New insights into resins behavior: Influence of resin softening point on in-rubber properties of carbon black-filled SBR compounds

Recent EU regulations have increased the demand for tire materials with improved performance and sustainability. In response, new hydrocarbon resins have been developed to optimize the balance between wet grip, rolling resistance, and wear resistance in tire tread compounds. One of the most important characteristics of resins is their softening point (SP). The softening point of resins plays a critical role in rubber performance due to their influence on the processability and compatibility with other materials. This study investigates the influence of five hydrocarbon resins with the same chemical base but different softening point (ranging from 10 to 160 °C), on the properties of a carbon black-filled styrene butadiene rubber (SBR) compound. The increase in the SP of the resins resulted in higher Mooney viscosity, hardness, tensile strength and Payne effect, indicating a transition from plasticizing to reinforcing behavior. The results also revealed a strong temperature dependence: when the testing temperature exceeded the SP, the resins transitioned to a softened or liquid state, improving dispersion and mechanical performance. Overall, the SP and operating temperature are shown to be key design parameters for tailoring rubber compound properties to specific tire applications. • Effect of the softening point of resins in the in-rubber properties. • Substitution of traditional plasticizers by resins. • Effect of temperature on in-rubber properties of compounds containing resins with different softening point. • New insights of the effect of resins in the dispersion of carbon black.