Solid–Liquid Phase Equilibrium of Phosphoramidic acid, N,N′-1,2-Ethanediylbis-P,P,P′,P′-tetraphenyl Ester in Selected Solvents

Abstract

Phosphoramidic acid, N,N′-1,2-ethanediylbis-P,P,P′,P′-tetraphenyl ester (PAETE) was prepared and characterized by elemental analysis (EA), mass spectra (MS), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR). The thermostability of PAETE was measured via thermogravimetric analysis (TGA). The melting temperature and the fusion enthalpy of PAETE were evaluated by differential scanning calorimeter (DSC). The solubilities of PAETE in ten selected solvents were obtained using a gravimetric method. The experimental data were well correlated by the Buchowski−Ksiazczak (λh), Scatchard−Hildebrand, modified Apelblat model, and the ideal equations. The solubility parameter of PAETE was estimated by the Scatchard−Hildebrand Model. The dissolution enthalpy and entropy of PAETE in the ten selected solvents were also calculated by the modified Apelblat model. ■. INTRODUCTIONThe high-level living standard would not be possible without the development of polymeric materials that have appeared since World War II. 1 Nowadays, polymers have been widely used in various fields, such as aerospace, mechanics, and chemistry, due to the good heat endurance and mechanical performance, small chemical corrosion resistance, and so on. 2 Unfortunately, almost all of the polymers are easily to burn, which limits their applications in electronics, transportation, cabling, construction, and so on. Flame retardancy is mandatorily required in the fields mentioned above. 3 To decrease the fire hazards and expand the range of the applications for the polymer materials, it is urgent to develop the flame retardant polymer materials. It is well know that adding the flame retardant additives into the polymer materials is an effective method to enhance the flame retardancy. Recently, some reports indicate that the flame retardant efficiency can be greatly enhanced while nitrogen and phosphorus elements are present together in the polymer systems. The synergism of phosphorus and nitrogen elements has been recognized in many research works. 4−7 Now, it is predicted that the phosphorus−nitrogen-based flame retardants will be the biggest growing share in the flame retardant market. 8 Phosphoramidic acid, N,N′-1,2-ethanediylbis-P,P,P′,P′-tetraphenyl ester (PAETE) (C 26 H 26 N 2 O 6 P 2 , CAS Registry No. 34670-52-5) has gained increasing attention over the past years as a versatile intumescent flame retardant because the phosphorus and nitrogen elements present in the formula. Figure 1 shows the chemical structure. PAETE possesses a bright future because of its powerful flame retardancy. It has been widely used in thermoplastic polyolefin, 9 polyethylene, 10,11 epoxy resins, 12 polycarbonate(PC), 13 and so forth.However, some impurities have greatly effects on its thermal property and the application. Hence, purifying PAETE is important to gain the product with high purity.As the solubility of PAETE in water is very low, knowledge of (solid + liquid) equilibrium of PAETE in organic solvents is especially necessary for determining the optimal con...

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