Title : Electrical behaviour of composite materials with polymer matrix / metal powders
Abstract:
The interest for polymer / metal filler composite materials results from the fact that their electrical properties are close to those of metals and the mechanical characteristics and processing methods are close to those of plastics. In such composites there is the possibility of controlling the electrical and physical characteristics which determines a wide variety of their applications. The composites obtained may have a range of excellent properties, high electrical and thermal conductivity, high specific strength and modulus, high temperature resistance, corrosion resistance etc. The article studies the electrical characteristics of composite materials with polypropylene and polyethylene matrix with Fe and Al metal powders. A comparative study of the electrical characteristics for different quantities of metal powders (3, 5, 8%) is made in connection with the dimensions of the metallic particles, the mechanical and thermal characteristics and the morphological changes of the composites. It was proved the existence of the agglomeration of particles from powders prior the preparation of the composite samples. For this reason in the article average values of their dimensions were used. The agglomerations of the particles are persistent and do not decompose in totality during extrusion and injection processing, their number increasing with increasing content of metal powders. Electrical behaviour at different frequencies was investigated at temperatures close to room temperature by Dielectric Spectroscopy. The dependence of losses on the nature of polymers, metal powders, dimensions and the amount of particles was shown. Important data were obtained for materials in which the metal powders have nano dimensions. The results obtained were correlated with changes in mechanical and thermal characteristics. Morphological analyzes of metal powders and composites were determined by DSC and SEM analyzes. Different variations of the crystallinity are observed for the two polymers. Particles with nano dimensions penetrate more easily both in the amorphous domains and in crystalline domains.
