Flame retardant bamboo fiber reinforced polylactic acid composites regulated by interfacial phosphorus-silicon aerogel

Interfacial interactions play an important role in fiber reinforced composites. Bamboo fiber (BF) was coated using a phosphorus-silicon hybrid aerogel, identified as BF–SiP. The BF–SiP and ammonium polyphosphate (APP) were used to regulate the flame retardancy and mechanical properties of poly(lactic acid) (PLA). The PLA composites were characterized using thermogravimetric analysis, UL-94 vertical burning, limiting oxygen index (LOI) and cone calorimetry. Incorporating 8% APP generates a PLA blend which displays a UL-94 V2 rating and a LOI value of 27.5 vol%. PLA8/BF composites display the same UL-94 rating and decreased LOI values, while PLA8/BF–SiP composites display a UL-94 V0 rating and increased LOI values. Compared with the same quantities for PLA, the peak of heat release rate for PLA8/20BF–SiP, PLA8/20BF is decreased by 54% and 43%, which is 31% and 20% more than that for PLA8, respectively. Flame retardancy for PLA8/BF–SiP composites occurs in both the condensed phase and the gas phase. The presence of BF–SiP reduces the formation of C–O ethers and carbonyl compounds and increases the evolution of incombustible components such as H2O, as well as the combustion generating PO radical. In addition, the tensile and impact strength of the PLA8/20BF–SiP is increased from 71 MPa to 4.0 kJ/m2 to 87 MPa and 5.3 kJ/m2, respectively, compared with those containing 20% BF. In short, this work constructs a flame retardant and thermal insulation structure, SiP aerogel, on the surface of BF. The presence of BF–SiP improves the flame retardancy and mechanical properties of PLA composites.