Clays intercalated with nanoparticles

In the case of LASIP with clay nanoparticles, polystyrene was grafted using a DPE coinitiator. The montmorillonite clay surface and intergallery interfaces were intercalated with 1,1-diphenylethylene (DPE) modified to be an organic cation as shown in Fig. 4. Its intercalation was confirmed by a series of characterization methods including X-ray diffraction (XRD), FT-IR spectroscopy, TGA, and XPS. The results showed a complete replacement of... 

In order to improve the textural properties of particle-clay nanohybrids, bulky organic cations are intercalated as a kind of template into particle-intercalated clays before stabilization procedures. Intercalation of the organic cations results in the removal of some of the intercalated nanoparticles and/or in their rearrangement. Subsequent calcination leads to formation of additional pore space that is highly correlated to the geometry and size of the templates. This technique allows fine tuning of textural properties in the preparation of particle-clay nanohybrids. The clay nanohybrids intercalated with metals, oxides, and complexes have a broad range of applications. In particular, metal oxide particle-pillared clays have excellent potentials as catalysts, catalyst supports, selective adsorbents, etc. " ... 

The intercalation of Au nanoparticles in CTAB/clay composite by sonication showed a completely different distribution of Au nanoparticles in the clay matrix. SAXS demonstrates that the interlamellar space increases up to 3.17 nm and 7.3 nm (Fig. ID). However, the XRD (Fig. ID) and TEM (Fig. 2C) show the local incorporation of only small amounts of Au nanoparticles in the clay matrix with a partial agglomeration. 

Valarezo, E., Tammaro, L., Gonzalez, S., Malagon, O., and Vittoria, V. (2013) Fabrication and sustained release properties of poly(e-caprolactone) electrospun fibers loaded with layered double hydroxide nanoparticles intercalated with amoxicillin. Appl. Clay Set, 72, 104-109. 

Numerous thermoplastic and thermosetting pol3miers have been applied for producing nanocomposites using the in situ approach however, for the first time, it was used for clay/polyamide 6 nanocomposites. In general, the nanoparticles of filler are premixed with the liquid monomer or its solution. When layered nanofiller such as clay (swollen by means of modification) is added, the pol5mierization occurs within sheet intercalated with monomer. Then either radiation, heat or an initiator tri er the reaction of pol5mierization [57]. 

It was also noticed by the same authors19 that the incorporation of the OMMT in EVA instead of PA6, keeping constant the global composition, led to a strong decrease in heat released, but with a different evolution of HRR as a function of time. This was ascribed to different morphologies of clays (mixed intercalated/exfoliated versus completely exfoliated) for the polymer blend. Consequently, the formulation process of complex FR systems involving polymer blends and made up of nanoparticles in combination with FRs seems crucial. 

These clays have been hybridized with diverse structural types of components such as nanoparticles, clusters, complex compounds, polymers, molecules, and ions. Their potential apphcations are found in many fields as inorganic catalysts, adsorbents, ceramics, coatings, and even drug delivery carriers. Various preparation methods have been developed such as pillaring, intercalation, and delamination techniques. The representative examples include organic-clay hybrids," metal oxide-pillared clays, " and bioclay hybrids. ... 

The influence of neutral polymer polyethylene glycol and two surfactants with different charge, anionic sodium dodecylsulfate and cationic cetyltrimethylammonium bromide, on the intercalation of pre-formed Au nanoparticles into a clay matrix under ultrasonic treatment has been investigated. The polymer (surfactant) addition has been used to modify the active surface area of NaLmontmorillonite and to change the interlamellar space between the clay layers. Then, intercalated polymer (surfactant) in clay composites has been successfully replaced by Au nanoparticles under sonication. 

The intercalation of nano-gold into clay layers comprised two steps. The first step was the intercalation of the polymer (surfactant) into clay matrix for increasing the interlamellar space between the clay layers. The second step was the replacement of the intercalated polymer (surfactant) by Au nanoparticles by adding different amounts of nanoparticles to the polymer (surfactant)/clay composite. Both steps were performed by applying ultrasonic irradiation. The solution was sonicated at 20 kHz, 500 W. The intercalation progress was monitored as a function of time. The precipitated nano-Au/intercalated product was separated by centrifugation, washed with water and dried under vacuum overnight. After that samples were calcined in air at 800 °C for 4 h. 

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]. 

The mixing of the nanoparticle with the polymer requires an intercalation process of the macromolecule into the clay galleries gap. This is a diffusion-controlled process that requires long contact times between the polymer and the clay under the pressure produced inside the extruder. The intercalation process leads to the exfoliation of the clay. However, low screw speeds and long residence times in... 

Since nanoparticles in PNC are orders of magnitude smaller than conventional reinforcements, the models developed for composites are not applicable to nanocomposites. However, development of a universal model for PNC is challenging since the shape, size, and dispersion of the nanoparticles vary widely from one system to another. On the one hand, exfoliated clay provides vast surface areas of solid particles (ca. 800 m /g) with a large aspect ratio that adsorb and solidify a substantial amount of the matrix polymer, but on the other hand, the mesoscale intercalated clay stacks have a much smaller specific surface area and small aspect ratio. However, in both these cases the particle-particle and particle-matrix interactions are much more important than in conventional composites, affecting the rheological and mechanical behavior. Thus, the PNC models must include the thermodynamic interactions, often neglected for standard composites. 

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. 

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