Molecular dynamics simulation of water permeation mechanism in polymer grouting material

Abstract

Polyurethane (PU) grouting materials are commonly used in infrastructure trenchless rehabilitation projects and are frequently exposed to water environments. However, the underlying microscopic mechanism of polymer damage caused by water infiltration has not been systematically investigated. In this paper, we employed molecular dynamics (MD) simulation to explore the wetting behavior of water on the PU surface and the permeation behavior of PU under pressure. The results showed that when sufficiently high water pressure is applied, PU deforms and creates voids. Subsequently, water molecules begin to penetrate the interior of the PU. For PU models with thicknesses of 10 Å, 15 Å, and 20 Å, penetration behavior was observed at water pressures of 189 MPa, 256 MPa and 314 MPa, respectively. Moreover, with PU models of identical thickness, the depth of water molecules penetration and the volumetric water content of the PU increased with rising water pressure. Furthermore, it was observed that PU has many small interatomic pores in its free state. Under the influence of water, distribution of these pores deviates from a normal distribution and becomes irregular. These findings provide valuable insights into the microscopic mechanism underlying infiltration damage of PU grouting materials at the molecular level.