Molecular Simulations of Vapor–Liquid Equilibrium of Isocyanates

Abstract

The wide range of applications of the isocyanates across multiple industries sparks the interest in the study of their phase behavior. A molecular simulation is a powerful tool that can go beyond experimental investigations relying on a molecular structure of a chemical. The success of a molecular simulation relies on a description of the system, namely, force field, and its parameterization on reproducing properties of interest. In this work, we propose a united-atom force field based on the transferable potentials for phase equilibria (TraPPE) to model the vapor–liquid phase behavior of isocyanates. With Monte Carlo and molecular dynamics simulation methods and the introduced force field, we modeled vapor–liquid equilibrium for a family of linear mono-isocyanates, from methyl isocyanate to hexyl isocyanate, and hexamethylene diisocyanate. Additionally, we performed similar calculations for methyl, ethyl, and butyl isocyanates based on the all-atom GAFF-IC force field available in the literature for modeling isocyanate viscosities. We showed that the developed TraPPE-based force field generally overperformed the GAFF-IC force field and overall showed excellent performance in modeling phase behavior of isocyanates. Based on the simulated vapor pressures for the considered compounds, we estimated the Antoine equation parameters to calculate the vapor pressure in a range of temperatures. The predictions are of particular use in the investigation of thermodynamic properties for those isocyanates lacking experimental vapor pressure data. Results can also be employed in modeling the phase behavior of isocyanate mixtures to investigate their sensing and capturing. Furthermore, from the vapor–liquid equilibrium binodals, we predicted the critical properties of isocyanates which can be used in thermodynamic models based on an equation of state.

The role and mechanism of temporary blocked isocyanate at interface between polyethylene terephthalate high‐strength fibers and activation oil

“…The characteristic peak at 1714 cm −1 is contributed by CO 24,25 . However, the infrared characteristic peak of NCO should appear at 2250–2270 cm −1 but could not be observed, indicating that the isocyanate group was blocked 19,26 . In Figure 5b, three absorption peaks at 1631, 1600, and 1470 cm −1 can be observed in spectrum of activation oil, which are ascribed by stretching vibration of CC in benzene ring skeleton, 27 showing that the activation oil contains benzene ring.…”

“…24,25 However, the infrared characteristic peak of NCO should appear at 2250-2270 cm À1 but could not be observed, indicating that the isocyanate group was blocked. 19,26 In Figure 5b, three absorption peaks at 1631, 1600, and 1470 cm À1 can be observed in spectrum of activation oil, which are ascribed by stretching vibration of C C in benzene ring skeleton, 27 showing that the activation oil contains benzene ring. Characteristic peaks at 1253, 910, and 752 cm À1 are related to epoxy groups, 28 those at 1089 and 1045 cm À1 are related to stretching vibration of C O, and peak at 3440 cm À1 is contributed by OH.…”

Current State and Perspectives of Simulation and Modeling of Aliphatic Isocyanates and Polyisocyanates

“…This information was indeed used to investigate the effect of the intermolecular interaction of polyisocyanates on their viscosity, finding that the presence of NCO-Ring interactions is the main factor behind the viscosity rise in functional molecules [89]. The tremendous impact that a dedicated parametrization has on the predictive power of simulations also emerges from the recent work of Emelianova and Gor [100]. In their study, they reparametrized a TraPPE force field to accurately describe the isocyanate NCO group using ab initio calculations as reference data, and they used it to obtain accurate predictions of the vapor-liquid equilibrium curves of linear isocyanates.…”

“…Coarse-grained (CG) modeling [101,102], in which beads representing groups of at- The tremendous impact that a dedicated parametrization has on the predictive power of simulations also emerges from the recent work of Emelianova and Gor [100]. In their study, they reparametrized a TraPPE force field to accurately describe the isocyanate NCO group using ab initio calculations as reference data, and they used it to obtain accurate predictions of the vapor-liquid equilibrium curves of linear isocyanates.…”

“…While there are united atoms representations exist for the more popular force fields, such as for AMBER [103], they still suffer from the problems caused by a lack of parametrization for isocyanates, as proven in Ref. [100].…”