Viscoelastic Properties and Sulfur Distribution at the Nanoscale in Binary Elastomeric Blends: Toward Phase-Specific Cross-Link Density Estimations

Immiscible blends of elastomers present high technological interest, and the selection of the vulcanization system is important for the optimization of properties for different technical applications. In particular, the effect of the curing agents on the distribution of cross-links in each phase is key for the full comprehension of the structure–property relationships. Aiming at the understanding of the phase-specific network structure in rubber blends, this work presents an innovative strategy for the quantitative characterization of the local viscoelastic properties of immiscible rubber blends by atomic force microscopy (AFM) measurements. A systematic study on the quantitative nanomechanical characterization by AFM of unfilled single natural rubber (NR) matrixes with different degrees of cross-link densities ultimately allows for the estimation of the phase-specific cross-link density of the NR phase in NR/butadiene rubber (BR) blends, prepared with varying vulcanization systems. Complementary chemical information by high-resolution secondary ion mass spectrometry imaging is able to reveal differences in sulfur contents in each elastomeric phase of the blends.