Preparation and Characterization of Carbon Black Filled Polypropylene/Polyamide 6/Glass Fiber Composites

Carbon black (CB) filled polypropylene (PP) with surface resistivity of 10⁶-10⁹ Ω is the ideal antistatic plastic material in electron-electric industry. However, the large amount of CB may have adverse effect on the mechanical properties and processing performance of the material. CB and glass fiber (GF) were added to the mixture of PP and polyamide 6 (PA6) through melt-blending process to fabricate a conductive composite with low electrical percolation threshold. The influence of the mass fraction of fillers towards thermal stability, electrical conductivity, mechanical properties and morphology were investigated. SEM results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. Meanwhile, the surface of GF was covered with PA6, and the GF with high aspect ratio formed a continuous structure by interconnections, which greatly decreased the percolation threshold of the composite. Under the same mass fraction of CB (2%), the surface resistivity of PP/PA6/GF/CB decreased by 5 orders of magnitude compared with PP/PA6/CB. In the PP/PA6/GF (mass fraction:80/10/10) system, the thermal stability of the composites were improved because of the introduction of inorganic particles. Besides, GF formed a network structure inside the matrix, which hindered the movement of PP and PA6 molecular chains and lowered the crystallization temperature. The dielectric constant, dielectric loss, and AC conductivity all showed an upward trend as the mass fraction of CB increased, and percolation occurred near 2%-3% (mass fraction). With the increase of CB and GF mass fraction, the tensile strength of PP/PA6/GF/CB system gradually increased, and the elongation at break remained basically unchanged.