Investigation of the electrical properties of polypropylene - talc composite

Abstract

Polypropylene-Talc composites with different PP-Talc compositions such as 9:1, 8:2, 7:3, 6:4 and 5:5 were prepared by extrusion moulding method. The X-ray diffractometry(XRD), Infrared (IR) spectroscopy, Thermogravimetric analysis (TGA), Optical microscopic observations and D.C. electrical measurements were carried out on the PP and five different PP-Talc composites. The XRD patterns of the composites shows the peak intensities decrease with increasing Talc concentration. The TGA results reveal that although the weight loss temperature region remain almost same and the percentage of residue left increases with increasing Talc in the composites. At the high temperature, degradation and evolution of gases occur due to chemical reactions in polymer. The optical microphotographic, XRD and IR analysis reveal that there are definite structural transformations ofPP due to the inclusion of Talc. The current - voltage (I-V) characteristics were recorded in voltage range 0 to l50V d.c. at room temperature. From the I-V characteristics it is evident that composites show Ohmic behaviour within the measurement voltage range. The d.c. electrical measurements were performed in the temperature range 298 to 398K. The activation energies obtained are 0.29-0.40 and 0.22-0.42 eV for unannealed and annealed samples respectively. The activation energy has high values in the high temperature region. The activation energy decreases with increasing Talc concentration. This means that shallower traps are created with high talc content. These observations suggest that the d.c. conductivity may be due to carrier motion by variable range hopping between localised states.