Abstract
This paper reports a comprehensive laboratory study into the thermophysical, physical-mechanical characteristics, and tribological properties of the designed composite materials based on polytetrafluoroethylene. In the structures of machines and mechanisms, a significant role belongs to the tribological conjugations made from polymeric and polymer-composite materials. The reliability of machines, in general, depends to a large extent on the reliability of movable connections. Composite materials of nonmetallic origin have a low cost, they are resistant to most aggressive chemicals and are capable of operating under conditions without lubrication. It was established that the characteristics and properties of materials must be adapted to the working conditions of separately considered tribological conjugations. The mechanisms of thermal destruction have been established, both in the basic material and the carbon fiber based on it. It was found that carbon fiber, regardless of its content (quantity) in the polymer-composite material based on polytetrafluoroethylene, is mainly oriented perpendicular to the force application plane. It was found that with an increase in the carbon fiber content from 10 to 40 % by weight, the heat capacity decreases by 16‒39 % compared to the main material. The optimal operating modes for the designed composite materials have been substantiated on the basis of a pv factor: under a dry friction mode – up to 4 MPa∙m/s; at friction with lubrication – up to 36.4 MPa∙m/s. The dependence has been established of the friction coefficient on the operating modes of a composite material based on polytetrafluoroethylene containing 20 % by weight of carbon fiber when lubricated with oil and water. The results reported here make it possible to synthesize the physical-mechanical characteristics and tribological properties of composite materials in accordance with the required modes of tribological conjugation.
Highlights
The reliability of machines and mechanisms largely depends on the reliability of movable connections
It was established that when carbon fibers are introduced into PTFE in the amount of 10 and 20 % by weight, they are distributed evenly in the polymer-composite materials (PCMs)
A further increase in the concentration of the filler (30 and 40 % by weight) leads to the PCM delamination. This is explained by the local clusters of carbon fibers (CFs) and an insufficient amount of the binder, which prevents the formation of a monolithic PCM when it is heated
Summary
The reliability of machines and mechanisms largely depends on the reliability of movable connections. In their structures, roll or slide bearings are used as rotating elements, equipped, if necessary, with sealing elements. There are technologies for creating PCMs based on PTFE, which can significantly improve its characteristics but the cost of such materials usually exceeds the economic effect of their introduction. The study of the characteristics and properties of the new PCMs is the basis for designing materials with programmed properties, which opens the way to the improvement of the structures of tribological conjugations in machines and mechanisms
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