Synthesis and application of a novel phosphoryl thiourea-containing flame retardant for epoxy resin
作者:Ge-Yun You、Hong-Wu He、Bin Feng、Yu-Ying Tang、Zhi-Quan Cheng、Fang-Fang Fan
DOI:10.1007/s11696-020-01086-5
日期:2020.8
A novel phosphoryl thiourea-containing flame retardant (PSN) was synthesized and fully characterized. The influences of PSN with different phosphorus content on diglycidyl ether of bisphenol-A epoxy resin (DGEBA) cured by 4,4′-diaminodiphenylsulfone (DDS) were comprehensively evaluated via the measurement of flame retardancy, thermal performance, and mechanical property. The results showed that PSN-modified DGEBA/DDS thermosets exhibited moderate changes in glass transition temperature and thermal stability, and PSN could catalyze DGEBA/DDS to produce more char residues under both nitrogen and air atmosphere. When the phosphorus content reached only 1.0 wt%, the PSN-modified DGEBA/DDS thermoset obtained limited oxygen index (LOI) value of 29.2%, and reached vertical burning (UL-94) rating of V-0, which exhibited more excellent flame retardancy than that of the neat DGEBA/DDS thermoset with LOI value of 22.5% and no UL-94 rating. Moreover, compared with DGEBA/DDS, PSN-1.5/DGEBA/DDS thermoset with phosphorus content of 1.5 wt% presented lower combustion parameters of peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR), which further showed that PSN could effectively enhance the flame retardancy of DGEBA/DDS epoxy thermosets. The investigation of flame-retardant mechanism revealed that a P/N/S synergistic effect was presented by PSN, which was reflected in the condensed phase via the increase in the phosphorus-containing char yield and the gas phase via the release of non-flammable gas such as NH3, SO2, and H2O. Additionally, PSN-modified DGEBA/DDS thermosets could maintain above 83% of Izod impact strength for DGEBA/DDS. The high flame-retardant efficiency, good smoke suppression performance, and less negative effect on Izod impact strength of DGEBA/DDS epoxy thermoset promise that PSN would be a potential flame retardant for DGEBA/DDS epoxy system.
合成了一种新型含磷硫脲阻燃剂(PSN),并对其进行了全面表征。通过测定阻燃性、热性能和机械性能,全面评估了不同磷含量的 PSN 对 4,4′-二氨基二苯砜(DDS)固化的双酚 A 环氧树脂二缩水甘油醚(DGEBA)的影响。结果表明,PSN 改性 DGEBA/DDS 热固性材料的玻璃化转变温度和热稳定性变化不大,PSN 在氮气和空气气氛下都能催化 DGEBA/DDS 产生更多的残炭。当磷含量仅为 1.0%时,PSN 改性的 DGEBA/DDS 热固性材料的有限氧指数(LOI)值为 29.2%,垂直燃烧(UL-94)等级为 V-0,与 LOI 值为 22.5%、无 UL-94 等级的纯 DGEBA/DDS 热固性材料相比,具有更优异的阻燃性能。此外,与DGEBA/DDS相比,磷含量为1.5%的PSN-1.5/DGEBA/DDS热固性材料的峰值热释放率(PHRR)、总热释放率(THR)和总烟雾释放率(TSR)等燃烧参数更低,进一步表明PSN能有效提高DGEBA/DDS环氧热固性材料的阻燃性能。阻燃机理研究表明,PSN 具有 P/N/S 协同效应,在凝结相中体现为含磷焦炭产量的增加,在气相中体现为 NH3、SO2 和 H2O 等不可燃气体的释放。此外,PSN 改性的 DGEBA/DDS 热固性塑料可保持 DGEBA/DDS 83% 以上的 Izod 冲击强度。DGEBA/DDS 环氧热固性材料的阻燃效率高、抑烟性能好,而且对 Izod 冲击强度的负面影响较小,因此 PSN 有望成为 DGEBA/DDS 环氧体系的一种潜在阻燃剂。