Water resistance, flame retardancy, and thermal properties of hydrophobic polypropylene/bamboo fiber composites

Melamine–formaldehyde resin-coated bamboo fiber (MFBF) and ammonium polyphosphate (MFAPP) were prepared, and then flame-retardant polypropylene (PP)/bamboo fiber composites based on MFBF/MFAPP were obtained by melt blending. The water resistance, flame retardant, and thermal properties of the composites were studied. The results show that MFBF and MFAPP have excellent water resistance with the water contact angles 130.85° and 119.78°, respectively. Compared with pure PP, the limit oxygen index (LOI) of the prepared composite increased from 18.5 to 25.5% with the UL-94V-0 rating. The peak heat release rate of the composite decreased from 1011.8 to 344.3 kW·m −2 and the total heat release decreased from 100.6 to 58.8 MJ·m −2 . Meanwhile, the total smoke release decreased from 1453.3 to 922.0 m 2 ·m −2 . After soaking in 70 °C water for 36 h, the composite still reached the V-0 rating in UL-94 test, demonstrating a good water resistance. This work provides an effective method to improve the water resistance and flame retardancy of PP/bamboo fiber composites. Graphical abstract Melamine–formaldehyde resin-coated bamboo fibers (MFBF) and ammonium polyphosphate (MFAPP) were prepared, then flame-retardant PP/BF composites were obtained based on MFBF/MFAPP. The results show that prepared composite exhibited excellent water resistance and flame-retardant properties.