To gain an insight of the chemistry in the alkali-promoted aromatization of oxygen-containing heavily aromatic polymers or biomass; thermal degradations of sodium phenolates with different substituents have been investigated. The -ONa group strongly destabilizes the phenolates. The thermal stability of phenolates is largely in parallel with bond strengths of Ar substituents. De-substituents and the removal of aromatic hydrogens are dominant reactions in the main degradation step. CO is formed only at a very late stage. This degradation pattern is completely different from that of phenol. To account for this distinctive decomposition; a mechanism involving an unprecedented formation of an aromatic carbon radical anion generated from the homolytic cleavage of Ar substituent (or Ar–H) in keto forms has been proposed. The homolytic cleavage of Ar substituent (or Ar–H) is facilitated by the strong electron-donating ability of the oxygen anion. A set of free-radical reactions involved in the alkali-catalyzed aromatization have been established.
To take the advantage of reactivity of five‐membered cyclic phosphorus compounds, 1,2,3‐tri‐phenyl‐1,3,2‐diazaphospholidine‐2‐oxide (TPDPO) was explored as a reactive flame retardant for epoxy resins (EPs). Through model compounds, it has been established that TPDPO selectively reacts with the secondary hydroxyl group and is inert toward both aryl amino groups and epoxide groups. The result of Soxhlet extraction supports that TPDPO is permanently bonded to the cured EPs. At a loading of only 8 wt % (0.74 wt % phosphorus), TPDPO enables the cured epoxy to achieve a UL‐94 V0 rating. The thermogravimetric analysis–Fourier transform infrared analyses of the gaseous products suggest that the excellent flame retardancy of EP–TPDPO is partly due to the enhanced dehydration process of the epoxy. Also an increased char yield and the formation of a coherent char layer contribute to the good fire performance of EP–TPDPO. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47411.
An extremely efficient flame retardant with low water solubility has been developed for bisphenol-A based polycarbonate. Potassium trimethylsilylbenzenesulfonate (KTSS) combining trimethylsilyl and sulfonate groups in its molecule is 7 times less water soluble and 5 times more effective in flame retardancy than potassium benzenesulfonylbenzenesulfonate (KSS), the commercial workhorse for polycarbonate (PC). At a loading of 0.02%, KTSS enables PC to achieve a solid UL-94 V0 rating and a limiting oxygen index (LOI) value of 34.4%, representing an increase of 8.5 units. The extremely high efficiency of KTSS stems from its great migration ability to the burning polymer surface facilitated by trimethylsilyl group, its timely release of active alkaline species that promote the charring process of PC, and the stabilization of char by silicon. In addition to the exceptional flame retardancy, PC/KTSS retains excellent physical properties of PC.
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