Syntheses and characterization of two novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-based flame retardants for epoxy resin

Abstract

Two novel phosphrous-nitrogen-containing flame retardants (3) and (4) were successfully synthesized from two steps: condensation reaction between 4-aminopenol and 1,4-phthaladehyde (or 4,4 0 -biphenyldicarboxaldehyde) and addition reaction between the above condensation compounds and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The structures of (3) and (4) were characterized by Fourier transform infrared, nuclear magnetic resonance, and mass spectroscopy methods. The results show that (3) and (4) can serve as co-curing agents of diaminodiphenylmethane (DDM) for the curing reaction of epoxy resin. The epoxy thermosets-containing DDM and (3) or (4) exhibit moderate changes in glass transition temperature, thermal stability, and show improvement in flame retardancy: UL94 V-0 grade can be obtained when phosphorus content of the epoxy thermoset is only 1.0%; the limiting oxygen index of epoxy resin system containing (4) reaches 40.9 when phosphorus content is up to 1.5%.

Flame‐retardant performance and mechanism of epoxy thermosets modified with a novel reactive flame retardant containing phosphorus, nitrogen, and sulfur

“…Two secondary amine peaks in the range of 6.39 to 6.50 and 6.25 to 6.38 ppm, and 2 methine peaks at 5.36 and 5.18 ppm confirmed the existence of 2 diastereomers. Similar phenomenon was previously observed . In addition, 2 peaks at 30.86 and 28.39 ppm were observed in the 31 P NMR spectrum of BPD in Figure , which further verified the existence of 2 diastereomers.…”

“…Similar phenomenon was previously observed. 30 In addition, 2 peaks at 30.86 and 28.39 ppm were observed in the 31 P NMR spectrum of BPD in Figure 3, which further verified the existence of 2 diastereomers.…”

Intumescent flame retardancy of a DGEBA epoxy resin based on 5,10-dihydro-phenophosphazine-10-oxide

“…The filtrate was treated with 10% aqueous NaOH to precipitate a yellow substance and then evaporated ethanol to get crude product. After being washed three times with water, the product DPPA was recrystallized from glacial acetic acid and vacuum-dried at 70 °C for 24 h. 1 …”

“…The high flammability, however, limits broader applications of epoxy resins. [1][2][3] It is necessary to prepare the high-performance epoxy resins with non-flammablity for meeting the quality requirements of today's society for epoxy resins. For the possible health and environment hazards associated with the use of halogenated flame retardants, the worldwide interest in halogen-free flame retardants has increased in recent years.…”

The application of organophosphorus flame‐retardants in epoxy resin

“…Phosphorus flame‐retardants have been used to efficiently inhibit and improve the thermal properties of EP, especially for use in the electrical, electronic, and aerospace industries . They include the following: red phosphorus and ammonium polyphosphate (both free and encapsulated), 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and its derivatives , phosphate esters , phosphonate‐melamine compounds , silicon/phosphorus hybrids , phosphonate esters , salts of alkylphosphinic or alkylphosphonic acids , and nanocomposites .…”