(The) study on the properties and formation of anisotropic phase of nano-structured materials containing layered silicates

Abstract

Various polymer-layered silicate nanocomposites (PLSNs) were prepared by melt-intercalation and solution methods. Morphology, Anisotropic phase behavior and shear-induced orientation behavior of PLSNs were investigated Three types of maleated polypropylene/layered silicate nanocomposites with different dispersion states of layered silicate (deintercalated, intercalated and exfoliated states) are prepared from two kinds of polypropylenes with different molecular weights, organically modified layered silicate and pristine montmorillonite to investigate the effect of the final morphology of the nanocomposite on the rheological and mechanical properties. Maleated polypropylene with high molecular weight intercalates slowly and the other with low molecular weight exfoliates fast into the organophilic layered silicates. The rheological properties such as oscillatory storage modulus, non-terminal behavior and relative viscosities have the close relationship with the dispersion state of layered silicates. The exfoliated nanocomposite shows the largest increase and the deintercalated nanocomposite shows almost no change in relative viscosities as well as mechanical property with the clay content. The exfoliated nanocomposite shows the largest drop in complex viscosity due to shear-alignment of clay layers in the shear flow. Morphology evolution, orientational behavior and anisotropic phase formation of the maleated polyethylene-layered silicate nanocomposites and the maleated polypropylene-layered silicate nanocomposites were investigated. The final morphology of both polymer-silicate nanocomposites evolves via four stages; disordered exfoliation, ordered exfoliation, dual states of intercalation and exfoliation, and intercalation in sequence as the concentration of silicate increases. The morphology evolution of nanocomposites is determined by balancing of interactions between a polymer-silicate and between silicate platelets such as a steric interaction and an attract...