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

Abstract

Seeking a facile strategy to synthesize efficient and inexpensive flame retardant which endows biobased polyamide 56 (PA56) with desirable flame retardancy is an urgent need. Here, ammonium polyphosphate (APP) was modified with graphitic carbon nitride (g-C 3 N 4 ) to synthesize a nitrogen-phosphorus flame retardant (CN@APP) and then applied in biobased PA56. The X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectra demonstrated that APP was successfully microencapsulated with g-C 3 N 4 . The micromorphology structure was further characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PA56/CN@APP attained a UL 94 V-0 rating and limiting oxygen index (LOI) value of 31.7%. A sharp reduction of 35.3% in peak heat release rate (pHRR) and 24.0% in total heat release (THR) and an 874% increase in char yield were noticed for PA56/CN@APP2 compared with pure PA56. Additionally, the peak smoke production rate (pSPR) and total smoke production (TSP) of PA56/CN@APP2 were 33.0% and 21.8% lower than those of pure PA56. Scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were employed to analyze the condensed phase residues from the cone calorimeter test (CCT). The results indicated that CN@APP was beneficial for forming a more stable and compact carbon layer during combustion, thereby insulating the heat transfer and improving the flame retardancy and smoke suppression of PA56.

Synergistic fire retardancy of melamine resin modified with pentaerythritol and ammonium polyphosphate in PP

“…41 The combined analysis of HRR and THR data allows a more comprehensive evaluation of the fire retardant effect and burning behavior of fire retardant composites. 42,43 As can be shown in Figure 2, the HRR of the neat PP increases fast with the increased combustion time and the PHRR appears at 117 s. The PHRR and MHRR are 1216.0 and 410.2 kW/m 2 , respectively. Furthermore, the complete burning time (T CB ) is about 372 s. The slope of the linear part of the THR curve is very high.…”

“…HRR and THR are two critical parameters for the evaluation of the fire intensity, and the slope of the linear part of the THR curve is related to the fire propagation tendency of the material, the larger the slope, the easier the fire propagation 41 . The combined analysis of HRR and THR data allows a more comprehensive evaluation of the fire retardant effect and burning behavior of fire retardant composites 42,43 …”

Synergistic flame retardant modification of bio‐based nylon 56 by graphitic carbon nitride and melamine cyanurate

“…There is a great deal of unpolymerized amino groups in g-C 3 N 4 , which have abundant nonbonding electrons and can be combined with NH 2 of MCA through electrostatic attraction. 38 The shift of the functional group NH 2 in g-C 3 N 4 promotes hydrogen bonding. 39 For CNMCA, the peaks at 3162 cm À1 disappeared, and the peaks at 3000-3500 cm À1 moved to a lower wavenumber due to the stretching vibration of NH 2 , which illustrates that g-C 3 N 4 is wrapped on the surface layer of MCA by intermolecular hydrogen bonding.…”

Bio‐based Polyamide 56: Recent advances in basic and applied research

“…By modifying PA56 with flame retardants, scientists have prepared a series of materials with excellent flame retardant properties, laying the foundation for subsequent research and use. Zhang et al 70 used ammonium polyphosphate (APP) modified with graphitic carbon nitride (g‐C 3 N 4 ) to synthesize a nitrogen–phosphorus flame retardant and named it “CN@APP”. PA56/CN@APP achieved a UL 94 V‐0 rating and a limiting LOI of 31.7%.…”