Recent Advances in Characterization Techniques for the Interface in Carbon Nanotube-Reinforced Polymer Nanocomposites

Table 1

Shift in Raman frequency (2691 cm⁻¹) as a function of the tensile strain applied to an ultrahigh molecular weight polyethylene nanocomposite reinforced with multiwalled carbon nanotubes.

Regime	Tensile strain	Shift	Interpretation
Regime (i): elastic region	0–1%	Clear shift to a lower frequency	Elastic response; tensile loading of multiwalled carbon nanotubes
Regime (ii): viscoelastic and plastic deformation occurs	1–10%	Much less apparent shift to a lower frequency	Slip and stick at the interface
Regime (iii): strain hardening occurs	10–15%	Somewhat more apparent shift to a lower frequency	Multiwalled carbon nanotube knots preventing further stretching of the chain of the polymer; tensile loading of multiwalled carbon nanotubes
Regime (iv): partial failure occurs in the polymer matrix at the microscopic level	Larger than 15%	Shift to a higher frequency	Elastic recovery from local failure occurred in the polymer matrix; compressive loading of multiwalled carbon nanotubes

Four regimes of behavior are available for a shift in Raman frequency when different tensile strains are applied to an ultrahigh molecular weight polyethylene nanocomposite reinforced with multiwalled carbon nanotubes. Interpretation of data is available in reference [143].