Surface epoxy nanocomposites

Ha, SR, Ryu, SH, Park, S J, Rhee, KY. 2007. Effect of clay surface modification and concentration on the tensile performance of clay/epoxy nanocomposites. Mater Sci Eng A-Struct 44S 264—268. 

Chen, J. -S., Pohks, M. D., Ober, C. K., Zhang, Y., Wiesner, U., and Giannelis, E., Study of the interlayer expansion mechanism and thermal-mechanical properties of surface-initiated epoxy nanocomposites. Polymer, 43, 4895-4904 (2002). 

Ha Ha, S.-R., Rhee, K.-Y., Kim, H.-C., Kim, J.-T. Fracture performance of clay/epoxy nanocomposites with clay surface-modified using 3-aminopropyltriethoxysilane. CoUoids and Surfaces A - Physicochemical and Eng. Aspects 313-314 (2008) 112-115. 

Particle pull-out, which leaves hemispherical holes on the fracture surface, is due to the debonding of nanoparticles. The strong interface between treated Al Oj and matrix in epoxy nanocomposites is debonded during tensile testing. Voids are also formed aroimd both treated and non-treated Al O particles. Plastic void formation is also a toughening mechanism. The voids deform more in APTES-Al O /epoxy nanocomposites than NT-Al Oj/epoxy nanocomposites. 

In poorly bonded NT- Al O /epoxy composites, particles are clearly visible and the crack seems to have propagated aroimd their equator. Ihe fracture surface of nanocomposites consists of hemispherical holes (A), top surface of the debonded particles (B) and particles covered by epoxy matrix (C). The crack may propagate above or below the poles of the particles through the matrix. Interfacial debonding seen in the mirror zone is not seen in the hackle zone for treated alumina-epoxy nanocomposites. Another toughening mechanism noticed in the hackle zone is particle pullout, which is seen in both NT- Al O /epoxy nanocomposites and APTES-Al Oj/epoxy nanocomposites, whereas micro-cracking is noticed only in APTES-Al Oj/epoxy nanocomposites. 

The impact fracture surface of the SiO -epoxy nanocomposites system is shown in Figure 9.42. The fracture surface of neat epoxy shows small crazes and the clear river lines with smooth surface. For nanocomposites,... 

Mittal, V. 2008. Effect of the presence of excess ammonium ions on the clay surface on permeation properties of epoxy nanocomposites. Journal of Materials Science 43 4972-4978. 

As mentioned above that high resolution TGA was used to check the purity of the filler so that no local bilayer of the excess surface modification molecules is present in the filler. The commercially treated fillers, however, are often observed to contain an excess of surface modification molecules [16]. This excess can lead to unwanted interactions with the epoxy prepolymer or can thermally degrade at lower temperatures when composites are subjected to higher temperatures thus, the presence of such excess amount is not required. In order to underline the effect of the excess surface modification molecules on the filler surface on the composite properties, epoxy nanocomposites with a number of commercially pro-... 

Thermosetting nanocomposites exhibit a reduced rate of heat release compared to neat polymer. However, the approach to nanocomposites itself is not sufficient to comply with the actual fire test standards. For this reason, traditional flame retardants are currently used in combination with nanofillers, and researchers are focusing on the individuation of synergistic systems. As an alternative to the most common cationic clays, anionic clays show improved performance in terms of flame retardancy. Epoxy nanocomposites based on anionic clay exhibit unique self-extinguishing behavior in a UL-94 horizontal burning test never observed before in a pure nanocomposite. The formation of a continnous intu-mescent ceramic layer on the surface of a polymer during combustion reduces the heat release rate to a higher extent than do montmorillonite nanocomposites. 

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