Polymer, Vol.167, 109-117, 2019
Insight into the weak strain overshoot of carbon black filled natural rubber
Weak strain overshoot (WSO) of loss modulus accompanying with strain softening under large amplitude oscillatory shear deformation is a common phenomenon that occurs in many systems but is still far from being clarified. Study about WSO has a strong practical significance, for it is directly related to sharp increase of energy dissipation of elastomer nanocomposites experiencing dynamic deformation of large strain amplitudes. Herein a systematical investigation was performed on WSO of uncured natural rubber (NR) and its low-loading carbon black compounds and a frequency-temperature-volume fraction diagram for the onset of WSO is firstly proposed to shed light on the mechanisms. A comparison of rheology behaviors of uncured polyisoprene rubber and NR and cured polyisoprene rubber suggests that WSO in NR originates from the non-isoprene fraction. Fourier-transform infrared spectroscopy measurement suggests the dissociation of hydrogen bonding at high temperatures, which accelerates the stress relaxation.