Nanoparticles organoclays

Hb and GOx, respectively. The variation in nanopartide size showed a direct correlation with the respective molecular dimensions of the different proteins, suggesting that each nanoparticle comprised a single biomolecule enveloped by a continuous condensed sheet of organoclay oligomers, one unit cell layer in thickness. 

Higher-order organization of the organoclay-wrapped protein nanoparticles was achieved by tailoring the organic functionalities attached to the organoclay oligomers. 

In this work, tests were also conducted for other polymers with different type or loading of nanoparticles. These materials are an ethylene-vinyl acetate (EVA) nanocomposite with 5 wt % organoclay by Kabelwerk EUPEN AG/Belgium, and a PBT nanocomposite with 5 wt % Sepiolite. The samples size is the same as the one for PA6 (i.e., 100 x 100 x 6 mm). Similar to the PA6 tests, three external heat fluxes (40, 50, and 60kW/m2) were used with duplicated tests at each heat flux level. 

Thus, from the results of the kinetic analyses of TGA data for both antioxidant-stabilized and unstabilized PE and PE-MMT nanocomposite it follows that the organoclay nanoparticles can exert two counteracting effects influencing the thermal-oxidative stability of the PE-MMT nanocomposite ... 

Nanoparticles or nanofillers are collective terms for modified layered silicates (organoclay), graphite nanoflakes, carbon nanotubes, and a number of materials dispersed in the polymer matrix, when the particles size is in order of nanometers (one thousands of micron), or tens of nanometers. A plastic filled with nanoparticles, typically in the range of 2-10% (w/w) is called a nanocomposite. 

Both intercalated and exfoliated nanocomposites, containing 3-5% of nanoparticles (w/w), reportedly show better or comparable flame resistance compared with plastics filled up to 30-50% with traditional flame retardants. Another way to increase flame retardancy is to combine ATH or magnesium hydroxide with organo-clays. It was reported that organoclays and some classical flame retardants, such as brominated compounds, showed a synergism between them [13]. 

Fig. 13.12 Polymer nanocomposites containing spherical silica nanoparticles in vinyl ester (left) and exfoliated organoclay...

Polypropylene (PP) is one of the most widely used plastics in large volume. To overcome the disadvantages of PP, such as low toughness and low service temperature, researchers have tried to improve the properties with the addition of nanoparticles that contains p>olar functional groups. An alkylammonium surfactant has been adequate to modify the clay surfaces and promote the formation of nanocomposite structure. Until now, two major methods, i.e., in-situ polymerization( Ma et al., 2001 Pirmavaia, 2000) and melt intercalation ( Manias et al.,2001) have been the techniques to prepare clay/PP nanocomposites. In the former method, the clay is used as a catalyst carrier, propylene monomer intercalates into the interlayer space of the clay and then polymerizes there. The macromolecule chains exfoliate the silicate layers and make them disperse in the polymer matrix evenly. In melt intercalation, PP and organoclay are compounded in the molten state to form nanocomposites. 

EE Eang, Y.D. Liu, H.J. Choi, Synthesis and electrorheological characteristics of polyaniline/organoclay nanoparticles via Pickering emulsion polymerization, Smart Mater. Struct., 2010,19,124002 (6pp). 

Polymer blends containing nanoparticles provide a route to balance the properties when prepared using an appropriate mixing protocol. Nonetheless, the improvement in the blend properties is very specific to the blend components and type of nanoparticle. For example, organoclays and silica reduce elongation at break, while functionalized carbon nanotubes have been shown to increase the tensile ductility... 

Organoclays have also similar effects on polymers thermal stability and in this case the achieved clay dispersion (intercalated-exfoliated) as well as the used modifier can also alter thermal decomposition of polymers. Cationic compounds used for organomodification of MMT have a negative effect in thermal degradation while the exfoliated stmcture due to the finer dispersion of the clay nanoparticles can lead to thermal stabilization than intercalated structure. 

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