Water uptake epoxy nanocomposites

The water absorption behavior of the clay-epoxy nanocomposites in terms of maximum water uptake and diffusion coefficient are given in Table 9.18 [47]. The presence of nanoparticle as reinforcement reduces the water absorption of the composite system. The maximum water uptake of epoxy decreases gradually with the increase in clay content. The maximum water absorption decreases by 14.1,17.9 and 24.8% after the incorporation of 1, 3 and 5 wt% nano-clay, respectively, compared with neat epoxy. The presence of high aspect ratio nanofillers can create a tortuous pathway for water molecules to diffuse and enhances the resistance to water absorption. The diffusivity also decreases in the same manner and a significant reduction in diffusivity is obtained for the composites containing 5 wt% clay [112]. 

Table 9.18 Maximum water uptake and diffusion coefficient (D) of clay-epoxy nanocomposites. Reprinted from [47] with permission from Elsevier.

Liu, W, Hoa, S. and Pugh, M. (2005), Fracture toughness and water uptake of high performance epoxy nanocomposites , Composites Science and Technology, Yol. 66, pp. 2116-2125. 

Becker O, Vailey RJ, Simon GP (2004) Thermal stabiUly and water uptake of high ptaformance epoxy layered silicate nanocomposites. Eur Polym J 40(1) 187—195 Bergaya F, Jaber M, Lambert IF (2012) Qays and clay minerals as layered nanofillers for (bio) polymers. Green En Tech 50 41—75... 

Previous work by Sancaktar and Kuznicld (2006) also showed reduction in water uptake in nanoclay/epoxy composites, specifically when stressed to stagger the clay layers with the action of strain that squeezed the layers to a smaller interlayer distance, thus producing a more effective barrier against water diffusion into the nanocomposite adhesive. This trend was not observed in the unfilled epoxy system, in which barrier properties were not affected by stressing below the yield point. 

Sancaktar E, Kuznidd J (2006) Stress-induced reduction of water uptake in clay-reinfor< d epoxy nanocomposites. Curr Nanosci 2 351—357... 

A study by Shah et on die moisture diffusion of a (non-epoxy) vinyl ester resin-based layered silicate nanocomposite also reported a deereased moisture diffiisivity of the nanocomposite, ascribed to the restricted mobility of the polymer chains tethered to the clay particles. A reverse effect, however, could be observed for the equilibrium water uptake of one of the two fillers investigated. The equilibrium water uptake of a vinyl-monomer containing clay nanocomposites increased from 0.012% (neat resin) to 0.021 (5% clay). The water uptake of the other, an alkyl ammonium-treated montmorillonite clay, Cloisite lOA, remained relatively unaffected by the filler addition. The increase of the first nanocomposites system was related to the strong, hydrophilic behaviour of the clay, which remains to some degree in the surface treated state. 

Becker et al investigated the water uptake of a series of highly crosslinked (high performance) epoxy nanocomposites containing 0-10% of a commercially... 

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