A Vanillin-Derived, DOPO-Contained Bisphenol as a Reactive Flame Retardant for High-Performance Epoxy Thermosets

Abstract

Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years. Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin, 9,10-dihydro-9oxa-10-phosphophene-10-oxide (DOPO) and phenol via a facile way. VDP is characterized with 1 H NMR, 31 P NMR, FTIR and Time of Flight Mass Spectrometry, and used as a new reactive flame retardant for bisphenol epoxy thermosets. Thermogravimetry analysis shows that when the VDP loading is only 0.5P% (based on phosphorus content), the residue increases from 14.2% to 21.1% at 750°C in N 2 compare with neat DGEBA. Correspondingly, the limit oxygen index increased to 29.6%, and flame retardancy reaches UL-94 V0 grade. Micro combustion calorimetry (MCC) and cone calorimetry analyses demonstrate that VDP can significantly lower flammability of the epoxy thermoset. With only 0.5P% of VDP, the heat release rate, total heat release rate and smoke production are reduced markedly. At the same time, the mechanical properties of the modified epoxy thermosets are also improved. The impact strength increases by 34% and the flexural strength increased by 23%, with 1.5P% of VDP. In short, VDP not only improves the flame retardancy, but also improves the mechanical properties of the epoxy thermosets. KEYWORDSEpoxy resin; bio-based flame retardant; vanillin; properties of thermosets This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A multi‐element flame retardant for rail transit to improve the flame retardant performance of epoxy resin while reducing smoke density

“…Chemical shifts from 7.34 to 7.56 ppm attributed to the aromatic hydrogen (H b ) in the benzaldehyde structure, 8.08 to 8.31 ppm, 7.86 to 8.04 ppm, and 7.65 to 7.82 ppm correspond to the hydrogen on the chiral carbon linked to DOPO (CH, H c ), the hydrogen on the secondary aromatic amine (NH, H d ) and the hydrogen (H e ) on the benzene ring in 3,5‐diaminobenzoic acid; in addition, 2.65 to 2.98 ppm was attributed to the aromatic hydrogen (H f ) in triphenylsilanol. As can be observed in Figure 2b, two distinct peaks appear at 28 and 32 ppm, which are attributed to the possibility that the chiral carbon linked to the phosphorus atom may make it an isomer, a phenomenon also present in other DOPO derivatives 26–31 . The elemental content of DTBD is shown in Figure S1.…”

“…As can be observed in Figure 2b, two distinct peaks appear at 28 and 32 ppm, which are attributed to the possibility that the chiral carbon linked to the phosphorus atom may make it an isomer, a phenomenon also present in other DOPO derivatives. [26][27][28][29][30][31] The elemental content of DTBD is shown in Figure S1.…”

Bio-based flame retardants containing a biphenyl unit for enhancing mechanical properties and fire safety of epoxy resins

“…Additionally, they serve as a physical barrier, impeding the volatilization of combustible gases and effectively safeguarding the structural integrity of the internal system. 56 At the same time, since the biphenyl is also good for char-forming, the two together lead to the formation of a dense and swollen char layer. Figure 10 depicts the Raman spectra of the remaining carbon.…”