Facile synthesis of a novel transparent hyperbranched phosphorous/nitrogen-containing flame retardant and its application in reducing the fire hazard of epoxy resin

• Published in: Journal of hazardous materials 2019-11, Vol.379, p.120793, Article 120793
• Main Authors: Hu, Xin, Yang, Hongyu, Jiang, Yuping, He, Hualing, Liu, Hongyin, Huang, Hao, Wan, Chaojun
• Format: Article
• Language: English
• Subjects: Epoxy composite; Fire safety; Flame retardant; Hyperbranched compounds; Transparency
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.120793

[Display omitted] •A novel hyperbranched P/N-containing flame retardant (HPNFR) was facilely synthesized via a transesterification reaction of DMMP and THEIC.•The synthesized hyperbranched flame retardant showed high flame retardant efficiency for epoxy resin.•EP with only 4.0 wt% of HPNFR can pass UL-94 V-0 rating and possess LOI value as high as 34.5%.•The fabricated EP/HPNFR composites not only possess high fire safety, but also maintain high transparency. In this study, a novel hyperbranched phosphorus/nitrogen-containing flame retardant (HPNFR) was facilely synthesized via the transesterification reaction of dimethyl methylphosphonate and tris (2-hydroxyethyl) isocyanurate and characterized successfully by 1H NMR and FTIR. The sample with 4 wt% HPNFR can achieve V-0 rating in UL-94 test and possess a LOI value as high as 34.5%. Conspicuous blowing-out effect was observed during the vertical burning test. TG results indicated that the presence of HPNFR significantly improved the thermal stability of EP thermosets. From cone test, THR, p-HRR, p-SPR and TSP values of HPNFR/EP composites were decreased in comparison to those of pure EP, revealing the reduced fire hazard of EP composites with HPNFR. SEM images of EP thermoset with 4 wt% of HPNFR after cone test exhibited compact and continuous char layers, while those of pure EP are fragmentary and broken. From TG-IR test, the yield of toxic CO and other pyrolysis products was significantly reduced, indicating a decrease in toxicity. Phosphorus-containing compounds were detected in gas phase, which verified the gaseous phase flame retardant effect of HPNFR. Besides, HPNFR would not significantly damage the transparence of EP thermosets, consequently reserved it’s application value in some special fields.