Study of the Microscopic Mechanism of Natural Rubber (Cis-1, 4-Polyisoprene, NR)/Polyethylene (PE) Modified Asphalt from the Perspective of Simulation

Abstract

This paper aims to study the interaction mechanism of waste tire/plastic modified asphalt from the microscopic perspective of molecules. Based on BIOVIA Materials Studio, a classic four-component asphalt model consisting of asphaltene (C149H177N3O2S2), resin (C59H85NOS), aromatic (C46H50S), and saturate (C22H46) was constructed. Waste tires are represented by natural rubber (NR), which uses cis-1, 4-polyisoprene as a repeating unit. In contrast, waste plastics are characterized by polyethylene (PE), whose optimum degree of polymerization is determined by the difference in solubility parameters. Then, the above molecular models are changed to a stable equilibrium state through the molecular dynamics process. Finally, the interaction process is analyzed and inferred using the indexes of radial distribution function, diffusion coefficient, and concentration distribution; further, the interaction mechanism is revealed. The results show that the optimal degree of polymerization of PE is 12, so the solubility parameter between PE and NR-modified asphalt is the lowest at 0.14 (J/cm3) 1/2. These models are in agreement with the characteristics of amorphous materials with the structures ordered in the short-range and long-range disordered. For NR-modified asphalt, the saturate moves fastest, and its diffusion coefficient reaches 0.0201, followed by that of the aromatic (0.0039). However, the molecule of NR ranks the slowest in the NR-modified asphalt. After the addition of PE, the diffusion coefficient of resin increased most significantly from 0.0020 to 0.0127. NR, PE, and asphaltene have a particular attraction with the lightweight components, thus changing to a more stable spatial structure. Therefore, using NR and PE-modified asphalt can change the interaction between asphalt molecules to form a more stable system. This method not only reduces the large waste disposal task but also provides a reference for the application of polymer materials in modified asphalt.

Microscopic Properties of Asphalt and Polyethylene at an Extraordinary High Dosage through Molecular Dynamics Simulation

“…However, the diffusion coefficient of polar molecules is decreased by about 2% in modified asphalt systems with the addition of 5.8% PE. Yu et al [41] utilized cohesive energy density (CED) as a crucial indicator to determine the degree of polymerization (DP) of PE molecules in natural rubber-modified asphalt. However, the best DP of PE found was only 12, which poses challenges for industrial applications.…”

Preparation of modified sisal microcrystalline cellulose PHS‐g‐MCC and its application in NR/SiO2 composites

“…MD simulations can provide insightful information on the atomic scale, making it difficult to provide experimental methods 25 . On the other hand, MD refers to the study of microscopic phenomena from a molecular or atomic point of view, so as to predict or explain macroscopic phenomena from a microscopic point of view and we can predict whether a molecule is suitable for improving a particular performance 26,27 . Li et al 28 further discussed the compatibility between an asphalt matrix and a styrene‐butadiene‐styrene (SBS) modifier using MD simulations.…”

“…25 On the other hand, MD refers to the study of microscopic phenomena from a molecular or atomic point of view, so as to predict or explain macroscopic phenomena from a microscopic point of view and we can predict whether a molecule is suitable for improving a particular performance. 26,27 Li et al 28 further discussed the compatibility between an asphalt matrix and a styrene-butadienestyrene (SBS) modifier using MD simulations. The simulation results showed that the interaction between SBS modifier and asphalt matrix improved their compatibility, and the van der Waals potential energy was dominant in the intermolecular potential energy.…”

Modification Mechanism and Technical Performance of Recycled PE-Modified Asphalt

“…Among these types, LDPE has a low density and large molecular spacing due to the areas where the saturated aromatics in the asphalt readily penetrate into the molecular chain [24]. Compared to other types of PE, LDPE can be used to significantly enhance the rheological properties of asphalt while granting it excellent high-temperature performance [25][26][27], the latter of which is important for improving the high-temperature rutting resistance of asphalt pavement [28]. Yan et al [29] showed that LDPE can enhance the high-temperature behavior of rubber-modified asphalt and improve the ability of asphalt to resist rutting.…”