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Four kinds of polyaniline (PANI)-coated glass fibers (GF-PANI) combined with bulk PANI particles were synthesized. GF-PANI fillers containing different PANI contents were incorporated into an epoxy-anhydride system. The best conductivity behavior of the epoxy/GF-PANI composites was obtained with a GF-PANI filler containing 80% PANI. Such a composite shows the lowest percolation threshold at about 20% GF-PANI or 16% PANI (glass fiber-free basis). The PANI-coated glass fibers act as conductive bridges, interconnecting PANI particles in the epoxy matrix, thus contributing to the improvement of the conductivity of the composite and the lower percolation threshold, compared with that of a epoxy/PANI-powder composite. Particularly, the presence of glass fibers significantly improves the mechanical properties, for example, the modulus and strength of the conductive epoxy composites.

This paper is an extension of previous work on polymerization of anilinium±DBSA (dodecylbenzenesulfonic acid) in an aqueous dispersion in the presence of mica or talc silicate particles. The presence of mica or talc particles greatly accelerates the polymerization process of anilinium-DBSA and an encapsulated structure is formed as well. The catalytic effect of various metallic cations which exist in the chemical compositions of mica or talc on the polymerization kinetics of anilinium-DBSA was investigated. The conductivity results along with microscopy observations prove a well formed encapsulated structure for the polyaniline/mica composites, but less for the polyaniline/talc composites. The anilinium-DBSA complex and mica aqueous dispersions pretreated at different temperatures prior to polymerization have shown a significant effect on the polymerization rate of anilinium-DBSA. The higher the dispersion temperature, the higher is the polymerization rate found.

Conductive adhesives, based on highly filled silver particles dispersed in a liquid epoxy resin, with an aliphatic m i n e [diethyltriamine (DETA)] as a curing agent, were investigated. A third component was added to the epoxy/& system to obtain composites of better conductivity, or similar conductivity but at lower silver contents, to modify the conductive adhesive properties, and also to reduce cost. Epoxy/Ag/carbon black (CB), epoxy/&/carbon fibrils (CF), epoxy/Ag/SiO, and epoxy/Ag/dispersant composites were thus studied. The effect of high curing temperature on the uniformity and resulting conductivity level was also studied. The studied systems, excluding the epoxy/Ag/CB composite, exhibited enhanced conductivities. The microstructure of most of the systems was studied by scanning electron microscopy (SEM). The micrographs produced have served to establish structure-property relations for better understanding of the observed phenomena.

ABSTRACT:Following the previous studies of epoxy/silver conductive composites, a detailed investigation of the influence of ethylene glycol on the resulting resistivity of various composites was carried out. Ethylene glycol was found to have a catalytic effect on the curing process of the epoxy resin, verified by differential scanning calorimetry studies. The accelerated curing process diminishes settling of the metal particles and therefore results in better and more uniform conductivities. High temperature curing of the composites was found to have a similar effect on the conductivity. The conductivity behavior of some other composites, such as epoxy/nickel, epoxy/nickel/carbon fibrils, and epoxy/carbon black/carbon fibrils, were also studied. The structure-property relations were better understood through scanning electron microscopy observations. Silver and nickel particles were found to perform differently in the cured epoxy, showing different percolation concentrations and conductivity levels.

The penetration characteristics of tungsten fiber reinforced metallic glass matrix composite with different tungsten fiber spacing were simulated by LS-DYNA programme. It is indicated that J-C constitutive model for describing deformation behaviour of tungsten fiber can accurately reflect the penetration process of the composite. The simulation results show that the composite has obvious self-sharpening behaviour, and its penetration performance is higher than tungsten alloy. The higher penetration performance depends on close-packing of tungsten fibers separated by metallic glass.