THE EFFECT OF MECHANOACTIVATED KAOLIN AND MAGNESIUM SPINEL ON THE PROPERTIES OF POLYTETRAFLUOROETHYLENE

S. Laukkanen, S. A. Sleptsova, P.N. Tarasova, V.I. Fedoseeva, A.A. Dyakonov
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Index terms: polytetrafluoroethylene, kaolin, magnesium spinel, wear resistance, mechanical activation
Abstract: This paper presents the results of a study regarding the effects of mechanically activated kaolin and magnesium spinel on the physicomechanical and tribotechnical properties of polytetrafluoroethylene (PTFE). It shows the effectiveness of using mechanical activation when combining layered silicates with PTFE and demonstrates how the addition of mechanically activated fillers in PTFE leads to an increase in the elasticity, elastic modulus, and wear resistance of its composites while maintaining its ultimate tensile strength at the initial polymer level. The increase in these characteristics is a consequence of the high adhesive interaction at the boundary phase. By optimizing the ratios of the fillers, it is shown that the addition of magnesium spinel contributes to a decrease in the friction coefficient of polymer composite materials (PCM). To establish patterns of improvement regarding these characteristics, we studied the structure of kaolin and magnesium spinel before and after mechanical activation using capillary electrophoresis, atomic absorption, and IR spectroscopy. The destruction of the octahedral grids of layered silicate during mechanical activation resulted in an increase in the number of active cations of aluminum and magnesium in the mechanically activated kaolin. It is theorized that the high coordination activity of the aluminum ions in the magnesium spinel and kaolin when combined with the fluorine atoms of PTFE macromolecules and the oxygen atoms on the surface of the mechanically activated layered silicate, increases the interfacial interaction at the PTFE-kaolin interface. This theory is confirmed by the results of SEM. A topographic analysis of the low-temperature fragile chipping of the composites shows that the sample’s destruction occurs along the boundaries of the defective regions of the supramolecular formations, instead of the interphase boundary as is often the case with one filler particle to another. The surface of the supramolecular structure is characterized by the presence of bulging radial formations with no clear outline of boundaries on the surfaces without kaolin plates, confirming the cohesive nature of the breakdown of the composites.

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