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An environmentally friendly flame retardant named PO‐PA was designed to enhance the flame retardancy of epoxy resin (EP). Following the principles of efficiency and simplicity, PO‐PA was synthesized through a one‐pot reaction between phenyl phosphonic acid and p‐phenylenediamine. The chemical structure of PO‐PA was characterized by Fourier‐transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), elemental analysis (EA) and thermogravimetric analysis (TGA). EP containing 10 wt% PO‐PA (EP/10%PO‐PA) passed the UL94 V‐0 rating without dripping. In the cone calorimeter test, the total heat release and total smoke production of EP/10%PO‐PA decreased by 44% and 65%, respectively. TG‐FTIR and Py‐GC/MS were used to investigate the pyrolysis gases of the EP composites and PO‐PA, respectively. Scanning electron microscopy (SEM), FTIR, EA and XPS were utilized to study the char residues. It was proved that PO‐PA notably promoted the formation of smooth protective char layer in the condensed phase and effectively inhibited the oxidation chain reactions through releasing the phosphorus‐containing radicals in gas phase, which was not mentioned in the similar research based on phenyl phosphonic acid. [ABSTRACT FROM AUTHOR]

• A new ionic single-crystal compound was prepared by facile neutralization reaction. • EP/5PP-BMI endows EP with superior heat and smoke suppression ability. • EP/5PP-BMI improves tensile, flexural and impact strength by 28.7 %, 54.3 % and 59.3 %. • PP-BMI enables EP to achieve excellent acid and alkali resistance. Preparation of fire safety and high mechanical strength epoxy resin (EP) has become a hot topic for its valuable applications in construction and other fields. Here, bis-2-aminobenzimidazole-modified phenyl phosphonates (PP-BMI) with symmetric structures were synthesized by a simple chemical modification strategy, and its fine structure and composition have been thoroughly characterized. Due to the multifaceted functions of PP-BMI in both gaseous and condensed phases, EP composite with 5 wt% PP-BMI reached a UL-94 V-0 rating and high LOI of 34.3 %. The excellent fire safety of EP/5PP-BMI was further verified with a significant reduction of 57 %, 52 % and 46 % in peak heat release rate (PHRR), total heat release (THR) and peak CO production (P-COP), respectively, compared to the original EP. The flame retardancy of PP-BMI on EP can be attributed to the dilution of non-combustion gases, free radical trapping and catalytic charring functions. More importantly, PP-BMI can further enhance the mechanical properties of EP, which is closely related to the interaction between PP-BMI and EP matrix. Furthermore, EP/PP-BMI composites have good resistance to acids and alkalis, ensuring long-lasting flame retardancy and mechanical properties. This work provides a new strategy for realizing epoxy composites with high fire safety and excellent mechanical properties in construction and multifaceted areas. [ABSTRACT FROM AUTHOR]

Studies on complexation of uranium with organophosphorous ligands in aquatic systems are important from point of view of mobility of uranium in environment. In the present paper, we report the results of complexation of U(VI) by a model ligand for organophosphorus functionalities in humic substances (HS), that is, phenylphosphonic acid (PPA), using electro analytical techniques. The UO22+ has been found to form 1:1 and 1:2 complexes with mono-protonated PPA (HPhPO3-) and 1:1 complex with non-protonated PPA, (PhPO3)2-, with the latter complex (UO2PhPO3) dominating over the other two species. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the redox behavior of UO2PhPO3 species and to explore the kinetics of its reduction by evaluating heterogeneous electron-transfer kinetic (D, ks and α) parameters. The diffusion coefficient (D) value was found to be 6.76 × 10-5 cm² s-1 and 5.03 × 10-5 cm² s-1 at pH 5 and 3, respectively, with rate constant, ks = 0.304 × 10-3 cm/s. Using the DeFord and Hume formalism the stability constant (log ß) of UO2PhPO3 was calculated to be (6.98 ± 0.12), which is in agreement with the literature data. Electrospray ionization mass spectrometry (ESI-MS) studies corroborated the existence of UO2PhPO3 complex. [ABSTRACT FROM AUTHOR]

The carbon steel electrodes were first treated by immersion in 0.1 M phenyl phosphonic acid (C 6 H 5 P(O)(OH) 2 , PPA) solution during 24 or 72 h, then they were transferred into the corrosion test solution representing interstice pore electrolyte polluted by seawater: (sat. Ca(OH) 2 + 0.5 M NaCl) to evaluate the protective effectiveness of the pre-treatment. The investigation was performed essentially by polarisation curves and electrochemical impedance measurements with rotating disc electrode. Very high protective effect was observed with steel pre-treated during 72 h with stationary electrode. From polarisation and electrochemical impedance spectroscopy experiments, the protective efficiency was found to be in the 90–99% range for 72 h pre-treatment. This protective property remains effective even one month immersion. EDS analysis showed the presence of the phosphorus on the steel surface, probably due to the presence of iron-PPA complex. [ABSTRACT FROM AUTHOR]