Further Understanding\nof Phytic Acid–Based\nDeep Eutectic Solvents as Flame Retardants: COSMO Simulation, Physical\nCharacterization, and Vertical Flame Testing

In this study, deep eutectic solvents\n(DESs) were synthesized\nby\nutilizing choline chloride, ethylene glycol, and glycerol as hydrogen\nbond acceptors (HBAs) and phytic acid as a hydrogen bond donor (HBD)\nat various molar ratios (i.e., 1:1, 1:2, 1:5, 1:10, 2:1, 3:1) to explore\nthe effect of the HBA and HBD content on the thermal stability and\nflame-retardancy capability of the solvents. The sigma surface, sigma\nprofile, and chemical bonding of PA-based DESs were studied utilizing\na Conductor-like Screening MOdel for Real Solvents (COSMO-RS). By\nanalyzing sigma surfaces and sigma potentials, it was observed that\nthe DES components are mainly composed of nonpolar sites, with smaller\npeaks in hydrogen bond donating and accepting sites. Overall, DESs\nexhibit density ranging from 1260 to 1400 kg/m<sup>3</sup>, viscosity\nranging from 0.12 to 0.17 Pa·s, and higher thermal stability\nshown by the increase in the decomposition temperature of the solvents\ncompared to their pure constituents. Finally, cotton fabrics were\ncoated with DESs utilizing a dip coating method, and vertical flame\ntesting was performed. The DES-coated fabrics exhibited self-extinguishing\nproperties, with the best performing DES being ChCl:PA (1:5), taking\napproximately 35 ± 4 s to undergo complete burn, emitting minimal\nsmoke, and creating a char layer on the surface of the fabric. Finally,\nVirtual models for property Evaluation of chemicals within a Global\nArchitecture (VEGA) analysis was conducted on the DES components and\ncommercial flame-retardant chemicals to assess human and environmental\ntoxicity end points, including mutagenicity, carcinogenicity, acute\ntoxicity, and bioconcentration factor (BCF). The findings indicate\nthat these DESs demonstrate minimal toxicity and negligible environmental\nrisks, serving as highly effective and nontoxic flame-retardant applications.