An effective intumescent flame retardancy of LDPE induced by the combination of APP and CNCO-HA

A char-forming agent poly(4,6-dichloro-N-hydroxyethyl-1,3,5-triazin-2-amine-1,6-diaminohexane) (CNCO-HA) containing triazine rings was chosen for improving the flame retardant of low density polyethylene (LDPE). The synergistic effect of CNCO-HA and Ammonium polyphosphate (APP) on the flame retardancy and char-forming behavior of LDPE were investigated. The limited oxygen index (LOI) and vertical burning test (UL-94) results indicated the optimal weight ratio of APP to CNCO-HA was 3:1, and the LOI value of composite reached 31.0% with 30% intumescent flame retardant (IFR) loading. The cone calorimeter test analysis revealed that IFR presented excellent char forming and smoke suppression ability, and resulted in the efficient decrease of combustibility parameters. The thermogravimetric analysis results demonstrated that IFR reduced the thermal degradation rate at main stage of degradation. Scanning electron microscopy observed that IFR promoted to form a compact and continuous intumescent char layer. The Laser Raman spectroscopy spectra showed that larger graphitization degree was formed to enhance the strength of char, and Fourier transform infrared results presented that P-O-C and P-O-P structures in the residue char were formed to improve shield performance of the char layer to obtain better flame retardant properties of the composite. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43950.