A wrapped nano-flame retardant composed of carbon nanotubes and phosphorus-nitrogen containing polymer: synthesis, properties and flame-retardant mechanism

A nano-flame retardant (PCP-CNT) with the phosphorus-nitrogen containing polymer (PCP) wrapped nanotubes (CNTs) was produced via strong π-π stacking interactions between the walls of CNTs and PCP polymerized with hexachlorocyclotriphosphazene (HCCP) and p-phenylenediamine (p-PDA). The structures and properties of PCP-CNT were characterized by infrared absorption spectrum (FTIR), solid 1H nuclear magnetic resonance spectroscopy (1H NMR), transmission electron microscopy (TEM) and thermal gravimetric analysis tests (TGA). The flame retardancy of the flame-retardant polybutylene terephthalate (FR-PBT) was studied via limited oxygen index (LOI) and cone calorimeter (CONE) tests. The pk-HRR of FR-PBT was significantly reduced by 59.8 and 69.4% with the addition of 10 and 15% PCP-CNT, respectively. In addition, the thermal degradation mechanism of the pristine PBT and FR-PBT were discussed by using Ozawa method.