AbstractAccording to the concept of fire life cycle assessment (LCA), a new type of intumescent flame retardant was designed and synthesized by chemically bonding chitosan, phosphorus pentoxide and melamine. The resultant compound, chitosan ethoxyl melamine phosphate (CEMP), was characterized by FTIR, 1H NMR, 31P NMR, XRD and SEM. The performance of CEMP and organic montmorillonite (OMMT) was evaluated in the substrate of epoxy resin (EP) with limited oxygen index (LOI), UL-94, cone calorimetric test (CCT), TGA and TG-IR. As a result, intumescent flame retardant EP (EP3) containing 30.6% LOI and V-0 rating was prepared by adding 3 wt% OMMT and 15 wt% CEMP. The CCT results indicated that CEMP and OMMT reduced the peak of heat release rate (PHRR) to about one fourth that of pure EP and total heat release (THR), 1/2. Decomposition of EP and EP3 was traced from 100 to 600°C by TG-IR.
According to the requirement of fire life cycle assessment (LCA), chitosan ethoxyl urea phosphate (CEUP), an organic–inorganic intumescent flame retardant (IFR) containing phosphorus, nitrogen, and silicon, was synthesized by the reaction of chitosan, phosphorus pentoxide, and urea. FTIR, 1H NMR, SEM, and XRD were employed to characterize the compounds. As a result, CEUP was successfully prepared with higher thermal stability, favorable to enhance fire resistance. Combined with OMMT, the organic/inorganic IFR was applied as EP flame‐retardant agents. The combustion behavior of EP composite was investigated by LOI, UL‐94, CCT, SEM, TGA, and TG‐IR. It was observed that using 15% CEUP and 3% OMMT (EP3), LOI value reached 34.8% and passed the UL‐94 V‐0 rating, while THR and TSP of EP composite reduced 65 and 72% compared with pure EP. The char residue of EP composite was up to 22.4%. The thermal decomposition mechanism was traced from 100 to 600°C by TG‐IR. It was suggestive that CEUP decomposition commenced at 100°C to create phosphoric acid and sublimation of urea occurred at 300°C. EP3 exhibited a strong thermal stability, namely even at 600°C, the volatile substances were detectable. Dense and expanded carbon layer was confirmed in SEM images.
Herein, we report a protocol for highly efficient hypervalent iodine (III) mediated, group-assisted purification (GAP) method for the regioselectivities and stereoselective aminochlorination of electron-deficient olefins. A series of vicinal chloramines with multifunctionalities were acquired in moderate to excellent yields (45-94%), by merely mixing the GAP auxiliary-anchored substrates with dichloramine T and tosylamide as chlorine/nitrogen sources and iodobenzene diacetate as a catalyst. The vicinal chloramines were obtained without any column chromatographic purification and recrystallization simply by washing the reaction mixture with a minimum amount of common inexpensive solvents and thus avoiding wastage of silica, solvents, time, and labor. The GAP auxiliary is recyclable and reusable. This strategy is easy to handle, cost-effective, greener, sustainable, environmentally benign, and mostly suitable for the syntheses of vicinal haloamines from various electron-deficient alkenes.
Chemical synthesis based on Group-Assisted Purification chemistry (GAP) has been prolifically used as a powerful, greener and ecofriendly tool so far. Herein, we report hypervalent iodine (III) mediated regio- and diastereoselective aminobromination of electron-deficient olefins using group-assisted purification (GAP) method. By simply mixing the GAP auxiliary-anchored substrates with TsNH2–NBS as nitrogen/bromine sources and PhI(OAc)2 as a catalyst, a series of vicinal bromoamines with multifunctionalities were obtained in moderate to excellent yields (53–94%). The vicinal bromoamines were obtained without column chromatography and/or recrystallization simply by washing the crude mixtures with cosolvents and thus avoiding wastage of silica, solvents, time, and labor. The GAP auxiliary is recyclable and reusable.
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