New Flory‐Huggins interaction parameter between SBR and p‐phenylenediamine antioxidants and the predictive power in molecular structure and rubber formula design

The software package was employed to calculate the three‐dimensional solubility parameters (HSP) of SBR and antioxidants. The HSP values of antioxidants are higher than SBR, meaning that the antioxidants have higher polarity compared with SBR. The solubility measurements of antioxidants in both sulfur and peroxide cured SBR vulcanizates were performed at elevated temperatures from 80 to 130°C. The maximum solubilities (∆S) of antioxidants were correlated with the temperature and also with the new Flory‐Huggins interaction parameters (χN) calculated by the HSP values. The results turn out to be that ∆S increases with increasing temperature as expected and 4020 shows higher ∆S value. Furthermore, ∆S increases with decreasing χN, and by quantitatively mathematical fitting, one functional relationship between ∆S and χN was achieved, regardless of what the crosslinking type of SBR was and what the temperature was involved. Through prediction with χN, one can get that SBR grades with higher styrene content and butadiene/vinyl ratio result in lower χN and accordingly better compatibility with N3100. One of the possible applications of χN is to select suitable SBR and antioxidant structures to design the ever‐increasing SBR‐based green tire tread formula.