /air mixture experience complete and uniform decomposition, thereby yielding a uniform synthesis of SiO2, TiO2 and Al2O3 nanophases. The product of ball milling of the magnetic and amorphous silica (40-mole % Fe3O4) for an extended period of time in closed vessel has been investigated by Koch et al [17]. It is found that the milling induces an extensive reduction of Fe(III). The material constitutes a mixture of

ultrafine Fe rich spinel particles

(magnetite/maghemite).Nanostructure oxides prepared, chemically have hydroxides as intermediate precursor phases, therefore nanocrystalline oxides such as zirconia, titania and magnesia system are prepared with sol gel technique. The temperature evolution of hydrolyzed zirconium, titanium, and magnesium until they form the corresponding nanocystalline oxides [18]. Al2O3 ceramics are important structure ceramics but α-Al 2O3 is stable phase after calcination at high temperature, which easily promotes the growth of grain powder and makes it difficult to get in nanoform, and other reason is Al 2O3 particles get agglomerated during dehydration process. Considering the problem Wang et al have prepared nanoscale α-Al2O3 powder with polyacrylamide gel method as shown in figure1. Because polymer-network inhibits the aggregation of Al 2O3 due to which nanoscale α-Al2O3 powder with of size 10 nm can be obtained. Its calcination

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Literature Review

temperature is 11000C, which is 100 0C lesser than general calcinations temperature use for other methods.

Fig 2.1: Nanosynthesis of Al2O3 by sol gel technique [8] The microemulsion approach is a promising method to prepare nanometer size particles. Microemulsion process technique can be employed for variety of the chemicals such as Ag, ZrO2 and Ba, TiO2 etc., the nanometer sized titania particles have been prepared by chemical reaction between TiCl4 solution and ammonia in the reversed microemulsion system[19]. Nano-TiO2 whiskers were prepared through controlled hydrolysis of titanium butoxide. The nano-TiO2 whiskers obtained were anatase and grew selectively in the (001) direction with a diameter of about 4 nm and length of about 40 nm. Acetic acid played an important role in the oriented growth of nano-TiO 2 whiskers [20]. New development in the synthesis of nanometer scale TiO2 particles have enabled the processing of existing new nanoparticles / epoxy composites. An

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Literature Review

ultrasonic method was used to disperse the nanoparticles in epoxy, thus this method eliminates the need of solvent without sacrificing the ease of processing [21]. It is interesting to know that the transformation behavior from amorphous to anatase or rutile phase is influenced by the synthesis condition. Most of the literatures show that alkoxides based sol-gel or precipitation process yield amorphous titania precursors or powders or powders with the anatase phase. [22-24 ]. At present there are few studies on the preparation of nanodispersed titania powder from TiCl 4 or Ti(SO4)2. Akhatar et al [25-26] have investigated gas phase synthesis of Titania by TiCl4 oxidation in presence of dopants. Ocana et. al.[27] obtained rutile TiO2 powder at 98 oC, using 3M TiCl4, for measuring it’s IR and Raman spectra, but did not comment on fabrication method production. Terwilleger et. al.[28] prepared the rutile phase TiO2 powder with an average grain size < 20 nm by doping with small amount of Sn, which is the mixture of SnO2 and TiO2 . Manufacturing of TiO2 is possible with simplified and low cost continuous process, in addition the Titania powder of anatase phase was prepared without calcination, with particle size 4 nm reported by Zhang et. al. [29]. Nano structure materials with well defined size are generally used in the catalyst and the chromatographic separation processes. Brinker et al [30] described the production method for silica with the help of rapid aerosol process. The evaporation of solvent during aerosol generation induces multiphase assembly confined to an aerosol droplet containing polystyrene spears silica, polystyrene spears /surfactant/silica or microemulsion silica. After removal of surfactants, polymer spears, and microemulsion the resulting material exhibits controlled meso-and macro-porosity [31]. Various routes used for production of the Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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Literature Review

nano particles found some considerable disadvantages such as difficulty in handling and processing of the nanoparticles. Number of workers [32-40] investigated novel matrices for mediated control of CaCO3, K2CO3, CdS, CaSO4 Ca3(PO4)2, Mg(OH)2 which are synthesized using matrix mediated growth technique like polyethylene oxide, polyethylene glycol, polyvinyl acetate. Radhakrishan et al [41] reported that an increase in ratio of polymer (PEG or PEO) gives considerable reduction in the nanosize compared to the commercial available nanoparticles. Nanostructure materials of perovsketite type oxides, LaMnO3, and LaCO3, have been prepared by Min Chen et al [42]. They have used three different methods such as sol gel, precipitation and amorphous complexometry observed the effect of the synthesis methods on structure and catalytic activity, and tried to optimize the catalytic activity of CO oxidation of LaMnO3. A chemical Precipitation method has been implemented by Muhammed et al [43] for synthesis of ZnO nanoparticles with controlled morphology. Several precipitation reagents are used. Ammonium carbonate has also been used as precipitating reagent which leads to unusual rod shape morphology, flow injection technique has been developed to synthesize nanophase particles of zinc oxide. The average particle size of ZnO obtained using the injection flow technique was of approximately 20 nm, while the crystal size as measured by the X ray pattern was of 10-15 nm. Ultrafine, equiaxed and monodipserse oxide particles with the average grain diameter in the range of 1-10 nm have been prepared by Colinet et al [44] by two step chemical approach; the chemical reduction of metallic salts obtained by activated sodium hybrids in tetrahydronfuran solvent followed by oxidation of the metallic species with small Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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Literature Review

amounts of O2-N2 gas. Such particles are easily, quantitatively and reproducibly, prepared and are stable on the storage.

2.3 Preparation Methods of Mineral Clays and Polymer Nanocomposites Polymer –clay interactions have been actively studied during sixties and the early seventies. An oraganophilic clay showed dramatic improvements of mechanical, barrier properties and the thermal resistance as compared with pristine matrix and at low clay content (4 wt %). Since then the polymer –clay composites have been divided in the three general types; i) Conventional composite where the clay acts as a conventional filler, ii) Intercalated nanocomposite consists of regular insertion of the polymer in between the clay layer and iii) Delaminated nanocomposites where 1nm thick layers are dispersed in the matrix forming a monolithic structure on the microscale. Clay contains the negatively charged layered silicates bound with metal cations such as Na+ or Ca++. The clays are initially modified and then used. Modifications are done with the help of surfactants, swelling agents to improve the surface properties of the polymers. Number of authors have studied the systems of the polymer –clays such as clay polyimide [45], clay-PP, [46-49],Na+ MMT clay Poly(vinyl alcohol) [50], smectic clay poly(methyl methacrylate)[51],silicate-polyethylene oxide [52-53],clay-nylon[54-56],clay-epoxy[52], clay-polyurethane[58], Clay-PS[59-60],polyaniline [61], clay-polybenzoxazole [62]. Manias et al [46] reviewed the PP/montmorillonite nanocomposites. The nano composites are achieved

in two ways either by using the functionalised PP and

common MMT clay or by using neat /unmodified PP and a semi fluorinated organic modification for silicates. All the hybrids can be formed with solventless melt Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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intercalation or extrusion. Small addition less than 6 % of the nanoscale inorganic filler improves the properties such as the tensile characteristics high barrier properties better scratch resistance and increasing flame retardancy. Zr, Ti and Ti-Zr mixed oxides pillared montmorillonite (PILC) has been prepared by Das et al [61]. MNT was used as a starting material and before pillaring, it was subjected to exchange with Na+ ions, finally the additions of the respective samples were treated with chlorides. They have used the prorled MNT-Ti samples for the nitration reactions as the solid catalyst are generously employed. it was subjected to exchange with Na+ ions, finally the additions of the respective samples were treated with chlorides. They have used the prorled MNT-Ti samples for the nitration reactions as the solid catalysts are generously employed.

2.3.1 Intercalation and exfoliation mechanism of polymer nanocomposites

Fig 2.2: Intercalation of polymer chains in nanoparticles layer Two terms (Intercalation and exfoliation) are use generally used to describe the two classes of nanocomposites that can be prepared. Intercalated structures are self Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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assembled, well ordered multi layered structure where in the extended polymer chains are inserted in to the gallery spacing between parallel individual silicate layers separated from 2 nm to 3 nm (Fig 2). The delaminated structure result when the individual silicate layers are no longer close enough to interact with the adjecent layers. In the delaminated cases the interlayer spacing can be of the order of the radius of gyration of the polymer, therefore the silicate layers may be considered well dispersed in the organic polymers. The silicate layers in a delaminated strucutre may not be well ordered as in an intercalated structure. Both of these hybrid structures can also coexist in intercalated in the polymer matrix; this mixed morphology is very common for composites based on smectite silicates and clay minerals. X-ray diffraction measurements can be used to characterize these nanostructures. Diffraction peaks in the low angle region indicate the d spacing (basal spacing) of ordered intercalated and ordered delaminated nanocomposites ; disordered nanocomposites shows no peaks in this region due to the loss of structural registry of the layers and the large d spacing (> 100 nm)

2.4 Mechanical, Thermal, Physical and Rheological Properties of -Nanocomposites The presence of a compatibilizer such as the Maleic anhydride grafted PP is important for obtaining the improvements in the nanocomposites of clay. The important characteristic is that the presence of the polar group of MAH-g-PP affects dispersion of the clay layers in the composite and that is why it enhances the properties. Jog et al [62] have studied the dynamic mechanical behavior, crystallization and morphological behavior of PP-clay system. And found that the PP/clay system exhibits a disordered Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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structure from by XRD patterns. The thermal degradation temperature increases from 270 to about 330 0C. DMA shows the significant improvements in the storage modulus. The intensity of the loss modulus peak is reduced, showing weak cooperative relaxation of PP in the PP/clay composites. Polymeric nanocomposites based on the exfoliated organophilic layers of silicates and polymer-mineral nanofillers exhibit the unique property profiles such as the elevated heat distortion temperature combined with improved stiffness, strength, impact resistance of elastomers, improved thermal stability, lower thermal expansion coefficient, barrier against permeation of the gas and liquids rheological control and less abrasion during the processing, reduced flammability [63]. Theoretical study of the tensile strength of the polymer-filler composites is important aspect, Chow et al [64] have developed the predictive model which shows that the tensile strength of a particulate-filled polymers which depends not only on the volume fraction of the fillers and elastic moduli of two phases but also on the shape, size and the interfacial adhesion of the filler particles and the matrix. Polymer –graphite composites are of increasing attention due to their important electrical properties. The need of the electrical and thermal conductivity of polymer composites is in the electrical circuit boards and heat exchangers, Kripa et al [65] have investigated thermal diffusivity and electrical conductivity of PP-graphite and HDPEgraphite system (semicrystalline matrix), investigators used the graphite systems with different particle sizes and specific surface area. Intercalated version offers the reduced flammability benefits, but with less improvement in the physical properties, this issue is still unidentified. Gilman et al [66] focused on mechanism of the flammability reduction Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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with

recent

results

for

PP-graft-Malic

anhydride

and

PS-layered

silicates

nanocomposites using the MMT and fluorohectorite. Intercalated nanocomposites of modified montmorillonite clay in glassy epoxy were prepared and studied by Zedra et al [57].

Aliphatic diamine used as crosslinking agent. These materials found an

improvement in Young’s modulus but the corresponding reduction in ultimate strength and strain to failure; the fracture behavior appears to be most dramatically improved in the intercalated systems. The fracture energy increment was reported by 100% with clay concentration of 5 wt %. The effect of Nylon–6 molecular wt on the mechanical and rheological properties of the nanocomposites formed from organically modified layered silicates by melt processing has been extensively studied by the Paul et al [54]. Tensile modulus and yield strength were found to increase with increasing concentration of clay while the elongation at break was found to be decreasing; Izode impact strength was found to be independent of the increase of the clay content for lower molecular wt. polyamides. Capillary and dynamic parallel plate data revealed sizeable difference in the level of shear between each nanocomposite system, mechanism for exfoliation during the melt mixing is outlined. Organically modified silicates improve the barrier properties by exfoliation or intercalation so alkyl–ammonium modified Montmorillonite, a biocompatible layered silicate frequently used in cosmetics and food supplements. Runt et al [61] Synthesized Polyurethane urea (PUU) with condensation reaction, and found a considerable reduction in water vapors and oxygen permeability in PUU-PIB comb polymers. They have invented significant reduction in the gas permeability with simultaneous improvement in the mechanical properties, they have also achieved Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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concurrent property enhancement that could not be achieved with chemical modification of polyurethane polymers. The average mechanical properties for PUU/PUU layered nanocomposites are summarized in Table 2.1. Composites (Wt% Modified Silicate) Neat PUU

Modulus E50 (MPa)

Tensile Strength (MPa)

3.38± 0.21

27.4 ± 2.9

800± 50

1 Wt % 3 Wt % 7 Wt % 13 Wt %

3.93± 0.34 4.34± 0.48 4.96± 0.34 8.83± 0.48

31.4 ± 2.3 31.4± 3.2 32.1± 1.4 34.8± 1.9

890± 50 950± 40 1040± 60 150± 50

20 Wt %

11.51± 0.55

37.4± 1.7

1230± 70

Table 2.1: Mechanical nanocomposites

Properties

of

PUU

and

Elongation to break(%)

PUU/

Layered

Silicate

The nanodispersed silicates result in a significant increase in modulus, strength and stiffness e.g. for the 20-wt % composite, by more than 300% and 30% respectively. However, incontrast to conventional filled polymer systems, the increase in stiffness and strength does not come at expenses of the ductility. A silica (Aeorsila200V) has been functionalised by reaction with methacryl propyl trimethoxy silane (MPTMS)in toluene by Guyot et al[62]. It has been found that functionalised silica gives very high elongation at break. Liu et al [67] prepared composites by grafting -melt compounding using a new kind of co-intercalation organophilic clay which had larger interlayer spacing than ordinarily modified alkali ammonium clay. One of co-intercalation monomers was unsaturated so gives grafting reaction. Incorporation of silicate layers gives improvement in the storage modulus and decrease of Tan δ value. Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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Mechanical properties and crystallization behavior of the syndiotactic PP as function of the silicate content has been studied by Mulhaupt et al [49]. Melt compounding of s-PP with organohectorite, obtained via cation exchange of fluorohectorite with octadecylammonium cation, it has been found that the Young’s modulus has been increased five times with increasing content of the organophilic silicate nanoparticles, the yield stress was increased in considerable value in the s-pp. Styrene–clay nanocomposites were prepared by free radical polymerization of styrene containing dispersed organophilic MMT, Fu et al [60] achieved the higher dynamic modulus and higher decomposition temperature than pure polystyrene. Due to formation of the aggregation of the nanoparticles and shear heating the melt mixing of nanoparticles with high performance of the polymers is not possible. Jana et al [68] investigated the feasible alternative solution to this problem, they used the lower molecular weight polymer (epoxy) as reactive solvent and dispersing agent. They found that there was considerable improvement in viscosity and processing temperature of polyethersulphone (PES); there were considerable improvements in the barrier resistance and heat deflection temperature over heats neat PES. Nano TiO2-epoxy system has been developed by the Schelder et al [69], an ultrasonic method has been used to disperse nanoparticles in epoxy composites. Composites were processed at different loading, and exfoliated the exceptional strain to failure and scratch resistance of the system. The γ-Fe2O3 nano particles coated with DBS and CTAB were prepared by Liu et al [70] by microemulsion process, the coated samples with surfactant showed the

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considerable enhancement in the nonlinear optical properties compared with their bulk counter part. The geometry and the orientation of the filler particles have significant influence on the thermal conductivity of the composite material. Many of the theoretical treatments are valid for only specific types of the filler particles and composite constructions, Bigg et al [71] includes the theoretical calculations and the models predicted for the calculation of the thermal conductivity of the spherical and the irregular shape fillers, long fibers and flakes. Thermal conductivity and particle effect are not yet theoretically predicted. The optical transparency of the PP-nanoparticulate composite with calcium phosphate has been studied by Radhakrishanan et al [41], optical transparency of the PP/nanoparticle composite was found much higher than the conventional calcium phosphate samples.The vapor permeation of the silica nanoparticles was studied by Dufaud et al [77]. This study characterizes the influence of the novel silica particles in acrylate matrices on transport phenomena, the vapor permeation experiments confirm the decrease in transport properties with the loading. The Photovoltalic properties of nanostructure ZnO (Wurtzite) electrodes have been investigated by Keis et al [73], photochemical studies were carried out on various types of electrodes with controlled morphology of particle size and doping. The monochromatic photon to current was recorded in the UV spectral region on bare ZnO and in the visible region on the ruthenium dye sensitized cells. The results showed relatively high efficiencies for such systems and demonstrated the potential of ZnO nanostructure cells as materials for photovoltaic applications.

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Polymethyl methacylate filled silica particles of nanometric size were synthesized by Hajji et al [74] using a five step procedure. Different types of materials were prepared by changing the particle size (50 to 80 nm in diameter) and the weight fraction of silica (in the range of 5-30 wt. %). Study of their swelling in chloroform showed that tridimensional structure were likely to be formed, especially at high silica wt. fraction and small particle size. As far as the thermo-mechanical properties are concerned, the main relaxation temperature, Tα , was shown to be unaffected by changes in sample formation, as expected the glassy modulus increased with the wt.fraction of silica, in quite good agreement with the predictions of theoretical models. Finally the yield stress behaviour was found to be related to a peculiar organization of the methylmethacylate chains in the systems. Model composites, consisting of an amorphous matrix (PMMA) filled with the simple shaped nano particles of silica have been elaborated by Reynaud et al [75]. Three different ways an industrial route, a solvent technique with use of acetone and mechanical alloying, and evolution of the dynamical mechanical thermal properties are discussed with regard to the filler content. Eventually the comparison is drawn from 10 wt % filled systems, enlightening the elaboration influences on the microstructure. Calypolyimide(3,3’,4,4’-benzophenone tetracarboxylic dianhydride-4,4’-oxydianiline (BDTAODA) nanocomposites were synthesized by Wai et al [45]. These nanocomposites were synthesized from ODA modified MMT and poly(amic acid). Organoclay/BDTA –ODA nanocomposites were synthesized via ODA-modified organoclay display large increase in modulus and in maximum stress are observed as compared to pure BDTA-ODA. A two-fold increase in modulus and a half fold increase in maximum stress in case of 7:93 Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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ratio of organoclay /BTDA-ODA. In addition the elongation at break of the organoclay /BTDA-ODA nanocomposites is even slightly higher than the pure BTDA-ODA which is in sharp contrast to that of conventional inorganic-filled polymer composites.

2.5 Flammability and Thermal Stability Blumstein et al [1] reported the improved thermal stability of polymer clay nanocomposites that combined Polymethylmethacylate (PMMA) and Montmorillonite clay. A Clay–rich nanocomposite not only exhibits mechanical properties but also enhances polymer thermal properties. The Cone-Calorimeter is one of the most effective bench-scale method for studying the flammability properties of material. The cone calorimeter measures fire relevant properties such as heat release rate (HRR), and carbon monoxide yield, among others. Heat release rate, in particular peak HRR has been found to be the most important parameter to evaluate the safety. Gilman et al [66] have characterized the flammability properties of a variety of polymer-clay nanocomposites, under the fire like condition, using the cone calorimeter. The calorimeter data shows that both the peaks and average

HRR

were

reduced

significantly

for

intercalated

and

delaminated

nanocomposites with low silicate mass fraction (2% to 5%). (Table 2) Sample (structure)

Nylon-66 Nylon-66 silicate nanocomposit

Resi dual Yield (%) ± 0.5 1 3

Peak HRR (∆%) kW/m2

Mean HRR (∆%) kW/m2

Mean Hc (MJ/ kg)

Mean SEA (M2/Kg)

Mean CO yield (Kg/Kg)

1,010 686

603 390

27 27

197 271

0.01 0.01

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e 2% Delaminated Nylon –66 silicate – nanocomposit e5% delaminated

6

378

304

27

2 96

0.02

PS PS Silicate – mix 3% immisicible

0 3

1,120 1,080

703 715

29 29

1,460 1,840

0.09 0.09

PS silicate – nanocomposit e3% Intercalated /delaminated PS W/DBDPO /Sb2O3, 30% PP PP silicate nanocomposit e 2% Intercalated

4

567

444

27

1,730

0.08

3

491

318

11

2,580

0.14

0 5

1,525 450

536 322

39 44

704 1028

0.02 0.02

Table 2.2: Data sheet of thermal properties of different polymer Nanocomposites

2.6 Structural Characterization of Nanoparticles and Nanocomposites 2.6.1 Crystallization behavior study Process history and use of temperature determine the relative fraction of the crystalline polymer phases in the semicrystalline polymer composites, and thus have significant influence on the stability of the crystalline region at the elevated temeperature. Vaia et al [56] studied the influence of nanodisperesed MNT layer and process history on the crystal structure of the nylon-6 between the room temperature and it’s melting. XRD and Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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TEM have been taken in account to note the behavior. The temperature dependence of total crystallinity and relative fraction of α - and γ -phases imply that the γ -phase is preferentially in the proximity of the silicate layers whereas the α - phase exists away from the polymer silicate interface region.Liu et al [48] studied the nonisothermal crystallization behavior of polyamide –6/ clay nanocomposite (PA6CN) with the help of differential scanning calorimeter (DSC) and X-ray diffraction (XRD). DSC results showed that the nanometric silicate layer in the PA CN acted as an effective nucleating agent. The addition of the silicate layers influenced the mechanism of nucleation and the growth of Polyamide. It has been found that the addition of the silicate layers favored formation of the γ crystalline form, the crystallinity degree of PA CN increased with increasing cooling rate. Authors have also proposed a Non-isothermal kinetic model. The crystallization behavior of the syndiotactic PS-clay nanocomposite has been investigated by Chang et al [76] The crystallization behavior of α -and β -crystals for syndiotyactic PS nanocomposites has been investigated by the DSC and FTIR. The results show that the presence of the clay plays important role in facilitating the formation of the thermodynamically favorable β form crystal when the s-PS is melt or cold-crystallized.

2.7 Dynamic Heterogeneity Numbers of the nanoscale system experiments have been done for the studies of dynamical properties of the confined chains [77-81]. Fluids in nanoscopic confinement posses a variety of unusual properties and in particular, remarkable dynamic Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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hetrogenities, which varies on the length scale as short as a function of nanometer. Zax et al [82] applied their efforts on the use of the nuclear magnetic resonance spectroscopy to nanoscopically confined polystyrene (PS) created by the intercalation into surface modified fluorohectorite. A comparison of surface-sensitive cross polarization experiments with spin-echo experiments was also done; it has been suggested that the PS in the center of nanopores is more mobile than the bulk at comparable temperatures, while the chain segments which interact with the surface are dynamically inhibited. Molecular modeling and rotational-isomeric-state model have been used for initial confirmation of PS.

2.8 Surface Characterization Polymer surfaces play an important role in their application such as adhesion, protective coating, friction and wear, microelectronics and thin film technology. However up till now the term surface has not been well defined because a surface defined by one technique can be the bulk as revealed by another technique. Chan et al [83] used the time flight secondary ion mass spectroscopy (TOF-SIMS), X-ray photoelectron spectroscopy(XPS) and tapping mode atomic force microscopy(TM-AFM) to study surface of the poly(N-vinyl-2 pyrrolidone) thin films containing nanoparticles. The study XPS suggested that the concentration of the silica particles increases as the sampling depth increases. TM-AFM phase imaging is shown to be capable of detecting the presence of these sub-surface nano particles. Polymer dispersed liquid crystals (PDLC) are important in development of electronic appliances. Bunning et al [84] have used the small-angle X ray scattering and high resolution scanning electron microscopy for Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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detecting the nano and mesoscale morphology of the polymer dispersed liquid crystal films(PDLC) of varying the liquid crystal (LC) concentration.

2.9 Dispersion of Clay It is well known that the dispersion of clay affects mechanical and thermal characteristics of the nanocomposites, means degree of the dispersion of clay decides the properties of nanocomposites. Small-angle neutron scattering (SANS) is excellent tool to prove the degree of separation or dispersion exchanged clay mineral in a solvent. Hanley et al [85] has used SANS to investigate the dispersion in toluene of various forms of the cloisite C-15A complex.

2.10 Rheological Behaviors of Polymer Nanocomposites The rheological properties of insitu polymerized nanocomposites with end –tethered polymer chains were first described by Zax et al [82]. Recently polymer/clay nanocomposites with polyaniline and styrene/acrylonitrile copolymer have been introduced as candidate materials for drybas electro-rheological (ER) fluids. In ER application, there rheological properties of dispersed clay polarizable colloidal suspension under external electric field strength change abruptly via structural change in the particle aggregation in either chain or column like structures. Kim et al [51] studied the strongly hydrophobic PS was intercalated into the hydrophilic silicate layers via emulsion

polymerization which has been previously sued to produce

nanocomposites consisting of poly( metyl methacrlate), polyaniline or syrene

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/acrylonitrile copolymer and Na+- MMT are filled with sodium cations , the hydrophilic properties are enhanced and lead to a high degree of swelling in water.

2.11 Polyamide 66 Clay Nanocomposites Polymer/organoclay nanocomposites present unique properties that are not observed in conventional composites. Incorporation of small amounts of organoclay (<10wt.%) into polymer matrices may remarkably improve dimension stability, mechanical, thermal, optical, electrical, and gas barrier properties, and decrease the flammability. This happens due to the large contact area between polymer and clay on a nanoscale as reported on literature [1–11]. The incorporation of organoclays into polymer matrices has been known for 50 years and one of the pioneering works was from Toyota as reported by Cho and Paul [87]. To be compatible with polymer matrices, sodium smectite clays need to be modified by using quaternary ammonium salts with at least 12 carbon atoms in aqueous dispersions. In these dispersions, the clay particles or layers must be separated one from another and not be stacked in order to facilitate the introduction of the organic compounds. As a result, the clay exchangeable cations are replaced by the organic cations of the quaternary ammonium salt that are adsorbed on the negative sites of the clay surfaces. The obtained clay is known as organoclay [7– 12]. Polyamide 66 (PA66) is an important engineering plastic, but PA66 matrix nanocomposites have been little investigated by researchers up to now [13–15]. The Na-MMT clay can be modified organically (named as organoclay) with quaternary ammonium salt according to the procedure [16].

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2.12 Structure of PA66/Clay Nanocomposites. Figure 3 presents the X-ray diffraction patterns for the PA 6,6 systems with 2 wt.% of unmodified (MMT) and modified clay (OMMT). The interlayer distance was determined by the diffraction peak in the X-ray method

using the Bragg equation. It can be

observed for the modified clay (OMMT) three peaks corresponding to an interlayer spacing d001 of 29.2, 19.2, and 12.5 A° . The two first peaks indicate that the intercalation of the salt between the layers of clay has occurred. According to the literature [91, 92] another peak corresponds to interlayer spacing’s of 12.5A° (d001 for unmodified clay-MMT) is probably due to an incomplete ion exchange, with some residual Na-MMT remaining in the material. . The results indicated that the quaternary ammonium salt was intercalated between two basal planes of OMMT leading to an expansion of the interlayer spacing. It can be observed for PA6,6/MMT system a diffraction peak around 14.71 A° , which is close to the distance of 12.5 °A of the unmodified clay indicating that the increase of the basal spacing practically did not occur. On the other hand, the sample of the nanocomposites of PA6,6 with the modified clay (OMMT) presented the displacement of the XRD peak toward a lower angle values, which represents an increase to 19.20 °A in the basal spacing. It can be thus noticed that with the organoclay presence, the peak related to the PA66/unmodified clay interlayer spacing disappeared and a new broad diffraction peak appeared. This peak may be due to the intercalation/partially exfoliation of the polymer chains between the layers of organoclay. These results were be confirmed by TEM. Figure 4 shows the TEM images of the PA66 system. In Figure 3(a), it can be seen clearly agglomerates of Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

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clay and in Figure 3(b) exists intercalated clay layers but it can be seen too several exfoliated clay layers present in the PA6,6 matrix. Therefore, the obtained PA66/OMMT systems are partially exfoliated nanocomposites according to the XRD pattern (Figure 4) and the literature [86-92 and 98-100].

Figure 2.3: XRD patterns of montmorillonite clay modified with Praepagen salt (OMMT),A66/MMT, and PA66/OMMT nanocomposites. [101]

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Figure 2.4: TEM photomicrographs of (a) PA66/MMT and (b) PA66/OMMT Nanocomposite.[101]

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REFERENCES 1. A.Blumstein, Bull.Chim.Soc.,899, 1961 2. Usuki,A.,Kojima,Y.kawasumi,

M., Kamigaito,O.,J.Mater.Res., 8:1179,1993

Okada,A.,Fukushima,Y.,Kurauchi,T.and

3. Lan,T.,Pinnavaia,T.J.,Chem.Mater., 6:2216,1994 4. Usuki,A.,Kato,M.,Okada,A.,and Kurauchi,T.,J.App.Poly.Sci. 63:137,1997 5. Kato,M.;Usiki,A.;Okada,A J.Appl.Polym. Sci, ,66:1781-1785,1997 6. Kawasumi,M;Hasegawa N,M.Usuki,A;Okada,A,Macromolecules30:6333-6338,1997 7. Hasegawa,N; Kawasumi,M; Kato,M.; Usuki,AOkada,A,J.Appl.Polym.Sci 67:87,1998 8. H.Wang, L.Gao, W.Li, Q.Li Nanostructure materials 11,(8):1263, 1999. 9. G.F.Gaertner and H.Lydtin, Nanostruct.Mater., 4559,1994 10. D.Vollath,in 2 nd International business Conference on nanostructure Materials and

Coatings ,org by Gorham-Intertech1995 11. D.Gallaghar,W.Heady,J.Racy,andR.Bhragava,J.mater.Res 10:870 ,1994 12. G.Messing ,S.Zang,and V.Jayanthi,J.Am.Ceram.Soc. 76:2707 ,1993

Mosser, B. Geurts and J.Sunstrom IV,in Proceedings of 1st International Confenrence on Naoparticulates,Org.by Gorham-Intertech 1994

13. William

14. V.Kapeliouchko International Symposium Eorofillers France, 18:62,1999, 15. D.Vollath,D.V.Szabo,J.Fuchs, NanostructureMeterials, 12:433, 1999 16. G.Skandan, Y-J.Chen, N.Glumac and B.H.Kear Nanostructure materials 1, 2, 158,

1999, 17. B.C.Koch,Jiang and S.Morup Nanostructure materials 2:233, 1999 18. X.Bokhimi, A.Morales, M.Portilla and A.Garcia-RuizNanostructure materials 12:589,

1999 Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

45

Literature Review

19. G.L.Li and G.H. Wang Nanostruct. Mat. 11, (5):663, 1999 20. Y.C.Zhu, C.X.Ding Nanostructure Materials 11:(3),1999. 21. C.B.Ng,L.S.Schadler andR.W.Siegel Nanostructure materials. 12:507,1999. 22. J.Y.Chen,L Gao,and J.H.Huang,J.Mater.Sci, 31:3497,1996 23. D.C.Hague and M.J.Mayo,J.Am.Ceram.Soc. 77,1957,1994 24. K-N.P.Kumar,K.Keizer,A.,et al. Nature 358:48,1992 25. M .Aakhatar S.E.Pratsinis J.am Ceram.Soc 75:3408,1992 26. M.K.Akhatar ,S.Vemury and S.E.Pratsinis Nanostructrure mater, 4:53, 1997 27. M.Ocana V.Fornes, J.V.G.Ramosand C.J.Serna, J.Solid State Chem, 75:364,1988 28. C.D. Terwilliger and Y.M. Chiang nanostructure Mater. 2:37,1993 29. Zhang Q.H.,L.Gao,J.KGuo. nanostructure materials, 11(8):1293,1999 30. C.J.Brinker, F.Hongyou, F.V.Swol, L.Yunfeng, Journal of non-crystalline solids

285:71,2001 31. Dagani R.C and E News 77(23):25,1999 32. Yu.D ,Godovski, Adv Polym sci 119:79,1999 33. Sherman L. M., Plastic Technol. 45(6):53,1999 34. S.Radhkrishanan, C.Sujaya,. Polymer 42,6723. ,2001 35. Mishra S, Sonawane S. H, Singh R. P, Bendale A, Patil K, J. Appl. Polym. Sci.,

94:116 ,2004 36. Mishra S, Sonawane S H & Singh R P, Studies on characterization of nano CaCO3

prepared by in-situ deposition technique and its applications in PP-nano CaCO3 composites, J Polym Sci Part B: Polym Phys, 43 107, 2005 37. S Mishra* and N G Shimpi, Comparison of nano CaCO3 and with fly ash filled

styrene butadiene rubber on mechanical and thermal properties, Journal of Scientific & Industrial Research 41:744,2005

Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

46

Literature Review

38. Mishra, S.; Sonawane, S. H.; Singh, R. P.; Bendale, A.; Patil, K J Appl Polym Sci,

94:116,2004 39. Mishra S. and Shimpi N. G. Journal of Applied Polymer Science 98:2563, 2005 40. S. Mishra, N. G. Shimpi Journal of Applied Polymer Science, Vol. 104:2018–2026

2007 41. S.Radhkrishanan, C.Sujaya,. Polymer 42,6723. ,2001 42. M.Chen and X.M.Zheng Indian Journal of Chemistry 41A:2277, 2002. 43. M.Muhammad, L.wang J.Mater.Chem., 9:2871,1999 44. B.Colinet,.I.Cherrey,O.Tillement,J.M.Dubois,F.Massicot,Y.Fort,J.Ghanbaja,Material

Sci.and Engineering A338:70, 2002 45. K.H.Wai, H.L. Tyan, , T.E. Hsieh Journal of Polymer Sci., Part B, Polymer Physics,

38:2873, 2000 46. E.Manias,A.Touny,L.Wu,K.Strawhecker.B.Lu,

C.Chung,Chem.Mater. 13:3516,2001 47. S.Hambir, N.Bulakh, P.Kodkire, R.Kalgaonkar, J. P .Jog, J. Polymer Sci. PartB,

Polymer Physics 39:446-450 , 2001 48. X.Liu ,Q.Wu.,Polymer 42:10013 , 2001 49. R. Mulhaupt, D.Kaempfer, R.Thomann, , Polymer 43:2909,2002 50. E.Manias, K.E.Strawhecker , Chem Mater. 12:2943,2002 51. M.Okamoto,S.Morita.Y.H.Kim,T.Kotaka,H.Tateyama Polymer, 42:1201,2001 52. B.Liao, M.Song,Y.Pang Polymer 42:10007,2001 53. H.W.Chen, F.C.Chang, Polymer, 42:9763 ,2001 54. D.R.Paul, T.D Fornes, P.J.Yoon, H.Keskkula, Polymer 42:9929 , 2001 55. E.Reynaud ,T.Jouen,C.Gauthier,G.Vigier,J.Varlet, Poylmer, 8759 , 2001 56. R.A. Vaia, M. Lincoln, Z.G.Wang, B.S.Hsiao R.Krishnmoorti Polymer, 42:9975,

2001 Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

47

Literature Review

57. A.S. Zerda, A.J.Lesser,J.Polymer Sci.Part B:Polymer Physics, 39:1137,2001 58. R.Xu, E.Mainas, A.J. Snyder,J.Runt,Macromolecules, 34:337-339,2001 59. R.T. Chen-Rui, J.Y.Wu, H.Y.Lee, F.C. Chang ,Polymer 42:10063 , 2001 60. X.Fu, S. Qutubiddin, Polymer 42:807,2001 61. D.Das,H.K. Mishra, K.M.Parida and A.K. Dalai Indian Journal Of Chemistry,

14A:2238,2002 62. J.P.Jog

S.Hambir, N.Bulakh,P.Kodgire, R.Kalgaonkar, Science,,Part B, Polymer Physics , 39, 446, 2001

Journal

Of

Polymer

63. F.Dietrsche, C Dietrich, M.Ganter,P.Reichert, R.Mulhaupt Eurofiller Conference 99,

Lyon –Villeubanne, Sept 6-9 ,1999 64. T.S. Chow, J.C.Wilson Center for Technology ,Xerox Corporation ,Webster ,New

York Journal of Polymer Science : Polymer Physics Edition , 16:959-965,1978 65. I.Kripa , I. Chodak , European Polymer Journal, 37:2159 ,2001 66. J.Gilman,E.Manias,E.P.Giannlis,M.Wuthenow,New advances in the flame Retardant

Technology.Proceedings.Fire Retardant Chemicals Association.Oct2427,99,Tucson,AZ,Fire Retardant Chemicals Assoc.,Lancaster,Polyacrylamide, 22,1999, 67. X. Liu, Q. Wu European Polymer Journal 81:383 , 2002 68. C. Jana, S.Jain, Polymer 42:6897, 2001 69. L.S. Schadler, C.B.Ng.,R.W. SieGel Nanostructure Materials 12:507,1999 70. T.Liu,

L.Guo, Y.Tao, T.D. Hu, Y.N.Xie, J.Zhang, NanoStructure Materials 11,8:1329,1999

71. D.M. Bigg, Advances in Polymer sicinece 119:11995 72. O.Dufaud , E.Favre, C.Vu , Cm36, Euroffiller conference , 6-9.Sept 1999, 73. K.Keis,L.Vayassieres,S.A.Lindqueist,A.Hagfeldt,Nanostructure Materials, 12:487 ,

1999 74. P.Hajji,L.David, J.F. Gerard, J.P. Pascault,G.Vigier, Cm34, Eurofiller,99- Lyon –

Villeurbanne, September, 6-9, 1999 Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

48

Literature Review

75. E.Reynaud,C. Gaunthier,L.Ladouce,P.Perriat., Cm26,Euroffiller conference, 6-9,

1999 76. F.C.Chang C.R.Tseng, J.Y. Wu,H.Y.Lee, ,Polymer, 42:10036, 2001 77. A.M.Homola H.Nguygen and G.Hadzziioannou,J.Chem. Phys. 94:2346 , 1991 78. J.P.Montfort and G.Hadzziioannou, J.Chem. Phys 88:7187,1988 79. M.L.Gee P.M. McGuiggan, J.N.Israelchvili and A.M.Homola,J.Chem. Phys, 93:1895,

1990 80. J.Van Alsten and S.Granick, Macromolecules, 23, 4856 ,1990 81. H.Hu, G.A.Carson and S.Granick Physics Rev.Lett. 66,2758, 1991 82. D.B.Zax,D.K.Yang,R.A.Santos,H. Hegemann,E.P.Giannelis and E.Manias Journal of

Chemical Physics ,112,6:2945,1999 83. J.Feng L.t. Weng , C.M. Chan J.Xhie L.Li,Polymer, 42:2259, 2001 84. T.J. Bunning, R.A. Vaia ,D.W.Tomlin, M.D. Schulte , Polymer, 42:1055 , 2001 85. H.J.M. Hanley, C.D. Muzny, D.L.Ho, C.J.Glinka and E. Manias International Journal

of Thermophysics 22,5:1435, 2001 86. S. A. Body, M. M. Mortland, and C. T. Chiou, “Sorption characteristics of organic

compounds on hexadecyltrimethyl ammonium-smectite,” Soil Science Society of America Journal,vol. 52, pp. 652–657, 1988. 87. J. W. Cho and D. R. Paul, “Nylon 6 nanocomposites by melt compounding,”

Polymer, vol. 42, no. 3, pp. 1083–1094, 2001. 88. M. Zanetti and L. Costa, “Preparation and combustion behaviour of polymer/layered

silicate nanocomposites based upon PE and EVA,” Polymer, vol. 45, no. 13, pp. 4367–4373,2004 89. R. Barbosa, Effect of quaternary ammonium salts in the national bentonite clay

organophilization for the development of HDPE nanocomposites, M.S. thesis, University of Campina Grande,Campina Grande, Brazil, 2005. 90. S. Wang, Y. Hu, Q. Zhongkai, Z. Wang, Z. Chen, and W. Fan,“Preparation and

flammability properties of polyethylene/clay nanocomposites by melt intercalation method from Na+ montmorillonite,” Materials Letters, vol. 57, no. 18, pp. 2675–2678, 2003. Ph.D.Thesis, Mr. Shriram Shaligram Sonawane, U.D.C.T. N.M.U., Jalgaon Page

49

Literature Review

91. C. Zilg, P. Reichert, F. Dietsche, T. Engelardt, and R. Mulhaupt, “Pesquisadores

desenvolvem nanocomp´ ositos que atuam como cargas com diferentes finalidades,” Pl´astico Industrial, pp. 64–74, February 2000. 92. R. Barbosa, E. M. Ara´ ujo, T. J. A. Melo, and E. N. Ito, “Comparison of flammability

behavior of polyethylene/Brazilian clay nanocomposites and polyethylene/flame retardants,”Materials Letters, vol. 61, no. 11-12, pp. 2575–2578, 2007. 93. E. M. Ara ´ ujo, R. Barbosa, A. W. B. Rodrigues, T. J. A. Melo,and E. N. Ito,

“Processing and characterization of polyethylene/Brazilian clay nanocomposites,” Materials Science and Engineering A, vol. 445-446, pp. 141–147, 2007. 94. E. M. Ara ´ujo, R. Barbosa, A. D. Oliveira, C. R. S. Morais,T. J. A. deM´elo, and A.

G. Souza, “Thermal and mechanical properties of PE/organoclay nanocomposites,” Journal of Thermal Analysis and Calorimetry, vol. 87, no. 3, pp. 811–814,2007. 95. E. M. Ara ´ ujo, K. D. Araujo, and T. R. Gouveia, “Physical properties of nylon

66/organoclay nanocomposites,” Materials Science Forum, vol. 530-531, pp. 702– 708, 2006. 96. E. M. Ara ´ ujo, T. J. A. M´elo, L. N. L. Santana, et al., “The influence of organo-

bentonite clay on the processing and mechanical properties of nylon 6 and polystyrene composites,” Materials Science and Engineering B, vol. 112, no. 2-3, pp. 175–178, 2004. 97. E. M. Ara ´ ujo, R. Barbosa, C. R. S. Morais, L. E. B. Soledade,A. G. Souza, and M.

Q. Vieira, “Effects of organoclays on the thermal processing of pe/clay nanocomposites,” Journal of Thermal Analysis and Calorimetry, vol. 90, no. 3, pp. 841–848,2007. 98. H. Qin, Q. Su, S. Zhang, B. Zhao, and M. Yang, “Thermal stability and flammability

of polyamide 66/montmorillonite nanocomposites,” Polymer, vol. 44, no. 24, pp. 7533–7538,2003. 99. F. Chavarria and D. R. Paul, “Comparison of nanocomposites based on nylon 6 and

nylon 66,” Polymer, vol. 45, no. 25, pp.8501–8515, 2004. X. Liu, Q. Wu, and L. A. Berglund, “Polymorphism in polyamide 66/clay nanocomposites,” Polymer, vol. 43, no. 18, pp. 4967–4972, 2002.

100.

E. M. Araujo,1 K. D. Araujo,1 R. A. Paz,1 T. R. Gouveia,1 R. Barbosa,1 and E. N. Ito2 “Polyamide 66/Brazilian Clay Nanocomposites”, Hindawi Publishing Corporation

101.

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