E.R. Kutelia, S.I. Bakhtiyarov
New Mexico Institute of Mining and Technology,
Keywords: carbon nanotube, deformation, friction, nanocomposite, polytetrafluoroethylene, Teflon
Summary:The amplitude-independent (AIIF) and amplitude-dependent (ADIF) internal friction and shear modulus of inelastic/elastic behavior of the Polytetrafluoroethylene (PTFE) and PTFE-based nanocomposite materials filled with different amounts (2.5, 5.0, 7.5 and 10.0 wt.%) of monomodal and bimodal nanopowders (Fe cluster doped carbon nanotubes) have been studied experimentally. The measurements of internal friction Q-1(T, ε) and shear modulus G ~ f 2(T, ε) spectra were conducted in vacuum (10-2 torr) using a relaxometer with the reverse torsion pendulum at frequencies of 0.5 - 5 Hz, deformation amplitudes 10-5-10-3, and the heating rates 2 – 5 ˚C/min, over the temperature range 20-350˚C. The values of deformation critical amplitudes (εc) for micro-plastic deformation beginning were determined in addition to activation energies and frequency factors of β(crystalline) and α(amorphous) relaxation processes depending on the concentration and mode of the filler nanopowder in the newly developed PTFE-based nanocomposite material. It is shown that the bimodal Fe atom cluster-doped CNT filler provides a more significant and complex effect on the PTFE matrix structure (ratio of β- and α- phases) and thermodynamic parameters of β- and α-phases (activation energies), that consequently lead to ~25% additional increase in the critical amplitude of micro-plastic deformation beginning (εc) in the synthesized PTFE-based new nanocomposite material.