Study on the Effect of Lanthanum Stearate on the Compatibility of Desulfurized Rubber with Bitumen Based on Molecular Dynamics Simulation

Compatibility between bitumen and desulfurized rubber (DR) is the most challenging issue affecting the performance of DR-modified bitumen. The aim of this study was to investigate the effects of temperature, DR dosage, and lanthanum stearate (third component) dosage on the compatibility of DR with bitumen by molecular dynamics (MD) simulations. In this paper, the physical properties of DR–lanthanum stearate composite-modified bitumen were firstly tested, and the effects of temperature, DR dosage, and lanthanum stearate dosage on the compatibility of bitumen with DR were analyzed. Molecular models of matrix bitumen, DR molecules, and composite-modified bitumen were then constructed in Materials Studio (MS) software. The effects of temperature, DR dosage, and lanthanum stearate dosage on the compatibility of DR with bitumen were analyzed by calculating the solubility parameter (δ), the interaction energy, and the mean square displacement (MSD) based on a rational model. Finally, the simulation results were compared with those of scanning electron microscopy (SEM). The simulation results showed that the optimal compatibility between DR and bitumen was achieved when the temperature was 135°C, the DR dosage was 30%, and the lanthanum stearate dosage was 1.5%, when the difference in the solubility parameters between DR and bitumen was the smallest, and the interaction energy between them was the largest. Also, lanthanum stearate had a significant effect on the MSD of each bitumen fraction. All these changes in the bitumen molecule indicate that lanthanum stearate plays an active role in improving the compatibility of DR with bitumen. The simulation results are consistent with the experimental results.