Nanocomposites resol

Choi and Chung [16] were the first to prepare phenolic resin/layered sihcate nanocomposites with intercalated or exfoliated nanostructures by melt interaction using linear novolac and examined their mechanical properties and thermal stability. Lee and Giannelis [10] reported a melt interaction method for phenolic resin/clay nanocomposites, too. Although PF resin is a widely used polymer, there are not many research reports on PF resin/montmorillonite nanocomposites, and most of the research investigations have concentrated on linear novolac resins. Up to now, only limited research studies on resole-type phenolic resin/layered silicate nanocomposites have been published [17-19] and there is still no report on the influence of nano-montmorillonite on phenolic resin as wood adhesive. Normally H-montmorillonite (HMMT) has been used as an acid catalyst for the preparation of novolac/layered silicate nanocomposites. Resole resins can be prepared by condensation reaction catalyzed by alkaline NaMMT, just as what HMMT has done for novolac resins. 

The mechanical properties of the C3, C6, and Cl2 nanocomposites were all significantly better than those of the neat phenolic resin, even if a very small amount of the silicate was used. Among the nanocomposites prepared, the organically modified MMT-resol systems showed better mechanical properties than those of the unmodified MMT-resol system. This improvement was attributed to the formation of an end-tethered structure due to the reaction of the carboxylic acid of the organic modifier with the methylol group of the phenolic resin. Thermogravimetric analysis reported by Byun and coworkers showed that the nanocomposite systems had similar thermal stability to that of the neat polymer. 

The work on nanocomposites utilizing novolacs and resols can be considered preliminary and promising. The very subtle differences between novolacs and resols appear to have the potential to contribute to significantly different nanocomposite systems. The distinct separation of the silicate layers may provide the basis for the properties of nanocomposites prepared as novolacs or resols. 

Byun, H.Y. Choi, M.H. Chung, I.J. Synthesis and characterization of resol type phenolic resin/layered silicate nanocomposites. Chem. Mater. 2001, 13, 4221-4226. 

Wang, H. Zhao, T. Yan, Y. Yu, Y. Synthesis of resol-layered silicate nanocomposites by reaction exfoliation with acid-modified montmorillonite. J. Appl. Polym. Sci. 2004, 92, 791-797. 

In the case of a resole phenolic resin, the presence of trisilanolphenyl PGSS markedly increased the thermal stability of the phenolic nanocomposites. The... 

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