Fire-Resistant, Strong, and Green Polymer Nanocomposites Based on Poly(lactic acid) and Core–Shell Nanofibrous Flame Retardants

Despite extraordinary mechanical properties and excellent biodegradability, poly(lactic acid) (PLA) still suffers from a highly inherent flammability, restricting its wide applications in the electric and automobile fields. Although a wide range of flame retardants have been developed to reduce the flammability, so far, they normally compromise the mechanical strength of PLA. Herein, we have demonstrated the fabrication of a novel core–shell nanofibrous flame-retardant system, PN-FR@CNF, through in situ chemically grafting the phosphorus–nitrogen-based polymer onto the cellulose nanofiber (CNF) surface. The results show that adding 10 wt % PN-FR@CNF enables PLA to achieve a V-0 flame resistance rating during vertical burning tests and to exhibit a dramatically reduced peak heat release rate in cone calorimetry measurements, indicating a significantly reduced flammability. In addition, the tensile strength of PLA also increases by around 24% (about 72 MPa). This work offers an innovative methodology for th...