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Quality control has demanded methods to quantify the mixing state of nanoparticles imbedded in polymeric materials. Several quantification methods are reviewed based on the analysis of images from electron microscopy. This includes the quadrat-based skewness, nearest neighbor distance, the k-function and Monte Carlo method. A novel method in which the dispersion and distribution are evaluated respectively through aspects of the equivalent radius deviation and the distance between the gravity centers of particles or clusters is proposed. The efficacy of the method suggested is illustrated by the analysis of transmission electron microscopy (TEM) images of untreated and vinyl-silane treated 12.5 wt% nano-silica/XLPE. It is shown that the combined method provides complete information on the state of the composite, and is the most direct and convenient methodology.

The addition of nanoscale metal oxide fillers to polymers has been shown, in many cases, to lead to an improvement in the dielectric breakdown strength and voltage endurance. In this paper, dielectric properties for silica- and alumina-filled polyamideimide (PAI) thin films are reported as a function of particle loading. The dispersion and thermal behavior are quantified. Experiments were also conducted using particulates which were functionalized with Aminopropyltriethoxysilane in order to augment the chemical bonding to the host matrix. The glass transition temperature and decomposition temperature are reported as a function of nanoparticle type and loading. The dielectric strength is provided for both AC and DC voltages. It was found that the enhancement in breakdown strength for a nanocomposite formulation is greater under DC conditions than AC. In addition, alumina filled PAI was found to exhibit greater electrical breakdown strength than silica filled PAI. A discussion of possible reasons is included.