Mingshu Yang

Photo-oxidative degradation of polyethylene/montmorillonite nanocomposite

Abstract Photo-oxidative degradation is critical to polymer materials. It is even the case in polymer/layered silicate nanocomposites. A UV photo-oxidative degradation study on polyethylene/montmorillonite (PE/MMT) nanocomposite was carried out by FT-IR technique. It is indicated that the rate of photo-oxidative degradation of PE/MMT nanocomposite is much faster than that of pure PE. The acceleration of photo-oxidative degradation of PE/MMT nanocomposite is due to the effect of MMT and ammonium ion, in which the effect of ammonium ion is primary. It has been found that the dispersion state (either nano- or micro-) of MMT does not seem conclusive on the acceleration of degradation. Fe 3+ modified MMT can also accelerate the photo-oxidative degradation of PE matrix.

Porous hollow carbon nanotube composite cages

Mechanically robust, hollow carbon nanotube composite spheres that are permeable to large chemical species were prepared by a layer-by-layer assembly and templating technique.

Large-Scale Morphology of Dispersed Layered Silicates

Ultra small angle x-ray scattering is used to probe the morphology of highly dispersed montmorillonite (MMT) in water and polyamide-66. In water the scattered intensity, I(q) shows a q -2 dependence for q > 0.01 A -1 , where q is the magnitude of the scattering vector. This is as expected for a two dimensional sheet-like object. On larger scales (smaller q) mass-fractal character is evident up to the radius-of-gyration of the individual scattering entities. The scattering profile is interpreted using a semi-flexible sheet model in which flat, disk-like entities of radius = 80 A (an areal persistence length) are fractally distributed on large scales with a mass fractal dimension of 2.65. These size scales correspond to a scattering entity comprised of one or a few crumpled sheets. No evidence of inter-particle correlations is found at concentrations below the gel point. In polyamide-66 loaded with organically modified MMT long-range fractal behavior is also observed but with larger fractal dimension.