The reactive process can be used to controll the dispersion of montmorillonite (MMT) in ethylene vinyl acetate (EVA). MMT/EVA partial nanocomposites (partially dispersed MMT) and nanocomposites (completely dispersed MMT) have been prepared using a conventional twin screw extruder. Our results show that the partial nanocomposites have a better balance of mechanical properties and flame retardance than complete nanocomposites.

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Polymeric materials filled with dispersed electrically conductive fillers are used as functional materials in various industrial fields. Some of these composite materials show positive temperature coefficient resistivity (PTC) i. e., the resistivity of the material increases with an increase of temperature. By applying this PTC effect, these electrically conductive materials are able to be used as self-temperature controlled plane heaters. In this study, high-density polyethylenes (PE) filled with short nickel-coated carbon fibers (NiCF) were prepared by calender molding and compression molding. The influence of various factors such as fiber content, fiber orientation, temperature, processing method and expansion coefficient of the matrix polymer on the electrical conductivity of the composites were investigated experimentally. Heating behaviors of these materials were also characterized by surface temperature measurements. It was found that volume resistivity decreases exponentially with an increase in fiber content, and gradually levels off at further increases in fiber content. The relationships between fiber orientation and volume resistivity and also between temperature dependent resistivity and expansion of matrix polymer are shown to have good correlations. Heating behaviors of these materials are influenced strongly by fiber orientation. The composites investigated in this study show the PTC effect both with a change in environmental temperature and also heating under supplied voltage.

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