Flame retardancy and thermal degradation behavior of efficient intumescent flame retardant LDPE composite containing 4A zeotile

•4A presented excellent synergistic effect on the flame retardant and smoke suppression ability.•TGA/MS results indicated that 4A apparently promoted to release more NH3 at early degradation stage, but reduced side chain fragmentation in the main thermal degradation stage.•The flame retardant mechanism researches showed that 4A improved the compactness and strength of char with higher graphitization degree and more connected structures containing P and O.

The influence of 4A zeolite (4A) on the flame retardancy and thermal degradation behavior of efficient intumescent flame retardant low density polyethylene composites (LDPE/IFR) was investigated by the means of limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), thermogravimetric analyzer coupled to a mass spectrometer (TGA/MS), cone calorimeter test (CCT), digital photos, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and laser raman spectroscopy (LRS). It was found that 4A dramatically enhanced the LOI value of the LDPE/IFR and all composites passed the UL-94 V-0 rating test. The TGA and TGA/MS results indicated that 4A apparently promoted to release more NH3 at early stage, but reduced the main products intensity in the main degradation stage. Also, it enhanced the fire retardant performance with a great reduction in combustion parameters of LDPE/IFR composite from CCT test. The morphological structures observed by digital and SEM photos indicated that 4A promoted LDPE/IFR to form more compact and continuous char layer. The LRS and EDS analysis revealed that the compactness and strength of the char surface containing 4A was improved, and higher graphite degree was formed with remaining more P and O to increase the crosslinking degree.