Fabrication of highly efficient phenylphosphorylated chitosan bio-based flame retardants for flammable PLA biomaterial

Modified chitosan (CS)-based flame retardants exhibit promising prospects owing to their sustainability, biodegradability, and good charring properties. A series of novel modified-CS bio-based flame retardants (phenylphosphorylated CS (PhPCS) and phenylphosphoramidated CS (PhPNCS)) were prepared by the phosphorylation and phosphoramidation reactions of CS with phenylphosphoryl dichloride and tetraethylenepentamine, respectively. Bio-based PhPCS and PhPNCS exhibited excellent flame retardancy efficiency for poly(lactic acid) (PLA). The limited oxygen index (LOI) values of the PLA/3 wt% PhPCS and PLA/3 wt% PhPNCS biocomposites increased to 29% and 27%, respectively, and they both achieved a V-0 rating during the UL-94 vertical combustion test. However, the mechanical properties of the PLA/PhPCS biocomposites decreased with increasing PhPCS content. The mechanical strengths of the PLA/PhPNCS biocomposites were better than those of the PLA/PhPCS biocomposites owing to the reactive compatibilization of the interface between the amino and carboxyl end groups of the PhPNCS nanoparticles and PLA matrix, respectively.

Automated summary

Modified chitosan-based flame retardants, such as phenylphosphorylated CS (PhPCS) and phenylphosphoramidated CS (PhPNCS), show promising prospects due to their sustainability, biodegradability, and good charring properties. These bio-based flame retardants exhibited excellent flame retardancy efficiency for poly(lactic acid) (PLA), but the mechanical properties of PhPCS-based biocomposites decreased with increasing content. On the other hand, PhPNCS-based biocomposites showed improved mechanical strengths due to the reactive compatibilization between the PhPNCS nanoparticles and PLA matrix.