Improved flame retardancy and smoke suppression properties of phenolic resin by incorporating MoO3 particles

Phenolic resin (PF) is widely used in aerospace, composite materials, and other fields. However, large amount of heat and smoke are produced during its combustion process, which is an important factor limiting its usage. To solve this problem, additive flame retardant MoO 3 has been incorporated into PF for improving its flame retardancy and smoke suppression properties. Thermogravimetric analyses results show that the T 5% of PF composites was gradually decreased from 264°C to 184°C and the char yield of PF-10% MoO 3 is 57 wt.%, higher than that of neat PF (50 wt.%). The PF composites with 10 wt.% MoO 3 passed UL-94 V-0 rating with a limiting oxygen index value of 29.8%. Meanwhile, the total heat release and total smoke production of PF-10% MoO 3 are 37.60 MJ/m 2 and 5.79 m 2 respectively, which are reduced by 30.5% and 24.8% compared with neat PF. Only 10 wt.% MoO 3 provide a 56.5% reduction (from 255 to 111) in maximal smoke density, meaning the good smoke suppression properties of MoO 3 . The pyrolysis products components are determined by thermogravimetric analysis combined with Fourier transform infrared spectroscopy. Furthermore, the micromorphology and chemical structure of char residue are also investigated by scanning electron microscopy, x-ray diffraction and Raman spectroscopy techniques. The promoting carbonization effect of MoO 3 significantly reduces the heat release and toxic smoke production of PF composites.