Influence of Gel on the Payne Effect and Mullins Effect of Butadiene Rubber

Gel is an unavoidable byproduct of butadiene rubber (BR) polymerization that significantly impacts the Payne and Mullins effect. Unfortunately, the impact mechanism remains unclear. Herein, the compounds of BR and gel (BR/gel) with varying cross-linking densities (vc) are prepared and their rheological and mechanical properties are investigated. In low-cross-linking systems (systems’ vc < gel’s vc), gel amplifies the Payne effect by restricting chain mobility and intensifying dissipation. In high-cross-linking systems (systems’ vc > gel’s vc), gel creates defects and weakens the Payne effect. During cyclic tensile deformation, the gel exhibits increased recovery hysteresis and accumulated softening energy losses, suggesting elevated dissipation due to chain friction and defects, thereby amplifying the Mullins effect. This investigation provides insights on the Payne effect and Mullins effect for BR/gel with increasing vc.