Self-assembled lignin-based flame retardant hybrids carrying Cu2+ for poly(lactic acid) composites with improved fire safety and mechanical properties

• Published in: International journal of biological macromolecules 2024-06, Vol.269, p.132141-132141, Article 132141
• Main Authors: Cao, Xianwu, Zhou, Yangsheng, Huang, Jingshu, Yu, Bin, Zhao, Wanjing, Wu, Wei
• Format: Article
• Language: English
• Subjects: adsorption; ammonia; Ammonium polyphosphate; ammonium polyphosphates; carbon dioxide; combustion; copper; crystal structure; electrolytes; Electrostatic mutual adsorption; fire safety; flame retardants; heat; hydrogen; impact strength; lignin; nitrogen; phosphorus; PLA; Polyelectrolyte complex; Polyethyleneimine; Smoke suppression; tensile strength
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2024.132141

To enhance the flame retardancy and mechanical performance of PLA, a polyelectrolyte complex predicated on lignin was obtained by electrostatic mutual adsorption of ammonium polyphosphate (APP), polyethyleneimine (PEI), and copper ions as raw materials. The FT-IR spectra and EDX analysis confirmed the successful synthesis of a lignin-based flame retardant hybrid (APL-Cu2+) containing copper, phosphorus, and nitrogen elements. The combustion test results showed that the peak heat release rate and total heat release of the PLA composite containing 12 wt% APL-Cu2+ were decreased by 15.1 % and 18.2 %, respectively, as compared to those of pure PLA. The char residue morphology observation revealed that the addition of APL-Cu2+ could promote the formation of a highly dense and stable graphitized char layer, while TG-MS detected the emission of refractory gases such as ammonia gas, carbon dioxide, and water during combustion. The strong hydrogen bonding between APL-Cu2+ and the PLA matrix kept the composite maintaining good strength and toughness. The tensile strength and impact strength of PLA/6APL-Cu2+ increased by 4.73 % and 65.71 %, respectively, due to its high crystallinity and good interfacial compatibility. This work provides a feasible method to develop biobased flame retardant hybrids for PLA composites with better fire safety and improved mechanical properties.