Study On Solubility And Diffusion Behavior Of Supercritical CO₂ In Polyurethane Systems By Molecular Dynamics Simulation

The solubility and diffusion behaviors of supercritical carbon dioxide?scCO₂?in polyurethane system are important to polymer processing and material performance.Therefore,the solubility and diffusion properties of C0₂ in a series of polyol and polyurethane?PU?reaction product were simulated at pressure from 10 to 40 MPa and temperature range of 318 to 348 K using molecular dynamics simulation.Firstly,the effects of physical parameters and operating conditions on the compatibility between polyol and CO₂,and diffusion property of CO₂ were investigated.It was found that the system compatibility was improved with the increase of pressure and PO?propylene oxide?units,and the decrease of temperature and molecular weight?the trend for low molecular weight polyol was opposite?.In addition,modification of end-group was beneficial to increasing system compatibility.Moreover,the diffusion coefficient increased with the increase of temperature and decreased with the increase of PO units and pressure.However,end group modification reduced diffusion coefficient.By comparing the simulation results with the experimental data,it was verified that polymer-CO₂ interaction played the dominant role in the compatibility,which was further applied to the analysis of PU reaction product system.This article also investigated the effect of polyol functionality,end group,the degree of reaction,temperature and pressure on compatibility between PU reaction products and CO₂,and diffusion behavior of CO₂ in the PU reaction products.The results showed that the compatibility between CO₂ and PU reaction products increased with the increase of pressure and functionality of polyol,while decreased with the increase of temperature and degree of reaction.The diffusion coefficient increased with the rise of temperature,while decreased with the increase of pressure and the degree of reaction.Additionally,end-group modification of polyol had no beneficial influence on both the compatibility between CO₂ and PU reaction products,and the diffusion coefficient of CO₂.The results can bring insights into the formula selection and parameter optimization for CO₂ assisted polyurethane foaming process.