Sodium montmorillonite nanocomposites

The results are reported of an in depth study of the structure, thermal properties, dynamic mechanical properties, flammability and smoke properties of melt blended PVC-sodium montmorillonite nanocomposites. Investigative properties employed included X-ray diffraction, TEM, TGA, DMA and cone calorimetry. The effects of clay loading, DOP concentration, annealing, blending time and molec.wt. on the formation of the composites are discussed and fire properties of PVC-organically modified clay and PVC-sodium clay nanocomposites are presented and discussed. 15 refs. USA... 

Z. S. Kalkan and L. A. Goettier, In situ polymerization of polyamide 66 nanocomposites utilizing interfacial polycondensation. II. Sodium montmorillonite nanocomposites. Polymer Engineering and Science, 49 (2009), 1825-31. 

MELT INTERCALATION/EXFOLIATION OF POLYSTYRENE - SODIUM MONTMORILLONITE NANOCOMPOSITES USING SULFONATED POLYSTYRENE... 

The morphology of rubber-based nanocomposites also seems to change in the presence of compounding ingredients [89, 90]. HNBR, when melt-compounded with organo-modified sodium montmorillonite clays (o-MMTs) prior to sulfur curing, resulted in the formation of nanocomposites with exfoliated or intercalated structures. In stark contrast, under similar conditions HNBR compounded with unmodified sodium montmorillonite clays (NA) formed microcomposites [90]. This was traced to its reactivity with the sulfur in the presence of amine-type organomodifiers. 

Wu, J. Lerner, M. (1993) Structural, Thermal, and Electrical Characterization of Layered Nanocomposites Derived from Sodium-Montmorillonite and Polyethers. Chem. Mater. Vol.5, No.6, pp.835-838... 

As mentioned previously, because of the polycationic nature of chitosan in acidic media, the biopolymer may be intercalated in sodium montmorillonite through cation exchange and hydrogen-bonding processes, the resulting nanocomposites showing interesting structural and functional properties. 

A modified melt blending method has been developed for preparing exfoliated nanocomposites of poly(m-xylylene adipamide) with sodium montmoril-lonite [100]. There, an aqueous solution of sodium montmorillonite was blended with the polymer in a twin-screw extruder. This kind of mixing ensures that the silica nanoparticles are exfoliated in the polymer matrix through fixing the nanoparticles within the polymer matrix just as they are in water. Oxygen permeation data show enhanced the barrier properties of the nanocomposites. 

Sodium montmorillonite (Na-MMT) was originally modified with pro-tonated amino acids with different numbers of carbon atoms and subsequently swollen with e-caprolactam. Then it underwent polymerization to produce nylon-6 polymer-clay nanocomposite [18]. Later, this technique was also extended to manufacture other thermoplactics. One advantage of this in-situ polymerization technique is the tethering effect, which enables the organic chemical such as 12-aminododecanoic acid (ADA) situated at the surface of the nanoclays to link with nylon-6 polymer chains during polymerization. 

The first polypropylene/clay nanocomposite made by intercalative polymerization was reported by Qi et al. Sodium montmorillonite was ion exchanged with (hexadecyl/ octadecyl)trimethylammonium, then vacuum-dried at llO C. The organoclay was ground... 

Two types of MMT-sodium montmorillonite (Cloisite Na, Southern Clay) and an organomodified montmorillonite (Cloisite 30B) -were used to prepare MMT-PFA nanocomposites, denoted as NaMMT-PFA and 30BMMT-PFA, respectively. 

Pandis et al. [101] examined the morphology, microhardness, and electrical properties of melt-mixed or compression-molded composites based on conductive polypyrrole dispersed into a nonconductive polypropylene matrix either as a pure component or as a nanocomposite with sodium montmorillonite. The effects of the polypyrrole and montmorillonite content on the properties of the composites were studied, and the results are discussed in terms of microstructure. 

Other thermally stable surfactants have been used in the preparation of organoclays to produce PS nanocomposites [57]. Triphenylhexadecylstibonium trifluoromethylsulfonate (Table 3.4) was prepared with sodium montmorillonite to prepare polystyrene nanocomposites by bulk polymerization. The organoclay was not uniformly distributed throughout the polymer matrix, but there was evidence of polymer intercalation and a small amount of clay exfoliation (Figure 3.13). The nanocomposite showed enhanced thermal stability. 

Wu J, Lemer MM (1993) Structural, thermal, and electrical characterization of layered nanocomposites derived from sodium-montmorillonite and polyethers. Chem Mater 5 (6) 835-838... 

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