Liquid phosphorus-based bis-imidazole compounds as latent curing agents for enhancing thermal, mechanical, and flame-retardant performances of single-component epoxy resins

IF 6.3 2区化学 Q1 POLYMER SCIENCE

Polymer Degradation and Stability Pub Date : 2024-10-30 DOI:10.1016/j.polymdegradstab.2024.111066

Jingsheng Wang , Jun Wang , Fengyi Wang , Shuang Yang , Chaoqun Wu , Xi Chen , Kaiwen Chen , Pingan Song , Hao Wang , Siqi Huo

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引用次数: 0

Abstract

The escalating need for advanced, fire-resistant, single-component epoxy resin (EP) is fueled by its practicality and economic benefits, highlighting the necessity for the development of multifunctional flame-retardant latent curing agents. Herein, two liquid phosphorus-containing bis-imidazole compounds, PPDM and DPCMI, were synthesized as latent curing agents for EP, demonstrating multiple effects in improving latency, thermal stability, mechanical properties, and fire safety. EP/PPDM and EP/DPCMI showcased superior storage stability and rapid curing at moderate temperatures, with EP/PPDM standing out for its long shelf life of 7 d and being gelled within 18 min at 100 °C. The resulting thermosets presented increased glass transition temperatures (189.5 and 178.9 °C), due to the enhanced crosslinking densities. The presence of bis-imidazole groups in PPDM and DPCMI enabled EPs to form denser crosslinked networks, leading to improved mechanical strength and toughness. The limiting oxygen index (LOI) values of EP/PPDM and EP/DPCMI reached 29.5% and 29.0%, respectively. Compared to the control EP, EP/PPDM and EP/DPCMI showed 23.1% and 18.8% reductions in total heat release and 22.0% and 23.11% decreases in total smoke production. These results confirm the enhanced flame retardancy and smoke suppression of EP/PPDM and EP/DPCMI because of introducing phosphorus-containing groups. Even though the curing time was halved to 2.5 hours, EP/PPDM systems maintained satisfactory overall performances. Therefore, this work offers a scalable strategy for the fabrication of single-component EP systems combining rapid curing, satisfactory flame retardancy, and enhanced thermal stability and mechanical properties, aligning with the needs of industrial applications.

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液态磷基双咪唑化合物作为潜伏固化剂，用于提高单组分环氧树脂的热性能、机械性能和阻燃性能

由于单组分环氧树脂（EP）的实用性和经济效益，人们对先进的阻燃单组分环氧树脂（EP）的需求与日俱增，这凸显了开发多功能阻燃潜伏固化剂的必要性。本文合成了两种液态含磷双咪唑化合物 PPDM 和 DPCMI，作为 EP 的潜伏固化剂，在改善潜伏期、热稳定性、机械性能和防火安全方面表现出多重效果。EP/PPDM 和 EP/DPCMI 具有优异的贮存稳定性，并能在中等温度下快速固化，其中 EP/PPDM 尤为突出，它的保质期长达 7 天，并能在 100 °C 下 18 分钟内胶凝。由于交联密度的提高，所产生的热固性材料的玻璃化转变温度也有所提高（分别为 189.5 和 178.9 °C）。PPDM 和 DPCMI 中双咪唑基团的存在使 EPs 能够形成更致密的交联网络，从而提高了机械强度和韧性。EP/PPDM 和 EP/DPCMI 的极限氧指数（LOI）值分别达到 29.5% 和 29.0%。与对照 EP 相比，EP/PPDM 和 EP/DPCMI 的总放热量分别减少了 23.1% 和 18.8%，总产烟量分别减少了 22.0% 和 23.11%。这些结果证实，由于引入了含磷基团，EP/PPDM 和 EP/DPCMI 的阻燃性和抑烟性得到了增强。即使固化时间减半至 2.5 小时，EP/PPDM 系统仍能保持令人满意的总体性能。因此，这项工作为制造单组分 EP 系统提供了一种可扩展的策略，该系统兼具快速固化、令人满意的阻燃性、更高的热稳定性和机械性能，符合工业应用的需求。

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来源期刊

Polymer Degradation and Stability 化学-高分子科学

CiteScore

10.10

自引率

10.20%

发文量

325

审稿时长

23 days

期刊介绍： Polymer Degradation and Stability deals with the degradation reactions and their control which are a major preoccupation of practitioners of the many and diverse aspects of modern polymer technology. Deteriorative reactions occur during processing, when polymers are subjected to heat, oxygen and mechanical stress, and during the useful life of the materials when oxygen and sunlight are the most important degradative agencies. In more specialised applications, degradation may be induced by high energy radiation, ozone, atmospheric pollutants, mechanical stress, biological action, hydrolysis and many other influences. The mechanisms of these reactions and stabilisation processes must be understood if the technology and application of polymers are to continue to advance. The reporting of investigations of this kind is therefore a major function of this journal. However there are also new developments in polymer technology in which degradation processes find positive applications. For example, photodegradable plastics are now available, the recycling of polymeric products will become increasingly important, degradation and combustion studies are involved in the definition of the fire hazards which are associated with polymeric materials and the microelectronics industry is vitally dependent upon polymer degradation in the manufacture of its circuitry. Polymer properties may also be improved by processes like curing and grafting, the chemistry of which can be closely related to that which causes physical deterioration in other circumstances.