Synthesis of phosphorus and silicon co‐doped graphitic carbon nitride and its combination with ammonium polyphosphate to enhance the flame retardancy of epoxy resin

Abstract

Phosphorus and silicon co-doped graphitic carbon nitride (PSiCN) was synthesized by inducing the polycondensation reaction of melamine, diammonium hydrogen phosphate, and silicic acid. The structure and thermal properties of PSiCN were characterized. With the incorporation of 2 wt% of PSiCN and 8 wt% of ammonium polyphosphate (APP), EP/2PSiCN-8APP composite exhibited a limiting oxygen index value of 29.0% and passed a UL-94V-0 rating, which reached the refractory level. The thermogravimetric analysis confirmed that the addition of PSiCN and APP improved the thermal stability of the composites. The cone calorimetry test (CCT) revealed that the peak of heat release rate, total heat release, the peak of smoke production rate and total smoke production of EP/2PSiCN-8APP composite was reduced by 71.1%, 53.5%, 65.4%, and 53.5%, respectively, compared with pure EP. Furthermore, the residues after CCT were evaluated by scanning electron microscopy, laser Raman spectroscopy and Fourier transform infrared spectroscopy, and the flame retardant mechanism of EP/2PSiCN-8APP composite was proposed. Finally, the parallel arrangement of the aromatic ring and the surface of the PSiCN and the synergistic effect of the P/N/Si multi-element resulted in EP/2PSiCN-8APP with excellent mechanical properties.

Experimental analysis of the effect of natural fibers and SiC filler on the thermal behavior of green biocomposites

“…However, other factors like MLR, ignition temperature, reactivity with oxygen, and smoke production can also influence flammability. These results are confirms that combination of SiC and IFR can retard combustion and reduce heat release, which is in good agreement with the literature 51,53,57,58 …”

Synergistic effect of graphitic carbon nitride and ammonium polyphosphate on the enhanced flame retardant and smoke suppression properties of biobased polyamide 56

“…These phenomena can be ascribed to the premature thermal decomposition of the P‐N bonds. [ 49,50 ] These results indicate that g‐C 3 N 4 catalyzes the thermal decomposition degradation of APP, leading to the formation of abundant residues. Therefore, the char residue of CN@APP at 800°C is much higher than that of g‐C 3 N 4 and APP.…”

“…These phenomena can be ascribed to the premature thermal decomposition of the P-N bonds. [49,50] These results indicate that g-C 3 N 4 catalyzes the thermal decomposition degradation of APP, F I G U R E 2 Thermogravimetric analysis (TGA) (A) and DTG (B) curves of ammonium polyphosphate (APP), g-C 3 N 4 and CN@APP in a nitrogen atmosphere. DTG, derivative thermogravimetry F I G U R E 1 X-ray diffraction (XRD) patterns (A) and Fourier transform infrared (FT-IR) spectra (B) of ammonium polyphosphate (APP), g-C 3 N 4 and CN@APP leading to the formation of abundant residues.…”

“…CN@APP2 not only decreases the SPR, but also decreases the TSP, which indicates that CN@APP could improve the smoke suppression property of PA56. Moreover, compared with PA56/CN@APP1 and PA56/CN@APP3, the COP of PA56/CN@APP2 is less, which may be due to the two-dimensional nanosheet structure of g-C 3 N 4 exerts a physical barrier to the release of smoke, preventing the generation of CO. [49] However, excessive g-C 3 N 4 would show activity towards CO 2 photoreduction and converse CO 2 to CO, leading to higher COP of PA56/CN@ APP3. [57] The results prove that CN@APP2 remarkably reduces the fire hazards of PA56.…”

A new‐type terephthalonitrile derivative flame retardant of bi‐DOPO compound with hydroxyl and amino groups on epoxy resin

“…Traditional inorganic flame retardants (such as montmorillonite, 9 Al(OH) 3 , 10 and expandable graphite 11 ) need large amounts to reach flame resistance, which could easily lead to severe deterioration of mechanical properties. Ammonium polyphosphate, 12 widely used in recent years, could effectively improve the fire safety of EP, but the poor compatibility with the EP will greatly reduce its all-around performance. Based on the above research, it is vital to develop a new type of flame retardant with low addition amount to endowed excellent flame retardancy and maintain good mechanical properties.…”