Structure and Properties of Poly(vinyl alcohol)/Na⁺ Montmorillonite Nanocomposites

Abstract

Poly(vinyl alcohol)/sodium montmorillonite nanocomposites of various compositions were created by casting from a polymer/silicate water suspension. The composite structure study revealed a coexistence of exfoliated and intercalated MMT layers, especially for low and moderate silicate loadings. The inorganic layers promote a new crystalline phase different than the one of the respective neat PVA, characterized by higher melting temperature and a different crystal structure. This new crystal phase reflects on the composite materials properties. Namely, the hybrid polymer/silicate systems have mechanical, thermal, and water vapor transmission properties, which are superior to that of the neat polymer and its conventionally filled composites. For example, for a 5 wt % MMT exfoliated composite, the softening temperature increases by 25 °C and the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the water permeability. Furthermore, due to the nanoscale dispersion of filler, the nanocomposites retain their optical clarity.

Contribution of nanoclays to the barrier properties of a model proton exchange membrane for fuel cell application

“…This preliminary observation is a strong incentive to model a situation in which the alumino-silicate would be completely delaminated within a polymer usable as a fuel cell membrane. Poly(vinyl alcohol) (PVOH) is a good candidate for this purpose, because silicate layers are known for good dispersion in this polymer [16,17]. Moreover, doping of PVOH by an inorganic acid, such as hypophosphoric acid [18] and phosphotungstic acid [19] is an easy way to increase the ionic conductivity, which makes it a potential candidate as a fuel cell membrane [20], at least at not exceedingly high temperature, at which the polymer would be soluble in water.…”

Effects of ultrasound time on the properties of methylcellulose-montmorillonite films

“…5), it can be found that the films had an intercalated structure, since the peak angle of MMT decreased from 8.7 (pure MMT) to nearly 2 Å . If MMT structure in the films was exfoliated, we could not see any peak in XRD spectrum [6,34].…”

“…1 showed that increasing time of sonication from 45 to 75 min increased d-spacing from 3.88 to 4.83 nm, while peak angles decreased from 2.64 to 2.12 Å . Therefore, incorporation of MC and glycerol into the d-spacing of MMT layers was increased by increasing time of sonication [6,11,34]. There are some relatively small (sodium) ions in the interlayers of MMT and these ions can be exchanged with onium cations in the polymer (MC)/glycerol.…”

Dynamic response and simulations of nanoparticle-enhanced composites

“…45) In Uce,, the first case refers to isotropic systems whereas latter case describes anisotropic systems. The same equation in combined form can be written as:…”