Clay reinforcement

Wong et al. [41] showed that sodium montmorillonite imparted a better thermal stability to polyvinylidene difluoride-polyethylene (PE) glycol polymers than did organic montmorillonite. They showed that ethyl-3-methylimidazolium tetrafluoro-borate-functionalized montmorillonite greatly enhanced the thermal stability of the polymer. Liu et al. [42] studied the effect of various organoclays on the heat stability of poly trimethylene terephthalate. 

Ardhnananta et al. [43] showed that organoclay improved the thermal stability of ethylene vinyl acetate nanocomposites. 

Stoehler et al. [44] studied the thermal properties of polyethylene-montmorillonite nanocomposites and found evidence for accelerated formation and decomposition of hydroperoxides during the thermooxidative degradation of the nanocomposites in the range of 170°C to 200°C, as compared to unfilled polyethylene, as weU as the formation of intermolecular chemical cross-links in the nanocomposites above 200°C due to recombination reactions involving the radical products of hydroperoxide decomposition. 

The reinforcing properties of organically modified montmorillonite clay have been studied in several other polymers, including liquid crystalline polymers [45], and the suspension of montmorillonite in aqueous media containing polyelectrolytes [46]. 

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Nylon-6. Nylon-6—clay nanometer composites using montmorillonite clay intercalated with 12-aminolauric acid have been produced (37,38). When mixed with S-caprolactam and polymerized at 100°C for 30 min, a nylon clay—hybrid (NCH) was produced. Transmission electron microscopy (tern) and x-ray diffraction of the NCH confirm both the intercalation and molecular level of mixing between the two phases. The benefits of such materials over ordinary nylon-6 or nonmolecularly mixed, clay-reinforced nylon-6 include increased heat distortion temperature, elastic modulus, tensile strength, and dynamic elastic modulus throughout the —150 to 250°C temperature range. 

T.J. Pinnavaia, T. Lan, Z. Wang, H. Shi and P.D. Kaviratna, Clay-reinforced epoxy nanocomposites Synthesis, properties, and mechanism of formation. In G.-M. Chow and K.E. Gonsalves (Eds.), Nanotechnology Molecularly Designed Mlaterials, American Chemical Society, Washington, 1996, Vol. 622, p. 250. 

To clarify the mechanisms of the clay-reinforced carbonaceous char formation, which may be responsible for the reduced mass loss rates, and hence the lower flammability of the polymer matrices, a number of thermo-physical characteristics of the PE/MMT nanocomposites have been measured in comparison with those of the pristine PE (which, by itself is not a char former) in both inert and oxidizing atmospheres. The evolution of the thermal and thermal-oxidative degradation processes in these systems was followed dynamically with the aid of TGA and FTIR methods. Proper attention was paid also to the effect of oxygen on the thermal-oxidative stability of PE nanocomposites in their solid state, in both the absence as well as in the presence of an antioxidant. Several sets of experimentally acquired TGA data have provided a basis for accomplishing thorough model-based kinetic analyses of thermal and thermal-oxidative degradation of both pristine PE and PE/MMT nanocomposites prepared in this work. 

The concept of fire-retardancy is remarkably old. The Greek historian, Herodotus, in 484-431 BC recorded that the Egyptians imparted fire-resistance to wood by soaking it in a solution of alum (potassium aluminum sulfate) [Browne, 1958]. The Romans added vinegar to the alum for the same purpose. Vitruvius in the first century BC described the natural fire-retardant properties of the larch tree and some military applications of fire retardant materials such as plaster of clay reinforced with hair [Vitruvius, I960]. In 1638, Circa recorded that Italian theaters were painted with a mixture of clay and gypsum (potassium aluminum silicate and hydrated calcium sulfate) to protect them from fire. Wild was issued a British patent in 1735 for his process of treating wood with a mixture of alum, ferrous sulfate and borax (sodium tetraborate decahydrate). And Gay-Lussac in 1821 showed that a solution of ammonium phosphate, ammonium chloride and borax acts as a fire-retardant for wood. 

Varlot, K., Reynaud, E., Kloppfer, M. H., Vigier, G., and Varlet, J., Clay-reinforced polyamide preferential orientation of the montmoriUonite sheets and the polyamide crystalline lamellae, J. Polym. ScL B, 39, 1360-1370 (2001). 

Yua Yuan, Q., Misra, R. D. K. Impact fracture behaviour of clay-reinforced polypropylene nanocomposites. Polymer Vol. 47 (2006) 4421-4433. 

Pinnavaia TJ, Lan T, Kaviratna PD, WangZ, Shi H (1995) Clay-Reinforced Epoxy... 

In this chapter, the methods of producing clay-polymer nanocomposites are discussed in detail. The influence of clay reinforcement on the mechanical, thermal and physical properties of thermoplastic and thermosetting polymers is also discussed. This chapter also comprises of processing techniques of polymer nanocomposites using nanoparticles hke Al O, CaCO, TiO, ZnO and SiO as reinforcements. These materials have the potential to alter tribological, electrical and optical properties considerably. 

Figure 9.12 Differential scanning calorimetry plots for neat PP and 4 wt% clay-reinforced PP nanocomposite. Reprinted from [58] with permission from Elsevier.

Lan, T. and Pinnavaia, T. J. 1994. Clay-reinforced epoxy nanocomposites. Chemistry cf Materials 6 2216-2219. 

Clay Reinforcement in Natural Rubber on Micro and Nano Length Scales... 

The achievement of a high degree of exfoliation of layered clay minerals in nonpolar rubber matrices, such as NR, is still a major issue. This chapter presents a brief overview of studies of clay reinforcement in NR both in micro and nano scale. Although quite a lot of studies have been reported in the field of NR reinforcement with simple organoclay (OMt), plenty of scope still exists to improve the dispersion of MMT followed by property enhancement. Better dispersion and improvement in dilferent properties was observed in the case of EOMt-filled NR nanocomposites. 

A pronounced difference in stress-strain behaviour and SIC of various clay-reinforced NR nanocomposites are shown in Figure 22.9. 

Huang X, Netravali AN (2006) Characterization of Nano-clay reinforced phytagel modified soy protein concentrate. Biomacromolecules 7 2783-2789 Hill S (1997) Cars that grow on trees. New Scientist Feb 3-39... 

Pinnavaia, T. J. Lan, T. Wang, Z. Shi, H. Kaviratna, P. D., Clay-Reinforced Epoxy Nanocomposites Synthesis, Properties, and Mechanism of Formation. 

Chen F, Lou D, Yang J, Zhong M (2011) Mechanical and thermal properties of attapulgite clay reinforced polymethylmethacrylate nanocomposites. Polym Adv Technol 22 1912-1918... 

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