Incorporation of cellulose with adsorbed phosphates into poly (lactic acid) for enhanced mechanical and flame retardant properties

We have engineered an environmentally sustainable, biodegradable, and flame retardant poly (lactic acid) (PLA) based composite by introducing resorcinol bis (diphenyl phosphate) (RDP) coated cellulose fibers at a mass fraction of only 8%. Mechanical testing showed that formation of the composite significantly improved the impact strength, dynamic and elastic moduli, and tensile strength relative to neat PLA. The composite self-extinguished in less than 2 s and had greatly reduced dripping, hence easily passing the UL-94 V0 criteria. Fourier Transform Infrared Spectroscopy (FTIR) was used to elucidate the chemical mechanism responsible for these effects, which were interpreted in terms of a dehydration process of cellulose in the presence of RDP. This has an overall cooling effect and reduction of the combustion, which can be observed in the reduction of heat release rate (HRR) by cone calorimetry and increase in limiting oxygen index (LOI) value.