Dispersion state and hyperelastic behavior of tire tread compounds reinforced with nanoclay: Uniaxial tensile and compression studies

Tire-tread compounds based on natural rubber, butadiene rubber, and styrene-butadiene rubber (65/20/15) were reinforced with Cloisite 15A. Clay state-of-dispersion in the ternary matrix (clay aspect ratio and clay/matrix interface yield strength) was estimated using Halpin–Tsai, Guth, and Leidner–Woodhams–Pukanszky micro-mechanical models. The aspect ratio suggested by Halpin–Tsai (9.7) and Guth (16) models both propounded partially intercalated microstructure. Transmission electron microscopy micrographs indicated higher reliability of Halpin–Tsai theory. Wetting parameter values indicated the affinity of Cloisite 15A to disperse in butadiene rubber. However, it seems that clay particles were not provided with proper compounding conditions to further stabilize their thermodynamic state. The poor matrix/clay adhesion was responsible for the decrease in matrix/clay interface strength and thickness upon increasing clay content according to Leidner–Woodhams–Pukanszky. Hyperelastic modeling was conducted using Abaqus software (five strain energy potential forms) on the basis of large deformation uniaxial tension/compression measurements. Effect of nanoclay on the crosslink-density of samples was justified by C₁₀ (Mooney–Rivlin) and locking-stretch (Van der Waals) values. The sample containing 1 phr nanoclay presented the best fit to the hyperelastic models among the rest conforming to its small value of global interaction parameter “a”(Van der Waals model) calculated explaining minimum deviations. Overall, Marlow and Ogden provided the best consistency with the experimental stress–strain results.