Investigation of melt spinnability of plasticized polylactic acid biocomposites-containing intumescent flame retardant

Biodegradable polymers from renewable resources have attracted interest due to environmental pollution caused by the disposal of non-degradable polymers, and engineering them to produce fibres of textile grade can improve the environmental sustainability of textile sector. Flame retardancy of polylactic acid (PLA) can be improved if used in intumescent system containing acidic and carbonic source; however, spinning them to produce fibres of textile grade is a big challenge. We therefore have prepared PLA composites containing phosphorous-nitrogen-based flame retardant as acidic source together with kraft lignin as carbonic source. Different quantities of flame retardant and kraft lignin were added to PLA matrix by melt blending and then hot-pressed to form moulding sheets. A modified polyester-based plasticizer was also incorporated to facilitate the spinnability of the composites. Limiting oxygen index values and UL-94 ratings of the composites were reported. The melt spinnability of composites was then assessed, and flame retardancy of knitted structures produced from multifilament yarns was tested by cone calorimetry. Composites containing up to 7% (m/m) of lignin were spinnable together with 10% (m/m) of plasticizer. A substantial decrease of 59% in heat release rate was observed compared to pure PLA. The mechanism of intumescence was also reported.