Exfoliated epoxy organoclay nanocomposites

A, 135 A, 126 A, respectively. The carbon length of the ammonium cation appears to have no direct effect on the dispersion and exfoliation of nanoclay in the epoxy resin. It appears that the acidic alkyl amnuHiium ions play a key role for the exfoliation of epoxy organoclay nanocomposite (10). 

Chen, B. Liu, J. Chen, H. Wu, J. Synthesis of disordered and highly exfoliated epoxy/clay nanocomposites using organoclay with catalytic function via acetone-clay slurry method. Chem. Mater. 2004, 16, 4864-4866. 

Reinforcement of the epoxy-clay nanocomposites was also dependent on the clay loading as shown in Fig. 29. Thus for epoxy CH3(CH2)17NH3+-MMT nanocomposite system, the tensile strength and modulus increased nearly linearly with clay loading. More than a tenfold increase in strength and modulus could be realized by the addition of ca. 15 wt % of the exfoliated organoclay. 

Figure 7.7 XRD plots of organoclay (modified with octadecyl ammonium cation), epoxy/DDS/clay (intercalated) and epoxy/DETDA/clay (exfoliated) nanocomposites. Reprinted from D.Ratna, N.R. Manoj, R.K. Singh Raman, R. Varley and G.R Simon, Polymer International, 2003, 52, 9,1403 2003 John...

The model illustrated in Figure 2 summarizes the overall mechanism for formation of epoxy polymer - clay nanocomposites. Upon solvation of the organoclay by the epoxide monomers, the gallery cations reorient from their initial monolayer, lateral bilayer, or inclined paraffin structure to a perpendicular orientation with epoxy molecules inserted between the onium ions. A related reorientation of alkylammonium ions has been observed previously for e-caprolactam intercalated clay intermediates formed in the synthesis of Nylon-6 -exfoliated clay nanocomposites (9). Thus, the ability of the onium ion chains to reorient into a vertical position in order to optimize solvation interactions with the monomer may be a general prerequisite for pre-loading the clay galleries with sufficient monomer to achieve layer exfoliation upon intragallery polymerization. 

Lu JK, Ke YC, Qi ZN, Yi XS (2001) Studies of intercalation and exfoliation behavior of organoclays in epoxy resin. J Poym Sci Part B Polym Phys 39 115-120 Lotti C, Isaac CS, Branciforti MC, Alves RMV, Liberman S, Bretas RES (2008) Rheological, mechanical and transport properties of blown films of high density polyethylene nanocomposites. Eur Polym J 44 1346-1357... 

The reduction in the PHRR observed by Camino et al. in a similar DGEBA-anhydride system is considerably higher. They used methyl tetrahydrophthalic anhydride as the curing agent and 10 wt% organoclays. The resulting nanocomposites had an ordered intercalated-exfoliated structure. A reduction of 68 and 38% in the PHRR compared to neat epoxy was observed in a nanocomposite... 

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