Preparation of new phosphorus⁃nitrogen composite flame retardant and its application in TPU

doi:10.19491/j.issn.1001-9278.2024.09.015

Abstract

Abstract:

A phosphorus⁃nitrogen organic salt flame retardant （EP） was synthesized through a simple one⁃step reaction using etdronic acid as a phosphorus source （EA） and antiphenylenediamine （PPD） as a nitrogen source. Its structure was characterized by ¹H⁃NMR and FTIR spectroscopy. The flame⁃retardant TPU was prepared by mixing TPU with EP using a melt blending method， and its thermal stability， flame retardant performance， and mechanical properties were investigated. The results indicated that the addition of EP generated little effect on the thermal stability of TPU， and its flame retardancy was significantly improved. The flame⁃retardant TPU containing 3 wt.% EP （TPU⁃3% EP） obtained a limiting oxygen index of 28.40 vol.% and also achieved a UL 94 V⁃0 classification in the vertical burn experiment. The residual carbon yield （CY） was more than twice that of pure TPU. Compared with pure TPU， the total heat release and peak heat release rate of TPU⁃3% EP were reduced by 22.12% and 61.85%， respectively， and its effective combustion heat was also reduced. EP can enhance the flame⁃retardant performance of TPU mainly by catalyzing the condensation phase to form charcoal and isolate thermal oxygen exchange. Moreover， the free radical quenching effectiveness in the gas phase also generates a certain flame⁃retardant effect.

Key words: phosphorus?nitrogen organic salt flame retardant, thermoplastic polyurethane, flame retardancy

CLC Number:

TQ323.8

WEI Shenzhi, CHEN Juan, RAO Jie, ZHANG Yinghao, ZHOU Minjie, ZHANG Qi. Preparation of new phosphorus⁃nitrogen composite flame retardant and its application in TPU[J]. China Plastics, 2024, 38(9): 88-93.

Figures/Tables 14

Fig.1. Synthesis roadmap of flame retardant EP

Fig.2. FTIR of EP

Fig.3. 1H⁃NMR of EP

样品	LOI/%	UL 94 （3.0 mm）
样品	LOI/%	av⁃（t₁+t₂）/s	是否滴落	是否引燃脱脂棉	等级
TPU	21.5	>60	是	是	NR
TPU⁃1%EP	26.3	4.5	是	是	V⁃2
TPU⁃2%EP	27.2	3.7	是	是	V⁃2
TPU⁃3%EP	28.4	2.9	是	否	V⁃0

Tab.1. Burning data of the samples

Fig.4. （a） HRR （b） THR （c）Mass （d）MLR of TPU and TPU⁃3%EP；top and side digital photographs of carbon layers of （e） TPU and （f） TPU⁃3%EP after conical calorimetric testing

样品

点火时间/s

总热释放量/

MJ·m^-²

热释放速率峰值/

kW·m^-²

平均CO产率/

kg·kg^-1

质量损失/

kg·kg^-1

平均有效燃烧热/

MJ·kg^-1

Tab.2. Cone calorimeter results for TPU and TPU⁃3%EP samples

Fig.5. SEM of carbon residues of （a） TPU and （b） TPU⁃3EP at different magnifications

Fig.6. Raman spectrum of residual carbon of （a） TPU and （b） TPU⁃3%EP after CCT

Fig.7. Digital photographs of TPU and TPU⁃3%EP stored in a muffle furnace at different temperatures for 15 min

样品	样品质量/g	剩余质量/g	残炭量/%
TPU	3.04	0.03	0.99
TPU⁃3%EP	3.09	0.18	5.82

Tab.3. Char residue data of TPU and TPU⁃3%EP stored at 600 ℃ for 15 min in a muffle furnace

Fig.8. （a） TG and （b） DTG curves of TPU and TPU⁃3%EP

样品	T_5%/℃	T_50%/℃	T_max/℃	残炭量/%
TPU	283.94	395.09	400.09	10.11
TPU⁃3%EP	268.36	405.86	404.61	21.31

Tab.4. TG data of TPU and TPU⁃3%EP

Fig.9. Stress⁃strain curves of TPU and TPU⁃3%EP

样品	拉力/N	断裂伸长率/%	拉伸强度/MPa
TPU	191.1	1 065.5	19.6
TPU⁃3%EP	133.3	950.9	14.1

Tab.5. Mechanical properties of TPU and TPU⁃3%EP

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