Facile synthesis of phosphoramide salts as flame retardants for Poly(lactic acid) with enhanced crystallization and retained tensile properties

Xiulin Li; Dequn Wu; Xueli Wang; Jianyong Yu; Faxue Li; Ruchao Yuan

doi:10.1016/j.ijbiomac.2025.143398

Facile synthesis of phosphoramide salts as flame retardants for Poly(lactic acid) with enhanced crystallization and retained tensile properties

Int J Biol Macromol. 2025 May;310(Pt 3):143398. doi: 10.1016/j.ijbiomac.2025.143398. Epub 2025 Apr 22.

Authors

Xiulin Li¹, Dequn Wu¹, Xueli Wang², Jianyong Yu², Faxue Li³, Ruchao Yuan⁴

Affiliations

¹ Shanghai Frontier Science Center of Advanced Textiles, Donghua University, Shanghai 201620, China; College of Textiles, Donghua University, Shanghai 201620, China.
² Innovation Center for Textile Science and Technology, Donghua University, Shanghai 201620, China.
³ Shanghai Frontier Science Center of Advanced Textiles, Donghua University, Shanghai 201620, China; College of Textiles, Donghua University, Shanghai 201620, China; Innovation Center for Textile Science and Technology, Donghua University, Shanghai 201620, China. Electronic address: fxlee@dhu.edu.cn.
⁴ Shanghai Frontier Science Center of Advanced Textiles, Donghua University, Shanghai 201620, China; College of Textiles, Donghua University, Shanghai 201620, China. Electronic address: rcyuann@dhu.edu.cn.

PMID: 40274158
DOI: 10.1016/j.ijbiomac.2025.143398

Abstract

The improvement of both the inherent combustibility and crystallization characteristics of PLA has long posed a significant challenge. In this study, this issue was effectively addressed through the facile synthesis of a series of phosphoramide salts containing phosphoryl groups, termed PPA-X (where X represents the corresponding diamine), using phenylphosphoric acid instead of phenylphosphonic dichloride. This approach avoided the typical problems associated with traditional flame retardants containing phosphoryl groups, including highly vigorous reactions, the need for acid-binding agents, and the generation of corrosive hydrogen chloride gas. A 3 wt% loading of PPA-P-phenylenediamine (PPA-PPD) enabled PLA to self-extinguish within 1 s, achieve V-0 rating in vertical burning tests, and attain a limiting oxygen index (LOI) of 27.1 %. Moreover, the crystallization half-time (t_1/2) at 115 °C for PLA was significantly reduced from 22.9 min to 12.5 min, while its crystallinity increased from 13.8 % to 41.2 %. Importantly, the tensile strength and elongation at break of PLA were well-preserved. Overall, this study presents a simple and low-toxicity strategy for developing highly effective flame retardants and nucleating agents for PLA, with promising potential for industrial applications.

Keywords: Crystallization rate; Flame retardant; Phosphoramide salt; Poly(lactic acid).

MeSH terms

Crystallization
Flame Retardants* / chemical synthesis
Phosphoramides* / chemical synthesis
Phosphoramides* / chemistry
Polyesters* / chemical synthesis
Polyesters* / chemistry
Salts / chemical synthesis
Salts / chemistry
Tensile Strength

Substances

Flame Retardants
Polyesters
poly(lactide)
Phosphoramides
Salts