Silicate delamination

XRD was used to investigate the spacings of silicate layers of montmorillonite (from 1.9 to 4nm) in PP/montmorillonite (MMT) nanocomposites prepared by in situ graft-intercalation in the presence of acrylamide [331]. Similarly, XRD and TEM were used to study the dispersibility of PP/MMT nanocomposites prepared by melt intercalation using organo-montmorillonite and conventional twin screw extrusion [332]. Various delaminated and intercalated polymer (PA6, PA 12, PS,... 

Figure 7 shows the representative bright field HRTEM images of nanocomposites of NR and unmodified montmorillonite (NR/NA) prepared by different processing and curing techniques. It is apparent that the methodology followed to prepare the nanocomposites by latex blending facilitates the formation of exfoliated clay structure, even with unmodified nanoclays. It has been reported in the literature that hydration of montmorillonite clay leads to extensive delamination and breakdown of silicate layers [94, 95]. It has also been shown that NA disperses fully into the individual layers in its dilute aqueous dispersion (clay concentration <10%)... 

In the case of mica-type layered silicates it has been recently demonstrated that nanocomposites (both intercalated and delaminated) can be synthesized by direct melt intercalation even with high molecular weight polymers [7-18]. This synthetic method is quite general and is broadly applicable to a range of commodity polymers from essentially non-polar polystyrene, to weakly polar polyethylene terephthalate), to strongly polar nylon. Nanocomposites can, therefore, be processed using currently available techniques such as extrusion, thus lowering the barrier towards commercialization. 

In addition, two end-tethered delaminated hybrid systems prepared by in-situ polymerization - (a) Poly( -caprolactone)-montmorillonite (PCLC) and (b) nylon-6-montmorillonite (NCH) - wherein the polymer chains are end-tethered to the silicate surface via cationic surfactants [54] (Fig. 20), were also studied. 

Fig. 19. The steady-shear rheological behavior for a series of delaminated nanocomposites ol polydimethylsiloxane with dimethyl ditallow montmorillonite at 25 °C. The steady-shear viscosity shows an increase with respect to that of the pure-polymer at low shear rates but still obeys Newtonian type behavior, even at the highest silicate loadings examined. From Ref. [5].

ASP072,101,102,170,200,400P, 600,602,672, NC, Buca, Catalpo - hydrous aluminum silicate, spray-dried or highly pulverized powders. ASP 101 is stearate coated and ASP NC is delaminated Santitone 5, 5HB, Special, SP-33, Whitetex - calcinated kaolins... 

Muscovite Mica 6915,6912,6908,6905 - grades of different particles sizes for plastics and coatings SG-70, SG-90 - hydrous potassium aluminum silicate produced by patented process which gives high brightness delaminated muscovite mica for joint compounds, adhesives, sealants, coatings... 

XRD analysis of completely cured nanocomposite samples also lacked the silicate (001) reflections as shown in Figs. 12 and 13 for OMTS-DGEBA-BMDA and OMTS-DGEBA-NMA, respectively. The absence of the silicate (001) reflections in the cured nano composites showed that the delamination and dispersion of... 

Fig. 27. Steady-shear viscosity as a function of shear rate for a series of delaminated hybrids of poly(dimethylsiloxane) with dimethylditallow-MMT with varying levels of silicate loading at T=28 °C...

At present, MCM-22 and ferrierite represent the only two described examples of zeolites, which can be synthesized in the layered form and further transformed to 3-D crystal structures. Delamination of ferrierite led to the formation of ITQ-6 and ITQ-20 [52], while ITQ-2 can be prepared from the lamellar precursor of MCM-22 [15]. Not only aluminum but also titanium was incorporated into the siliceous ITQ-6 and evaluated in acid and oxidation reactions [52,53]. 

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