Iron-montmorillonite and zinc borate as synergistic agents in flame-retardant glass fiber reinforced polyamide 6 composites in combination with melamine polyphosphate

This paper presents a preliminary investigation on the effects of organically modified iron-montmorillonite (Fe-OMT) and zinc borate (ZnB) on thermal degradation behaviors and flame retardancy of melamine polyphosphate (MPP) flame-retarded glass fiber reinforced polyamide 6 (GFPA6). The samples were characterized using limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR) and Microscale Combustion Calorimeter (MCC) measurements. The residue after LOI test was also analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy. A substitution of a certain fraction of MPP with ZnB or Fe-OMT can significantly improve the UL-94 rating of GFPA6/MPP composites from no rating to V0 rating, exhibiting excellent flame retardacny. Based on the investigations, different flame retardant mechanisms were proposed for the two effective flame-retardant formulations.