The thesis regards polychloroprene (CR) and ethylene-octene copolymer (EOK) as the matrix material for nanocomposites formed with carbon black nanoparticles (CB) as the electroconductive filler, and characterizes their electrical properties depending on the applied voltage and the temperature reached, in order to obtain flexible, energy-efficient heating elements which are in direct contact and heating the human body directly. The review of literature is about conductivity mechanisms for polymer composites which consider the influence of temperature or voltage, possible natures of the temperature coefficient of resistivity. As well as summarizes the currently very limited number of studies in the field of CR and EOK composites and their resistance dependence on temperature and/or applied voltage. The dependence of electrical resistance on the temperature is determined by heating the composite externally or internally with an applied voltage. The influence of cross-linking the structure of EOK on the thermo-electrical stability of the composite and the nature of the temperature coefficient of resistivity was evaluated. The electrical resistance dependence on temperature is determined in a wide range of CB concentrations for CR and EOK matrix polymer composites. For both types of composite materials, the influence of applied voltage on the electrical resistance and temperature is determined and as a result of the processes taking place in the composite, the most viable electrical conductivity mechanisms have been justified. The effect of polar and non-polar matrix on the electrical conductivity mechanism of the composite was evaluated. The images obtained with atomic force microscope in the electroconductive mode (EC AFM) are analysed and indexes for particle dispersion degree characterization are calculated. The index calculations have been improved, considering the current strength distribution of the formed channels. Practical application aspects for the manufacturing and product properties are discussed and the best combinations for polymer composites composition, electrode material and design for specific applications for example heating elements, are considered. The doctoral thesis is written in Latvian, it consists of 103 pages and it contains 59 figures, 9 tables, 14 formulas and 101 reference.