MWCNTs for tuning viscoelastic and inelastic properties of elastomeric materials

Nanocomposites based on thermoplastic polyurethane (TPU) reinforced with multiwalled carbon nanotubes (MWCNTs) have been prepared with different concentrations (0.1, 5.0 and 20.0% by volume). The effects of MWCNTs addition into TPU upon viscoelastic and dissipative properties have been investigated at both small and high strains. Dynamic mechanical tests performed at small strains have shown that either storage modulus or loss tangent of the reinforced TPU increase with nanotube content. Cyclic tensile tests have illustrated that at high strains (100-300%) the fraction of dissipated strain energy increases with the amount of MWCNTs (even of one order of magnitude). SEM investigation and SAXS measurements of strained and unstrained TPU samples have provided indications about the dissipative phenomena in the nanocomposite systems. Nanocomposite TPU films were inserted within rigid glassy thermoplastic plates in order to produce a model composite system with an interleaved damping layer. The investigation of dynamic mechanical properties of such system has shown that nanotubes addition into damping layer restrains the flexural properties reduction and, at same time, increases impact (100-167%) and damping properties (69-149%).