Fine tuning of the dynamic mechanical properties of natural rubber/carbon nanotube nanocomposites by organically modified montmorillonite: A first step in obtaining high-performance damping material suitable for seismic application

•A hybrid filler consisted of two types of nanofillers is used to obtain high-performance damping rubber•Pre-dispersion of carbon nanotubes in ethanol and the high viscosity of the rubber, sufficient for a good dispersion•OMt makes the fine tuning of the dynamic mechanical properties of natural rubber/carbon nanotubes nanocomposites possible

Hybrid natural rubber (NR) nanocomposites, containing 2 phr multiwalled carbon nanotubes (MWCNT) and different quantities (from 0 to 20 phr) of expanded organically modified montmorillonite (EOMt), were prepared in order to produce a NR based material with superior mechanical properties as a first step in obtaining a high-performance damping material suitable for seismic application. Initially a master batch of NR/MWCNT was prepared and then a dilution technique was used for the preparation of NR/EOMt/MWCNT nanocomposites. Raman spectra showed a strong interaction between the rubber matrix and MWCNT and the existence of an only physical mixture of the MWCNT and EOMt. This was reflected on the mechanical properties (both quasi-static and dynamic) which were found to change in the desired way. A remarkable improvement of the lower tensile modulus, tensile strength and storage modulus was achieved with the addition of MWCNT and then a gradual but permanent improvement of the above mentioned properties including improved elasticity and elongation at break with the addition of EOMt. DMA strain sweep measurements showed a pronounced non-linear dependence and a significant increase of the loss factor tan δ (a measure of the dissipation energy) for the nanocomposites with filler concentrations above the mechanical percolation threshold (16 phr).