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 MoO3 has been incorporated into PF for improving its flame retardancy and smoke suppression properties. Thermogravimetric analyses results show that the T5% of PF composites was gradually decreased from 264°C to 184°C and the char yield of PF-10% MoO3 is 57 wt.%, higher than that of neat PF (50 wt.%). The PF composites with 10 wt.% MoO3 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% MoO3 are 37.60 MJ/m2 and 5.79 m2 respectively, which are reduced by 30.5% and 24.8% compared with neat PF. Only 10 wt.% MoO3 provide a 56.5% reduction (from 255 to 111) in maximal smoke density, meaning the good smoke suppression properties of MoO3. 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 MoO3 significantly reduces the heat release and toxic smoke production of PF composites.

Controllable fabrication of a hybrid containing dodecyl dihydrogen phosphate modified magnesium borate whisker/hydrated alumina for enhancing the fire safety and mechanical properties of epoxy resin

A composite particle with hydrated alumina deposited on the surface of magnesium borate whisker (MBW@HA) was prepared following a chemical liquid deposition method. Subsequently, dodecyl dihydrogen phosphate (DDP) was grafted onto the surface of the composite particles to synthesize an inorganic–organic hybrid (MBW@HA–DDP). The structure, morphology, and composition of MBW@HA–DDP were well characterized. The results revealed the hybrid of MBW@HA–DDP was successfully synthesized characterized by a hydrophobic surface. Subsequently, the obtained MBW@HA–DDP was incorporated into epoxy resin (EP) to fabricate flame retardant composites. The results revealed that the incorporation of MBW@HA–DDP significantly improved the fire safety of EP, for instance, the total heat release (THR) and peak heat release rate (PHRR) of the EP composite with 10-phr MBW@HA–DDP added were reduced by 28.1% and 32.0%, respectively, accompanied with lower total smoke production (TSP) and smoke production rate (SPR). The improved fire safety was due to the barrier function of MBW and HA, and the dilution effect of water vapor generated from HA. Meanwhile, the phosphorus oxoacids generated from DDP could function as catalysts and increase the degree of graphitization of the char residues, thus protecting the matrix effectively. In relation to mechanical properties, the incorporation of MBW@HA–DDP did not deteriorate the mechanical properties of EP but improved them to some extent. The results presented herein help develop a novel strategy for developing flame retardants characterized by good flame-retardant behavior and improved mechanical properties.

A novel hybrid containing dodecyl dihydrogen phosphate modified magnesium borate whisker/hydrated alumina (MBW@HA–DDP) was fabricated with good flame retardant and reinforcing properties for epoxy resin (EP).