INFLUENCE OF SERPENTINE AND MAGNESIUM SPINEL ON PHYSICO-MECHANICAL AND TRIBOTECHNICAL PROPER-TIES OF POLYTETRAFLUOROETHYLENE

XUIRLG

Abstract

The effect of hybrid filling (mechanically activated layered silicate – serpentine and nanosized synthetic magnesium spinel on the physico-mechanical, tribotechnical properties and structure of polytetrafluoroethylene (PTFE) was examined in this thesis. The deformation-strength characteristics of polymer composites (tensile strength, relative elongation, modulus of elasticity) and tribotechnical parameters (mass wear rate, friction coefficient) were determined. It was established that the physico-mechanical parameters depend on the concentration of hybrid filler. It was shown that the optimal concentration of the hybrid filler is a small filling: the content of serpentine (up to 2 wt.%) and magnesium spinel (up to 0.5 wt.%), leading to the maximum increase in the wear resistance of the composite, while maintaining the deformation-strength characteristics. At the same time, an increase in relative elongation at break up to 23% was registered, while maintaining the values of tensile strength and elasticity modulus at the level of the initial polymer. Meanwhile, the coefficient of friction is approximately 0.24, the rate of mass wear is reduced to 1100 times relative to the initial polymer. The supramolecular structure of polymer composite materials in the bulk of the material and friction surfaces were studied using scanning electron microscopy (SEM) to explain such a change in the properties of the composite.  It has been established that the lamellar supramolecular structure of PTFE is transformed into a spherulite structure upon the addition of serpentine, the dimensions of which decrease with the additional introduction of nanosized magnesium spinel. When studying the morphology of the friction surface of composites it was found that filler particles accumulate on the friction surface during wear and form a secondary structure that localizes shear deformations and protects the material from destruction.