Frozen non-equilibrium structure for anisotropically deformed natural rubber with nanomatrix structure observed by 3D FIB-SEM and electron tomography

Effect of frozen non-equilibrium structure for anisotropically deformed natural rubber with the nanomatrix structure on mechanical properties was investigated with respect to morphology analysis through 3D observation. Natural rubber with the nanomatrix structure was prepared by graft copolymerization of styrene onto natural rubber particles in latex stage followed by coagulation of the resulting latex. The morphology was observed by electron tomography and focused ion beam-scanning electron microscopy (FIB-SEM). The nanomatrix structure in isotropic state was precisely analyzed by electron tomography and synchrotron scattering technique. The nanomatrix structure was found to consist of natural rubber particles and polystyrene nanoparticles. The frequency-independent loss tangent at plateau region was attributed to the discontinuous nanomatrix structure. After annealing at 403 K and 7 MPa, the nanomatrix became continuous, which resulted in the increases in stress at strain of one and storage modulus as well as increase in loss tangent.