Molecular Dynamics Simulation and Analysis of Crystallization System in PVC Tunnel Drain-Pipe at Different Temperatures

Aiming at the problem that carbonate and calcium ions are easy to crystallize and precipitate in the drain-pipes of limestone tunnels and then adsorb on PVC pipes in Western China, a "solid-liquid interface model" for the interaction between PVC materials and ions in aqueous solution is established by using the molecular dynamics simulation software materials studio and the microscopic mechanism of crystallization system in PVC drain-pipes at different temperatures is studied. The results show that the self-diffusion coefficient of water molecules increases with the increase of temperature. In the temperature range of 283-308 k, the self-diffusion coefficient of calcium ion and carbonate decreases first, then increases and decreases again with the increase of temperature. When T = 303 K, the self-diffusion coefficient of both ions reaches the maximum value, which makes it easier to crystallize. With the increase of temperature, the binding energy between ionic solution system and PVC increases at first and then decreases. The research results and methods have important guiding significance for the prevention and control of crystal blockage of limestone tunnel drainage pipe.