Phenolic resins nanocomposites

This entry will provide an overview of the classical phenol-formaldehyde system. The fundamentals of this system will be described. The current applications of this classical system will be discussed. Resins prepared from structurally modified phenols will be examined and labeled as modified-classical phenol-formaldehyde systems. The effect of these modifications on the mechanical, thermal, and other properties will be examined. Finally, the considerable work on polymers that can be classified as nonclassicaf phenolic resins will be presented and the area of nanocomposites utilizing phenolic resins will be examined. 

The aim of this entry is to present a balanced view of the current state of phenolic resins. The patent literature, refereed journals, and other general sources have been utilized to survey the classical and nonclas-sical phenolic resin systems as well as the nanocomposite systems. The article is pedagogical rather than comprehensive. 

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. 

Lee, J.D. Giannelis, E.P. Synthesis and characterization of unsaturated polyester and phenolic resin nanocomposites. Polym. Prepr. Div. Polym. Chem. 1997, 38 (2), 688-689. 

Choi, M.H. In, J. Mechanical and thermal properties of phenolic resin-layered silicate nanocomposites synthesized by melt intercalation. J. Appl. Polym. Sci. 2003, 90 (9), 2316-2321. 

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. 

In another example, tubular ZnO/CoFc204nanocomposites have been prepared via solution growth methods. After dispersion in a phenolic resin, the nanocomposites... 

Thus, to modify compositions with finely dispersed suspensions it is necessary for the latter to be active enough that should be controlled with IR speetroseopy. A number of results of material modification with finely dispersed suspensions of metal/carbon nanocomposites are given, as well as the examples of changes in the properties of modified materials based on concrete compositions, epoxy and phenol resins, polyvinyl chloride, polycarbonate, and current-conducting polymeric materials. 

Yoon etal)- reported the synthesis of mesoporous carbon using as-synthesised MCM-48 silica/surfactant mesophase as the template, followed by introduction of carbon precursor (divinylbenzene), carbonisation and removal of silica. Hyeon and co-workers " reported the synthesis of mesoporous carbon by the carbonisation of composites containing silica, P123 triblock copolymer and phenol resin, followed by removal of silica. The synthesis was achieved by treating the as-synthesised silica/triblock copolymer nanocomposite with sulfuric acid to crosslink the triblock copolymers followed by carbonisation. " Kim et al. reported the synthesis of carbon nanotubes using PI 23 surfactant inside mesoporous silica, although ordered arrays of carbon nanotubes were not observed.Kawashima et al. synthesised mesoporous carbon via copolymerisation of tetraethoxysilane (TEOS) and furfuryl alcohol. 

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. 

Chiang and co-workers [50] studied the flame retardance of phenolic resin-silica nanocomposites. The char yields of the polymer were observed to increase when the tetraethoxysilane content of the polymer was increased. LOI and UL-94 [13] tests revealed that the hybrid possessed excellent flame resistance. 

Polyurethane/clay-based nanocomposites are already being used for automobile seats and it also exhibit superior flame retardancy. Phenolic resin impregnated with montmorillonite clay was already identified as the resin for manufacturing rocket ablative material with MMT. The nanolevel dispersion of clay platelets leads to a uniform char layer that enhances the ablative performance. The formation of this char was slightly influenced by the type of organic modification on the silicate surface of specific interactions between the polymer and the silicate platelets surface, such as... 

Shojaei, A, Faghihi, M. Physico-mechanical properties and thermal stability of thermoset nanocomposites based on styrene-butadiene rubber/phenolic resin blend. Mat. Sci. Eng. A. 527, 917-926 (2010)... 

Schutz et al. studied the thermal properties of a phenolic resin nanocomposite containing silsesquioxanes [80]. The thermal oxidative stability of the nanocomposites was improved, as compared to that of the piu e resin. This effect may be a consequence of the formation of a protective layer of SiG2 during silsesquioxanes pyrolysis at the surface of nanocomposites, which retarded the thermal oxidative degradation. The temperatures characteristic to thermal degradation processes were higher in the case of nanocomposites, compared to the pure resin matrix. 

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

The nanocomposites obtained firom phenolic resin and carboxylated MWNTs showed an improvement of the thermal stability than the neat phenolic resin. The highest thermal stability was obtained in the case of the nanocomposites obtained by in situ polymerization, due to the quality of dispersion of the functionalized MWCNTs [94]. An enhancement of the thermal stability was also obtained in the case of nanocomposites containing boron phenolic resin and MWCNTs modified with nitric acid, 4,4 -diaminodiphenyl methane and boric acid. This effect was ascribed to better interfacial interactions between modified MWCNTs and the resin matrix [95]. 

The effect of carbon nanofibres on the thermal behavior of phenolic resins was studied by Bafekrpour et al. [96]. The presence of carbon nanofibres produced an increase in the thermal stability of the nanocomposites, compared to the neat phenolic resin. Thus, the decomposition temperature was shifted to higher values with an increase of the nanofibres content. The same trend was obtained for the nanocomposites char yield. 

Jiang, W., Chen, S.H., Chen, Y. Nanocomposites from phenolic resin and various organo-modified montmorillonites preparation and thermal stability. J. Appl. Polym. Sci. 102, 5336-5343 (2006)... 

Zhang, Z., Ye, G., Toghiani, H., Pittman Jr, C.U. Morphology and thermal stability of novolac phenolic resin/clay nanocomposites prepared via solution high-shear mixing. Macromol. Mater. Eng. 295, 923-933 (2010)... 

Schutz, M.R., Sattler, K., Deeken, S., Klein, O., Adasch, V., Liebscher, C.H., Glatzel, U., Senker, J., Breu, J. Improvement of thermal and mechanical properties of a phenolic resin nanocomposite by in situ formation of silsesquioxanes from a molecular precursor. J. Appl. Polym. Sci. 117, 2272-2277 (2010)... 

Zhang, Y., Lee, S., Yoonessi, M., Liang, K., Pittman, C.U. Phenolic resin-trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) hybrid nanocomposites structure and properties. Polymer 47, 2984-2996 (2006)... 

Liu et al. [72] used POSS nanomodification in phenolic resin with carbon fiber reinforcement. SEM analysis showed the production of best charred surface on burnt samples that enhanced the ablation performance. Novel flake graphite was introduced into barium-phenolic resin by Yu and Wan [73]. Nanocomposites were made by roller-coating technology and its ablation property was tested under long pulse laser radiation. Nanocomposites showed better ablation performance compared to the control system. It was also observed that the size of the graphite flake affected the ablation rate [73]. Srikanth et al. [74] prepared ablative nanocomposites by introducing nanosilica into the phenolic resin with carbon fiber reinforcement. Ablation resistance of nanocomposites increased with the nanosilica content up to 2 wt%. However, beyond this point ablation resistance decreased. 

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