Systematic all-round examination of the viscoelastoplastic properties of nanocomposites with increased wear resistance based on polytetrafluoroethylene. Part 1

A description of the technology for manufacturing composites with increased wear resistance based on polytetrafluoroethylene is given. The composites were obtained by introducing mechanically activated layered silicates (kaolinite, serpentine, bentonite) and magnesium spinel as fillers. The main results of the study on wear resistance, structure and chemical composition of friction surface using electronic microscopy and infrared spectroscopy and mechanical test data are presented, including families of tensile-to-failure curves at different strain rates, loading and unloading curves at different rates, and creep and recovery curves for different stress levels obtained in tests of pure PTFE and six PTFE composites particulate-filled with serpentine and magnesium spinel with a mass fraction ranging from 1 to 5%. The first part of the article describes the objectives and system of quasi-static testing programs for polymers and composites for a comprehensive study of their viscoelastoplastic properties (a set of all effects observed in tests), the possibilities of describing them using several physically nonlinear constitutive relations of viscoelastoplasticity (one of which takes into account the mutual influence of structure evolution and the deformation process), and the methodology for analyzing test data and selecting adequate constitutive relations for their modeling. In particular, the signs of physical nonlinearity of material behavior are considered, i.e. indicators of inapplicability of the linear integral Boltzmann-Volterra viscoelasticity relation that can be detected in tests using different loading programs, and methods for outlining the range of linearity of viscoelastic material behavior. The tests for preliminary diagnostics of the type of material behavior are described, if we characterize it by the categories elastic, viscoelastic, viscoplastic, elastic-viscoplastic, and the methodology for selecting an adequate model to describe the behavior of a particular material. In the second part of the article, a primary analysis of the expression of hereditary properties of materials is carried out, in particular, speed sensitivity, the ability to flow under constant stress, creep and recovery after unloading, and the influence of the composition, state and proportion of fillers on them.