Effect of molecular structure of polyacrylonitrile fiber on the interfacial adhesion characteristics of modified asphalt

Polyacrylonitrile (PAN) fiber can significantly improve the road performance of asphalt mixtures. The adhesion properties between PAN and asphalt directly affect the structural strength, water stability, and fatigue resistance of asphalt mixtures. In this study, the unit cell model of PAN and asphalt was constructed based on molecular dynamics (MD) simulation, and the rationality of the model was verified. Then, various PAN/asphalt interface models were established. The effects of PAN molecular structure, asphalt composition, temperature, aging, water and salt erosion on the interfacial adhesion properties were studied. Finally, the reliability of the MD simulation results was verified through contact angle experiment. The results show that as the molecular mass of PAN and the content of the second monomer increase, the interfacial adhesion properties between PAN and asphalt improve. Specifically, the interfacial adhesion property between asphalt and PAN prepared with a ratio of 95 % acrylonitrile (AN) and 5 % methyl acrylate (MA) is the best. The interfacial adhesion properties between heavy components in asphalt and PAN are better than that of light components. Higher temperature leads to an increase in the interfacial energy of PAN/asphalt. The interfacial adhesion properties between aged asphalt and PAN are superior to those of unaged asphalt. The resistance of PAN/asphalt interface to salt erosion is inferior to its resistance to water damage. There is a significant linear relationship between the interface energy and the adhesion work. In this study, the effects of various factors on the adhesion properties of the PAN/asphalt interface were systematically analyzed, and the influence mechanism of the adhesion properties of the PAN/asphalt interface was revealed from the molecular scale. This article would be useful to demonstrate the utility of molecular dynamics simulations in investigating interfacial properties in composite materials and provide the atomistic understanding of the PAN/asphalt interfaces.