Nanocomposite preparation

The last matrix type described in this section, also frequently used in nanocomposite preparation, is PDMS filled with various fillers such as (l x) Pb(Mg]/3Nb2/3) 03-xPbXi03 (PMN-PT) (Xu et al., 2013), NaNbOj (Jung et al., 2011), and BiFeOs (Murakami et al., 2013) nanoparticles. These nanocomposites have been successfully used as nanogenerators with the capabihty for mechanical energy harvesting. 

In this case, various matrices have been mentioned in relation to mechanical energy harvesting. Their further utilization depends on possible real applications. Therefore, various types have been investigated, and their promising behaviors were estimated. 

Materials used as energy harvesters usually have highly ordered stmctures to obtain the highest electrical output. Therefore, their fabrication techniques have to be precise. 

2013 Rahman and Chung, 2013). These are generally facile, reproducible, and financially undemanding therefore, they are frequently applied. 

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Al-Mulla, E.A.J., Yunus, W.M.Z., Ibrahim, N.A. and Abdul Rahman MZ. 2010c. Epoxidized palm oil plasticized polylactic add /fatty nitrogen compounds modified clay nanocomposites preparation and charaderizations. Polymers and Polymer... 

Zhenyang, Y., Jingbo, Y., Shifeng, Y., Yongtao, X., Jia, M. and Xuesi, G. 2007. Biodegradable poly(L-lactide)/poly(3-caprolactone)-modified montmorillonite nanocomposites Preparation and characterization. Polymer 48 6439-6447. 

Due to the TO structure of the clay, the interlayer H-bonding is very strong. This hinders the intercalation of any molecule or chain into the gallery. Hence, the kaolinite clay cannot be used for nanocomposite preparation. 

SCHEME 2.1 The melt-intercalation method for nanocomposite preparation. 

ENGAGE is an ethylene-octene copolymer. Ray and Bhowmick [70] have prepared nanocomposites based on this copolymer. In this study, the nanoclay was modified in situ by polymerization of acrylate monomer inside the gallery gap of nanoclay. ENGAGE was then intercalated inside the increased gallery gap of the modified nanoclay. The nanocomposites prepared by this method have improved mechanical properties compared to that of the conventional counterparts. Preparation and properties of organically modified nanoclay and its nanocomposites with ethylene-octene copolymer were reported by Maiti et al. [71]. Excellent improvement in mechanical properties and storage modulus was noticed by the workers. The results were explained with the help of morphology, dispersion of the nanofiller, and its interaction with the mbber. 

The first nanocomposite prepared by Toyota Group of Japan was based on nylon 6. In situ polymerization of caprolactum inside the gallery of 5% MMT resulted in the first nylon 6-clay nanocomposite. Besides nylon, polypropylene (PP) is probably the most thoroughly investigated system. Excepting the study of the various properties, theoretical aspects and simulations have also... 

FIGURE 3.3 (a) Transmission electron microscopic (TEM) image of acrylic rubber (ACM)-siUca hybrid nanocomposite synthesized from 10 wt% of tetraethoxysilane (TEOS). (From Bandyopadhyay, A., Bhowmick, A.K., and De Sarkar, M., J. Appl. Polym. Sci., 93, 2579, 2004. Courtesy of Wiley Interscience.) Transmission electron microscopic (TEM) photographs of acrylic rubber (ACM)-silica hybrid nanocomposites prepared from (b) 30 wt% and (c) 50 wt% tetraethoxysilane (TEOS) concentrations. (From Bandyopadhyay, A., Bhowmick, A.K., and De Sarkar, M., J. Appl. Polym. Sci., 93, 2579, 2004. Courtesy of Wiley InterScience.)... 

FIG. 10 Compressive (a) yield strength and (b) moduli for the pristine epoxy polymer and the exfoliated epoxy-clay nanocomposites prepared from three different kinds of organomontmorillonites. (From Ref. 40.)... 

FIG. 11 Stress-strain curves for (a) a pristine polyurethane elastomer (b) a polyurethane-clay nanocomposite prepared from organomontmorillonite (5 wt%). (From Ref. 66.)... 

FIG. 12 X-ray diffraction patterns of poly(dimethylsiloxane)-clay nanocomposites prepared from dimethyl ditallowammonium-exchanged montmorillonite as a function of the weight ratio of water to silicate. (From Ref. 67.)... 

Nylon-6-clay nanocomposites were also prepared by melt intercalation process [49]. Mechanical and thermal testing revealed that the properties of Nylon-6-clay nanocomposites are superior to Nylon. The tensile strength, flexural strength, and notched Izod impact strength are similar for both melt intercalation and in sim polymerization methods. However, the heat distortion temperature is low (112°C) for melt intercalated Nylon-6-nanocomposite, compared to 152°C for nanocomposite prepared via in situ polymerization [33]. 

XRD was used to investigate the spacings of silicate layers of montmorillonite (from 1.9 to 4nm) in PP/montmorillonite (MMT) nanocomposites prepared by in situ graft-intercalation in the presence of acrylamide [331]. Similarly, XRD and TEM were used to study the dispersibility of PP/MMT nanocomposites prepared by melt intercalation using organo-montmorillonite and conventional twin screw extrusion [332]. Various delaminated and intercalated polymer (PA6, PA 12, PS,... 

Applications of sol-gel-processed interphase catalysts. Chemical Reviews, 102, 3543-3578. Pierre, A.C. (2004) The sol-gel encapsulation of enzymes. Biocatalysis and Biotransformation, 22, 145-170. Shchipunov, Yu.A. (2003) Sol-gel derived biomaterials of silica and carrageenans. Journal of Colloid and Interface Science, 268, 68-76. Shchipunov Yu.A. and Karpenko T.Yu. (2004) Hybrid polysaccharide-silica nanocomposites prepared by the sol-gel technique. Langmuir, 20, 3882-3887. 

Fig. 9.4 Bright field TEM images of PLA-based nanocomposites prepared with (A) MMT-C1gH3N+, (B) MMT-Clg(CH3)3N+and (C) MMT-2Clg(CH3)2N+. The dark entities are the cross section and/ orfaceofthe intercalated-and-stacked silicate layers and the bright areas are the matrix. Reprinted from [18], 2006, Wiley-VCH.

In 2002, Lee et al. [51] reported the biodegradation of aliphatic polyester-based nanocomposites under compost. Figure 9.13(A, B) represent the clay content dependence of biodegradation of APES-based nanocomposites prepared with two different types of MMT clays. They assumed that the retardation of biodegradation was due to the improvement of the barrier properties of the aliphatic APSE after nanocomposite preparation with clay. However, there are no data about permeability. 

Recently, Yamada and Okamoto et al. [52-54] first reported the biodegradability of neat PLA and PLA-based nanocomposites prepared with trimethyl octadecylammo-nium-modified MMT (MMT-Ci8(CH3)3N+) with a detailed mechanism. The compost... 

K. Okamoto and M. Okamoto also investigated the biodegradability of neat PBS before and after nanocomposite preparation with three different types of OMLF. They used alkylammonium or alkylphosphonium salts for the modification of pristine layered silicates, and these surfactants are toxic for microorganisms [56]. 

PDMS nanocomposites with layered mica-type silicates were also reported.374 A two-step sol-gel process of the in situ precipitation of silica led to the development of siloxane-based nanocomposites with particularly high transparencies.3 5 Some unusual nanocomposites prepared by threading polymer chains through zeolites, mesoporous silica, or silica nanotubes were reviewed.3 6 Poly(4-vinylpyridine) nanocross-linked by octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane was reported.377... 

M. Alexandre, P. Dubois, Polymer-layered silicate nanocomposites Preparation, properties and uses of a new class of materials, Materials Science and Engineering, vol. 28, pp. 1-63, 2000. 

M. Alexandre, Ph. Dubois, Polymer-layered silieate nanocomposites preparation,... 

J.-L. Bobet, E. Grigorova, M. Khrussanova, M. Khristov, R Stefanov, P. Peshev, D. Radev, Hydrogen sorption properties of graphite-modified magnesium nanocomposites prepared by ball-milling, J. Alloys Compd. 366 (2004) 298-302. 

Yang Y, Lu Y, Lu M, Huang J, Haddad R, Xomeritakis G, Liu N, Malanoski AP, Sturmayr D, Fan H, Sasaki DY, Assink RA, Shelnutt JA, van Swol F, Lopez GP, Bums AR, Brinker CJ. Functional nanocomposites prepared by self-assembly and polymerization of diacetylene surfactants and silicic acid. J Am Chem Soc 2003 125 1269-1277. 

Alexandre, M., Dubois, P. (2000). Polymer-layered silieate nanocomposites preparation, properties and uses of a new elass of materials. Material Science and Engineering, 28, 1-11. 

Morphological structures and properties of a series of poly(ethyl acrylate)/clay nanocomposites prepared by the two distinctively different techniques of in situ ATRP and solution blending were studied by Datta et al. [79]. Tailor-made PNCs with predictable molecular weights and narrow polydispersity indices were prepared at different clay loadings. WAXD and studies revealed that the in situ approach is the better option because it provided an exfoliated morphology. By contrast, conventional solution blending led only to interlayer expansion of the clay gallery. 

The dispersion behavior of organoclay affected the visual appearance of the hybrid composites (Fig. 6a, b). The composites containing Si particles predominantly as a finely dispersed phase were transparent, e.g., PNCI2 [nanocomposite prepared in... 

The effect of the microstructure of acrylic copolymer/terpolymer on the properties of silica-based nanocomposites prepared by the sol-gel technique using TEOS has been further studied by Patel et al. [144]. The composites demonstrate superior tensile strength and tensile modulus with increasing proportion of TEOS up to a certain level. At a particular TEOS concentration, the tensile properties improve with increasing hydrophilicity of the polymer matrix and acrylic acid modification. 

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