Flammability and Thermal Properties of a Novel Intumescent Flame Retardant Polypropylene

A novel intumescent flame retardant system (IFRs) combines Tri (1-oxo-2,6,7-trioxa-1-phosphabicyclo [2. 2. 2] octane-methyl) phosphate (TPMP) with melamine pyrophosphate (MPOP) and its application in polypropylene (PP) has been investigated. The thermal stability, flammability, and water resistance were studied by thermogravimetric analysis (TGA), UL-94 test, and cone calorimetry. TGA shows that pure PP degrades at about 400 degrees C, while sample PP-6 degrades at about 270 degrees C under nitrogen atmosphere. With 30wt% total loading of the IFRs, sample PP-6 passes the UL-94 V-0 test. It can still pass the UL-94 V-0 test after the water treatment. The introduction of TPMP and MPOP strongly decreases the peak heat release rate (PHRR) value of the flame retardant (FR) PP composite. The morphologies of the char residues obtained after cone calorimetry were investigated by means of scanning electron microscopy (SEM). The char residue of sample PP-6 has better structure, which prevents the underlying materials from further decomposing. X-ray photoelectron spectroscopy (XPS) was used to further explore the char residues of the FR PP composites. The results show that sample PP-6 has the best char residue, which enhances the oxidation resistance of the char layer.