Phytic acid and melamine-modified microcrystalline cellulose as effective flame retardants in polylactic acid...

This study introduces a novel bio-based flame retardant, MCC-GMA-PA-MEL, synthesized from microcrystalline cellulose (MCC) modified with phytic acid (PA) and melamine (MEL). Characterization of the resulting composites revealed a significant enhancement in PLA crystallinity to 35.9 %, driven by improved molecular mobility and heterogeneous nucleation effects. Flame retardancy assessments demonstrated a limiting oxygen index (LOI) of 25.7 % and a V-0 rating in the UL-94 test, highlighting the composite's effective flame-resistant properties. Furthermore, cone calorimetry results showed an increased ignition time, accompanied by a 15.7 % reduction in peak heat release rate (pHRR) and a 4.1 % decrease in total heat release (THR), along with improved thermal stability and greater char formation during combustion. Mechanical testing confirmed that the properties of PLA/MCC-GMA-PA-MEL remained comparable to those of pure PLA, emphasizing its practical applicability. These findings suggest that MCC-GMA-PA-MEL represents a promising sustainable bio-based flame retardant, suitable for use in biodegradable plastics and fibers, thereby advancing the development of environmentally friendly materials.