Nylon-6/clay nanocomposites synthesis

Nanoclays. Nanocomposites are materials that contain nanofillers, or fillers of nanometer dimensions. The successful synthesis of nylon-clay nanocomposites (57-59) ushered in nylon nanocomposites that could attain high modulus, heat distortion temperature, dimensional stabiUty, impermeabiUty, and strength with only a few percent modified clay nanofillers. Although it has been long known that poljuners could be mixed with appropriately modified clay minerals and synthetic clays, the field of polymer-layered silicate nanocomposites has gained... 

Epoxy-clay nanocomposites from epoxide precursors have been investigated by research groups at Michigan State University [34-40], Cornell University [41], and Case Western Reserve University [42,43]. In general, the synthesis is similar to that of Nylon-6 and PS... 

A nylon-clay hybrid (nanocomposite NCH) was originally developed by the authors and was the first polymer nanocomposite to be used practically. Since 1990, when it was first used, various studies and analyses of it have been reported. An excellent review was published in 2003 [1]. In the present review, which focuses on the authors studies, details on the NCH that we reported initially and further developments in polypropylene and polyethylene will be described. In Sect. 2, comprehensive classifications of the production methods developed previously will be described, according to the synthesis method employed. Thereafter, nylon will be discussed in Sect. 3, polyolefin in Sect. 4, and renewable polymer (green polymer) will be discussed in Sect. 5. 

Figure 6.7 Schematic illustration for synthesis of nylon-6/clay nanocomposites/...

The topic of polymer nanocomposites pertains to the synthesis, characterization, and applications of polymer materials with at least one or more dimensions less than 100 nm. According to the Rayleigh criterion, the maximum resolution or the minimum detectable size achievable was believed to be half the wave length of light, that is, 200 nm. The first clay nanocomposite was commercialized by Toyota with a belt cover made of a nylon-6 matrix filled with 5% clay. General Motors commercialized the first exterior trim application of nanocomposite in their 2002 mid-sized vans. 

The model illustrated in Figure 2 summarizes the overall mechanism for formation of epoxy polymer - clay nanocomposites. Upon solvation of the organoclay by the epoxide monomers, the gallery cations reorient from their initial monolayer, lateral bilayer, or inclined paraffin structure to a perpendicular orientation with epoxy molecules inserted between the onium ions. A related reorientation of alkylammonium ions has been observed previously for e-caprolactam intercalated clay intermediates formed in the synthesis of Nylon-6 -exfoliated clay nanocomposites (9). Thus, the ability of the onium ion chains to reorient into a vertical position in order to optimize solvation interactions with the monomer may be a general prerequisite for pre-loading the clay galleries with sufficient monomer to achieve layer exfoliation upon intragallery polymerization. 

Among the variety of inorganic solids e.g. silica, iron oxides, titanium dioxide, metals), clay minerals have recently attracted considerable attention. Indeed, polymer-clay nanocomposites (PCNs) have been the topic of extensive research worldwide since scientists at the Toyota Central Research laboratories reported 10 years ago that the incorporation of small amounts of montmorillonite (MMT) into nylon-6 resulted in a remarkable enhancement of the thermal and mechanical properties of the nanocomposite material. Whereas there has been a tremendous number of studies on the synthesis, properties and applications of polymer-clay nanocomposites in the recent literature, surprisingly only a small number of reports have dealt with emulsion polymerization. 

A new composite material was introduced in 1987 with the discovery of a nylon-6/clay hybrid (NCH) [201]. The hybrid was prepared by the in situ thermal polymerization of s-caprolactam with 8% or less montmorillonite, the clay material containing 1-nm thick exfoliated aluminosilicate layers. It exhibited a truly nanometer-sized composite of nylon-6 and layered aluminosilicate. Figure 2.14 depicts conceptually the NCH synthesis and its fine structure. The NCH exhibited high modulus, high strength, and good gas-barrier properties. The unique and superior properties led to the commercialization of NCH. It has also created a new class of nanocomposites and worldwide interest. 

Steed JW, Atwood JL (2000) Supramolecular chemistry. Wiley, New York Tomasik P (1985) Pyridine-metal complexes (Newkome GR, Strekowski L). Wiley, New York Usuki A, Kojima Y, Kawasumi M, Okada A, Fukushima Y, Kurauchi T, Kamigaito O (1993) Synthesis of nylon 6-clay hybrid. J Mater Res 8 1179 Vaia RA, Giaimelis EP (2001) Liquid crystal polymer nanocomposites direct intercalation of thermotropic liquid crystalline polymers into layered silicates. Polymer 42 1281 Villemore G (1990) Effect of negative surface-charge densities of smeetite clays on the adsorption isotherms of racemic and enantiomeric tris (2,2 -bipyridyl) ruthenium(ii) chloride. Clays Clay Miner 38 622... 

After it was verified that nylon 6 could be mixed with clay to make nanocomposites with dramatically improved performance characteristics, the same synthesis techniques were applied to other types of nylon resins. 

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