Electrically conductive composites with polymeric matrix (CPCs) and carbon based filler are the promising group of synthetic materials combining excellent mechanical properties of nonconductive matrix and electrical properties of conductive filler. These materials find application in many fields of interests such as an electromagnetic interference shielding, electro-optical devices, electrostatic discharge or signal transfer used in aerospace, marine, and automotive industries. Conductivity of CPCs can be positively or negatively influenced by many factors, such as change in external conditions, amount of conductive filler, etc. In this work, the changes of conductivity of CPCs with polypropylene matrix and conductive graphite filler are presented. Polypropylene/graphite (PP/graphite) composite was prepared via blending granulated PP, maleic anhydride grafted PP (MAH-g-PP) and natural graphite (either 65, 70 or 75 wt.%). It is obvious that the conductivity increases with increasing amount of conducting filler. The most conductive sample was thermally treated at 170°C for 1 hour or exposed to UV irradiation for 1 and 24 hours. The macroscopic conductivity disappeared and the changes in local current on the surface were studied using scanning spreading resistance microscopy (SSRM). SSRM shows that after the thermal treatment and UV irradiation the conductive areas disappeared and only residual current on the edge of the graphite particles was detected. Positive as well as the negative changes of conductivity of composites have a great influence on their further application.Keywords: polymer composite, polypropylene, graphite, conductivity, scanning spreading resistance microscopy
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