Improving the flame retardancy of polyamide 6 by incorporating hexachlorocyclotriphosphazene modified MWNT

Abstract

A nitrogen-, phosphorus-and chlorine-containing flame retardant, hexachlorocyclotriphosphazene (HCTP), has been covalently grafted onto the surface of multi-wall carbon nanotubes (MWNT) to obtain MWNT-HCTP. Polyamide 6 (PA6)/MWNT composites were then prepared via melt compounding. The flammability of PA6/MWNT composite was characterized by cone calorimetry, limiting oxygen index (LOI) and UL-94 tests. The results showed that peak heat release rate of samples containing 3 wt% MWNT-HCTP was only 460 kW/m 2 , which decreased by 35.2% compared with that of a neat PA6 sample. The LOI value was increased from 22.7% to 26.5%, and UL-94 test performance was also significantly improved by the presence of MWNT-HCTP. Scanning electron microscope (SEM) and optical microscope analysis showed that modified MWNT had a better dispersion and compatibility in PA6 than unmodified MWNT. The composition of residue chars and volatile products was investigated by SEM/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric-FTIR, respectively. It was proposed that grafted HCTP was mainly functioned in the condensed phase, where P, N can synergistically promote char formation and Cl element can catch free radicals to terminate the chain reaction during combustion of the PA6 composite.

Enhancing the flame retardancy of polyamide 6 by guanidine sulfamate‐modified carbon nanoparticles: Carbon nanotubes versus graphite oxide

“…The as‐received CNTs were firstly purified, shortened and acid‐modified according our previous work , obtaining acid‐modified MWNT (A‐MWNT, yield: 96.2%).…”

“…Some efforts have been made recently on improving the flame retardancy of functionalized carbon nanoparticles by grafting with FR . In our previous work, hexachlorocyclotriphosphazene has been successfully used to modify CNT and GO, and the modified carbon nanoparticles can efficiently improve the flammability and thermal stability of PA6 and EVA .…”

Fabrication and origin of new flame retarding bismaleimide resin system with low dielectric constant and loss based on microencapsulated hexaphenoxycyclotriphosphazene in low phosphorus content

“…4); besides, the characteristic absorptions of HPCTP, such as the P]N vibration (1070 cm À1 ), PeN (1265, 1195 cm À1 ) and PeO (945, 805 cm À1 ) [13,29], are found in the FTIR spectrum of MH, confirming the successful synthesis of MH. Fig.…”

“…Hexachlorocyclotriphosphazene is the most common phosphazene compound, but its low heat resistance and poor compatibility with the polymers withdraw its industrial application. Researchers substituted its Cl atoms with phenoxy groups to obtain hexaphenoxycyclotriphosphazene (HPCTP), which has been proved to have improved thermal stability [12,13]. Several research groups employed HPCTP to improve the flame retardancy of polyethylene [14], viscose fiber [15], and polystyrene [16].…”

Improving the flame resistance and thermal conductivity of ethylene‐vinyl acetate composites by incorporating hexachlorocyclotriphosphazene‐modified graphite and carbon nanotubes

“…To improve the compatibility and dispersion of carbon nanotube/graphite, functionalization with coupling agents, surface active agent, or even polymers is gaining particular interest . In our previous research, a nitrogen‐, phosphorus‐, and chlorine‐containing flame retardant—hexachlorocyclotriphosphazene (HCTP)—has been covalently grafted onto the surface of multiwalled carbon nanotubes (MWNTs) to improve both the compatibility and flame resistance of MWNT in PA6 . HCTP is a versatile starting oligomer for the synthesis of phosphazene‐based polymers as well as modifier for nanoparticles.…”