Polymer/clay nanocomposites characterizations

As reflected in this chapter, most of the published literature on polymer-clay nanocomposites focuses on synthesis and characterization. Future work should address is-... 

Figure 8.5 Resonance Raman spectra excited at 632.8 nm and 488.0 nm of powdered samples of PANI-ES (A), PANI-MMT samples prepared from ex situ polymerization (B) and in situ polymerization (C). (Reprinted with permission from Macromolecules, Spectroscopic Characterization of a New Type of Conducting Polymer-Clay Nanocomposite by C. M. do Nascimento, V. R. L. Constantino and M. L. A. Temperini, 35, 20. Copyright (2002) ACS)...

Morgan AB, Gilman JW, Jackson CL (2000) Characterization of Polymer-Clay Nanocomposites XRD vs. TEM in 219th ACS National Meeting. San Francisco, California... 

Masenelli-Varlot, K., Vigier, G., and Vermogen, A. 2007. Quantitative structural characterization of polymer-clay-nanocomposites and discussion of an "ideal" microstructure, leading to the highest mechanical reinforcement. 

Vaia, R. A. 2000. Structural characterization of polymer-layered silicate nanocomposites. In Polymer-Clay Nanocomposites, T. J. Pirmavaia and G. W. Beall (eds.), pp. 229-263. Chichester, U.K. John Mley Sons. 

Luo, J.-J. and Daniel, I. M. Characterization and modeling of mechanical behavior of polymer/clay nanocomposites. Composites Science and Technology 2003 63 1607-16. 

A review of methods for the detailed characterization of polymer-clay nanocomposites is beyond the scope of this chapter. Valuable information on this area can be found in several literature reviews [13, 46, 63-68]. 

This chapter is organized in the following way. First, we present some common techniques for characterizing the dispersion of nanoclays in polymer blends. The dispersion level has been shown to have a fundamental effect on the fire performance of polymer-clay nanocomposites (PCNs), as an exfoliated or intercalated polymer-clay system seems to enjoy reduced flammability. Second, the effects of nanoclays on the viscosity of polymer blends are discussed. With increased temperature in the condensed phase during combustion, most polymers (and hence polymer blends) have sufficiently low viscosity to flow under their own weight. This is highly undesirable, especially when the final products will be used in vertical orientation, because the melt can drip, having the potential to form a pool fire, which can increase fire spread. The results on thermal stability are presented next, followed by those for the cone calorimeter. The quantitative effects of nanoclays on the... 

A model poly(ethylene oxide)/laponite hybrid material, characterized by a high silicate content, was used to probe the dynamical behaviour of polymer chains at the surface with clay platelets. Such a system mimics the intercalated phases that may occur in polymer/clay nanocomposites. The segmental motions of this system were monitored over the tens of microseconds time scale by means of C and H solid-state NMR. A significant slowing down of these motions was mostly observed, as compared to the local dynamics in the amorphous phase of neat PEO. ... 

Fourier transform infrared spectroscopy (FTIR) may find a difference between the bonding in different types of nanocomposites however, the variations could be minute and hence this is an unreliable method for nanocomposite characterization [53, 54]. Nascimento et al. [55] presented for the first time the resonance Raman characterization of a polymer/clay nanocomposite formed by aniline polymerization in the presence of MMT. 

Do Nascimento GM, Crarstantino VRL, Temperini MLA (2002) Spectroscopic characterization of a new type of ctmducting polymer-clay nanocomposite. Macromolecules 35 (20) 7535-7537... 

These materials, unlike the other nanophase materials described in this chapter, are nano-sized in only one dimension and thereby act as nanoplatelets that sandwich polymer chains in composites. Mont-morillonite (MMT) is a well-characterized layered silicate that can be made hydrophobic through either ionic exchange or modification with organic surfactant molecules to aid in dispersion [5,23]. Polymer-layered silicates may be synthesized by exfoliation adsorption, in situ intercalative polymerization, and melt intercalation to yield three general types of polymer/clay nanocomposites. Intercalated structures are characterized as alternating polymer and siHcate layers in an ordered pattern with a periodic space between layers of a few nanometers [13], ExfoHated or delaminated structure occurs when silicate layers are uniformly distributed throughout the polymer matrix. In some cases, the polymer does not intercalate... 

Jo, C. and Naguib, H. E., 2007c. Processing, characterization and modeling of polymer/clay nanocomposite foams. Journal of Physics Conference Series 61 861-8. 

The theory, processes, and characterization of short fiber reinforced thermoplastics have been reviewed by De and White [31], Friedrich et al. [32], Summerscales [33], in an introductory text by Hull and Clyne [34], and in a handbook by Harper [35]. Natural fibers and composites have been reviewed by Wallenberger and Weston [36]. The introduction of new composite materials, called nanocomposites, has resulted in new materials that are being applied to various industrial applications. These materials have in common the use of very fine, submicrometer sized fillers, generally at a very low concentration, which form novel materials with interesting morphology and properties. Nanocomposites have been discussed in a range of texts including two focused on polymer-clay nanocomposites by Pinnavaia and Beall [37] and Utracki [38]. 

Polymer-clay nanocomposites are characterized by improved thermal, mechanical, barrier, fire retardant, and optical properties compared to the matrix of conventional composites, commonly called particulate microcomposites, because of their unique phase morphology deriving from layer intercalation or exfoliation that maximizes interfacial contact between the organic and inorganic phases and enhances bulk properties [8]. 

Masenelli-Varlot K., gier G., Vermogen A., Gauthier C., Cavaille J. Y. (2007), Quantitative Structural Characterization of Polymer/Clay Nanocomposites and Discussion of an Ideal Microstructure Leading to the Highest Mechanical Reinforcement. J Polym Sci Part B Polym Phys, 45,1243-51. 

The layers are characterized by a thickness of about 1 nm, and the other dimensions vary from 30 mn to several micrometres or more. Several layers are stacked in clay particles, kept together by weak van der Waals forces. The performance of polymer-clay nanocomposites strongly depends on the breaking-up of clay particles in the polymer matrix. However, the most frequently used layered silicate, MMT, is a naturally occurring 2 1 phyllosilicate, which has the same layered and crystalline structure as talc and mica but a different layer charge. A central octahedral sheet of alumina fused between two external silica tetrahedral sheets (the oxygens from the octahedral sheet also belong to the silica tetrahedral) forms the layers of the... 

In situ emulsion polymerization in aqueous solution is an effective and successful method for the synthesis of polymer-clay nanocomposites. The structure of the nanocomposites formed is usually characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD offers a convenient method to determine the position, shape and intensity of the nanofillers. The XRD patterns shows a basal (001) reflection when the spacing between the clay layers is small. However, X-rays cannot detect the (001) reflection when the layers are exfoliated in the composite. An increase in spacing between layers is correlated with an increase in the degree of exfoliation. In contrast, TEM observation gives a direct view of the internal structure, spatial distribution of the various phases and defect structures. By combining these methods, the structure of polymer nanocomposites can be determined. 

The present review aims to cover and discuss recent developments in the synthesis of polymer-clay nanocomposites through emulsion polymerization. The first part summarizes the research status of in situ emulsion polymerization performed in the presence of pristine or organically modified clays (either MMT or Laponite). Then, the chapter highlights work on the synthesis of clay-armored latexes through soap-free polymerization. It reports the state of the art in the field and presents recent advances in the synthesis and characterization of high solids content latexes stabilized by Laponite clay platelets, with particular attention to mechanistic aspects and properties of the film materials issued from... 

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