Nanomaterials nanoclays

The aforementioned frequency of the use of these nanomaterial shapes is best attributed to two factors (1) the ease with which these nanoparticle shapes can be synthesized in the laboratory and (2) the availability of these nanomaterials from commercial sources. It cannot be the aim of this review to cover all of the different nanomaterials used so far, but some of the most commonly investigated will be introduced in more detail. For zero-dimensional nanoparticles, emphasis will be put on metallic nanoparticles (mainly gold), semiconductor quantum dots, as well as magnetic (different iron oxides) and ferroelectric nanoparticles. In the area of onedimensional nanomaterials, metal and semiconductor nanorods and nano wires as well as carbon nanotubes will be briefly discussed, and for two-dimensional nanomaterials only nanoclay. Finally, researchers active in the field are advised to seek further information about these and other nanomaterials in the following, very insightful review articles [16, 36-45]. 

Two-dimensional, disc-shaped nanomaterials are the last class of nanomaterials to be discussed in more detail. Though a great variety of nanodiscs, nanosheets and nanoplatelets based on metals [256], metal oxides [257-260], graphene [261], or semiconductors [262] are frequently described in the literature, the vast majority of studies in liquid crystal systems dealt with some form of nanoclay. 

Prominent exceptions are studies on the liquid crystal phase formation and self-assembly of two-dimensional disc- or sheet-like nanomaterials such as the organization of nanodiscs or nanoplatelets into nematic, smectic, or columnar morphologies [263-270] (see Fig. 2 for an example of the self-assembly of nanoclay in aqueous suspensions) or the synthesis of CuCl nanoplatelets from ionic liquid crystal precursors as described by Taubert and co-workers [271-273]. 

The characterization of these natural or synthetic nanoclay materials is just as critical as for the nanomaterials discussed in the previous sections and should... 

Three different types of nanomaterials, based on their dimensional characteristics, are generally used to prepare polymer nanocomposites. These include nanomaterials with only one dimension in the nanometre range (e.g. nano-clay), those with two dimensions in the nanometre scale (e.g. carbon nanotubes) and those that have all three dimensions in the nanometre scale (e.g. spherical silver nanoparticles), as stated earlier. Thus nanosize thin layered aluminosilicates or nanoclays, layer double hydroxide (LDH), a large number of nanoparticles of metals and their oxides, carbon nanotubes and cellulose nanofibres are used as nanomaterials in the preparation of vegetable oil-based polymer nanocomposites. 

Nanoclays Versatile Building Blocks for Multi-Functional Composites -Nanomaterials http //www.sigmaaldrich.com/materials-science/nanomateri-als/nanoclay-building/nanoclays-montmorillonites.html sthash.6P9adFFa. dpuf... 

As a result of the existing manufacturing techniques, a great amount of nanomaterials such as nanofibers, carbon nanotubes, SiO and nanoclay is currently available and the use of fiber-reinforced polymer nanocomposites in practical applications is continuously growing. It has been reported in the literature that nanoclays account for approximately 70% of the total volume of commercially used nanomaterials [8]. 

With the development of nanomaterials concerns exist about their toxicity and health impacts. Because of the size of nanoparticulates, concerns arise about then-ability to penetrate tissue and cause harmful effects ranging from mild irritation to more serious tumor developments. In the case of nanoclays, one has to consider that nanoclays only become nanosized after incorporation and exfoUation in a polymer matrix. In a practical sense, the presence of crystalline silica, a material that may be found in clays, is probably more of a real hazard. Crystalline silica is regulated to extremely low levels in commercial day materials [112] (see also Chapter 19). 

Montmorillonite (MMT), a smectite clay, is probably the most extensively studied nanomaterial in terms of mechanical, thermal, fire retardant or crystallization behavior of polylactide, especially when these nanoparticles are organically modified allowing the achievement of intercalated and exfoliated nanocomposites.These nanocomposites show enhanced properties as compared to microcomposites and pristine polymer. However, biodegradation and hydrolytic degradation of PLA in the presence of nanoclays has been investigated to a small extent. 

The Singapore company NanoMaterials Technology Pte. Ltd. supplies nanosize calcium carbonate to the PVC industry and says that price is not a problem, as the nanofiller only costs half as much as chlorinated polyethylene impact modifiers. Adding 2 to 4% of nanoclay will produce a six-fold increase in the impact strength of PVC pipe. The increase is attributed to a change in crystallinity. 

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