Flame retardancy of basalt fiber-reinforced PBT composite: effect of red phosphorus and TiO 2 synergism

Light-weight and fire safety are crucial requirements for fiber-reinforced polymer composites used in mainly the logistics sector. Phosphorus-based FR agents can be one of the effective solutions to improve the flame retardancy properties of highly flammable poly(butylene terephthalate) (PBT) and its composites reinforcing with various high-performance fibers. In this perspective, the purpose of this study was to see how microencapsulated red phosphorus (mRP) affected the flame retardancy of a chopped basalt fiber (BF)-reinforced PBT composite. The composite samples were manufactured with the constant amount of BF (20 mass%) and mRP concentrations ranging from 5 to 20% by mass. A synergistic study between the mRP (14 mass%) and a neat TiO 2 (1 mass%) was also carried out. The TGA, cone calorimeter, LOI, and UL-94 V tests were used to characterize samples. Char residues of composites were analyzed via the ATR-FT-IR and SEM inspections. Test results released that the HRR values of PBT matrix and BF-reinforced PBT composite decrease while the char formation and the LOI values steadily increased with the incorporation of mRP. Remarkable decreases in fire performance parameters were observed between 23 and 55% while the highest residue (35.0%) were achieved with the mRP concentration of 20 mass%. The increment in LOI at about 50% and a V0 rating in the UL-94 V test were obtained when the added amount of mRP reached to 20 mass%. A synergism was seen between the mRP and TiO 2 in the condensed phase considering the results of MLC test. Graphical abstract