Further Understanding of Phytic Acid–Based Deep Eutectic Solvents as Flame Retardants: COSMO Simulation, Physical Characterization, and Vertical Flame Testing

In this study, deep eutectic solvents (DESs) were synthesized by utilizing choline chloride, ethylene glycol, and glycerol as hydrogen bond acceptors (HBAs) and phytic acid as a hydrogen bond donor (HBD) at various molar ratios (i.e., 1:1, 1:2, 1:5, 1:10, 2:1, 3:1) to explore the effect of the HBA and HBD content on the thermal stability and flame-retardancy capability of the solvents. The sigma surface, sigma profile, and chemical bonding of PA-based DESs were studied utilizing a Conductor-like Screening MOdel for Real Solvents (COSMO-RS). By analyzing sigma surfaces and sigma potentials, it was observed that the DES components are mainly composed of nonpolar sites, with smaller peaks in hydrogen bond donating and accepting sites. Overall, DESs exhibit density ranging from 1260 to 1400 kg/m3, viscosity ranging from 0.12 to 0.17 Pa·s, and higher thermal stability shown by the increase in the decomposition temperature of the solvents compared to their pure constituents. Finally, cotton fabrics were coated with DESs utilizing a dip coating method, and vertical flame testing was performed. The DES-coated fabrics exhibited self-extinguishing properties, with the best performing DES being ChCl:PA (1:5), taking approximately 35 ± 4 s to undergo complete burn, emitting minimal smoke, and creating a char layer on the surface of the fabric. Finally, Virtual models for property Evaluation of chemicals within a Global Architecture (VEGA) analysis was conducted on the DES components and commercial flame-retardant chemicals to assess human and environmental toxicity end points, including mutagenicity, carcinogenicity, acute toxicity, and bioconcentration factor (BCF). The findings indicate that these DESs demonstrate minimal toxicity and negligible environmental risks, serving as highly effective and nontoxic flame-retardant applications.