Dependence of current conductivity of polyethylene-graphite compositions on the method of their manufacture

Abstract

The paper presents the results of the study of the dependence of the properties of polymer composites of the linear high-pressure polyethylene (LHPPET) system – graphite fillers of various types: natural GAK-2, thermally expanded (TEG) and with ultrasonic treatment. The test samples contained a filler in a wide concentration range (5–35 wt. %). Samples were manufactured using rolling, pressing and powder technology methods. Electrical resistance was measured by the four-probe potentiometric method at constant current. It is shown that the electrical resistance decreases sharply in a narrow concentration interval of 5–15 wt. % from 6.77·1010 to 4.9·102 Ω·m (for compositions obtained by rolling), from 2.96·1010 to 1.2 Ω·m (for pressed samples), from 2.87·109 to 0.14 Ω·m (for compositions obtained by powder technology). For samples of the LHPPET – GAK-2 system, a rapid decrease in electrical resistance is observed at filler concentrations of 5–30 wt. % from 1.36·1012 Ω·m to 2.79·102 Ω·m. Using thermally expanded graphite with and without ultrasonic treatment (and to a lesser extent GAK-2) it is possible to obtain polymer composite materials (PCM) with volume resistivity ranging from 6.77 to 1.9·10-3 Ω·m. It has been experimentally confirmed that electrical conductivity largely depends on the PCM manufacturing technology. The established dependences of the current conductivity of composites, depending on the manufacturing method, are associated with the corresponding structural differences. These structural differences are manifested in an increase in the number and area of contacts of filler particles – graphite and in a change in the thickness of the layers of the polymer matrix. Dry powder technology is the most effective method of obtaining LHPPET – graphite compositions. The optimal composition of the composition is 25 wt. % TEG and 75 wt. % LHPPET. Directions of practical use of the obtained results can be effectively used in industry and housing and communal economy.