Montmorillonite exchange

Table 8.2. Replacement of exchangeable calcium from 1 mmol of montmorillonite exchange sites by a constant amount (1 mmole of ion charge) of barium or ammonium, at varying replacing-cation concentrations3...

K10 montmorillonites exchanged with different cations, dried at 120°C or calcined at 550°C, are used as catalysts in Diels-Alder reactions of methyl and (-)-menthyl acrylates with cyclopentadiene. In general, calcined clays give rise to better conversions and selectivities. Zr(IV) and specially Ti(IV) clays display the best catalytic activities. However, the best asymmetric induction is achieved with Cr(lll) and Ca(ll) calcined clays. Clays containing easily reducible cations behave differently due to the cyclopentadiene polymerization via radical cations. 

Clays [2] and zeolites [3] have been reported as good catalysts for Diels-Alder synthesis. Recently, we have studied the Diels-Alder cycloaddition between methyl acrylate (1) and cyclopentadiene (2) (Figure 1) and have shown that the solvent [4], the calcination of the solid [5] and the exchanged cation [6] play a decisive role. We now report the results obtained from the reactions of cyclopentadiene with methyl and (-)-menthyl acrylates, catalysed by K10 montmorillonites exchanged with different cations and dried at 120°C or calcined at 550°C. 

Boufatit, M, Ait-Amar, H. McWhinnie, W. R. (2007). Development of an Algerian material montmorillonite clay. Adsorption of phenol, 2-dichlorophenol and 2,4,6-trichlorophenol from aqueous solutions onto montmorillonite exchanged with transition metal complexes. Desalination, vol. 206, pp. 394-406. ISSN 0011-9164. Burns, S. E., Bartelt-Hunt, S. L. Smith, J. (2003). Sorption and permeability of gasoline hydrocarbons in organobentonite porous media. Journal of Hazardous Materials, vol. 96, pp. 91-97. ISSN 0304-3894. 

Primary alkyl amines, when exposed to acidic medium, protonate the amine function resulting in the formation of alkylammonium ions. Montmorillonite exchanged with long-chain alkylammonium ions can be dispersed in polymer matrix. 

Table 3 Adsorption capacities of montmorillonite (exchanged with various cations from aqueous solutions)...

The exact same process with the same equipment that was employed to produce the nylon 6 nanocomposites was employed with the amorphous polyamide. The same procedure as outlined above with the nylon 6 nanocomposites was used to characterize the amorphous polyamide nanocomposites. Cloisite 30B and the organomontmorillonite prepared with trimethyl hydrogenated tallow quat demonstrated excellent exfoliation. Cloisite 20A was not as effective in exfoliation. The mechanical performance of the montmorillonite exchanged with trimethyl hydrogenated tallow quat had the superior Young s modulus. 

The reduced exchange capacity montmorillonites exchanged with dimethyl bis(hydrogenated tallow) quats had the expected quat content as a function of reduced exchange capacity (approximately 80, 75, and 65 meq/100 g of montmorillonite for the 5, 15, and 30% reduced exchange capacity). 

Increases in shear intensity for the dispersion of montmorillonite into epoxy offer incremental improvements in exfoliated and aligned particle composites. A Lightnin LabMaster SI Mixer was evaluated for the dispersion of Cloisite 30B into EPON 828 [31] and a more effective method, ball milling, was evaluated with montmorillonite exchanged with dodecyl benzyl dimethyl quaternary ammonium ions and meta-xylenediamine [32,33]. 

Low-density polyethylene was utilized as the control (LF-0219-A Novapol). The ethylene-vinyl acetate copolymers varied in vinyl acetate content from 9.3, 18, 28, to 40% (Elvax 760Q, 460, 265, and 40L-03, respectively DuPont). The organomontmorillonites that were evaluated were Cloisite 20A, Cloisite 30B, and montmorillonite exchanged with trimethyl hydrogenated tallow quaternary ammonium ion at the exchange capacity of the montmorillonite. 

The high temperature of the second step precludes the utilization of montmorillonite exchanged with the quaternary ammonium ions described in the work above. These quats are not stable at these temperatures. 

The unstained TEM was the most insightful. The organomontmoril-lonite selection for this work was more limited in relation to the work above. Cloisite 30B, 25A, 20A, and montmorillonite exchanged with benzyl dimethyl hydrogenated tallow quaternary ammonium ion were evaluated. SAN from the above work was the control. The TEM of the unstained ABS indicates the close association of the Cloisite 30B to the interface of the rubber-dispersed phase particles. 

The third article in this series [33] evaluated the exfoliation efficiency of one organomontmorillonite (montmorillonite exchanged at 95 MER with trimethyl octadecyl quaternary ammonium ion) as a function of acrylonitrile content of SAN. Polystyrene was the control (Styron 685 D produced by Dow Chemical with a weight-average molecular weight of 300000 g/mol). The concentrations of acrylonitrile in the polystyrenes were ... 

Heat release rate (HRR) plots for pure EVA EVA with 5wt.% of fluorohectorlte exchanged with amlnododecanoic acid, a microcomposite and EVA with 5 wt.% of montmorillonite exchanged with methyl, tallow, bis-2-dihydroxyethylammonium, a nanocomposite, at a heat flux of 50kW/m. Reprinted with permission from ref. [30]. Copyright (2005) American Chemical Society. 

---