NEXCEL Project Paper 19

Release time: 2024/07/26 Publisher： original Views：

Multifunctional phosphorus-containing imidazoliums endowing one-component epoxy resins with superior thermal latency, heat resistance, mechanical properties, and ffre safety

Introduction

Mr. Wang Jingsheng from Wuhan University of Technology, Ph.D Student of NEXCEL 2024 PHD project "Synthesis of phosphorus-containing metal- imidazole complex flame-retardant latent curing agents and their effect on the curing, flame retardancy and smoke suppression properties of epoxy resin" have published a paper entitled "Multifunctional phosphorus-containing imidazoliums endowing one-component epoxy resins with superior thermal latency, heat resistance, mechanical properties, and ffre safety" in "Chemical Engineering Journal" (SCI) recently.

Abstract

Epoxy resin (EP) possesses a high flammability risk, but the flame retardants applied often reduce other properties. For the sake of large-scale industrial manufacturing, EP and curing agent are increasingly being premixed as one-component system rather than blended immediately prior to application. However, current designs fail to break the trade-off between flame retardancy and mechanical/thermal/optical properties of one-component EPs. Herein, we developed a series of phosphorus-containing imidazolium compounds, named BADM-X (X = 1, 2, 3, and 4), which served as multifunctional latent hardeners for one-component EPs. BADM-1, BADM-2, BADM-3, and BADM-4 were synthesized in ethanol through the neutralization between bisphenol A diphosphate (BAD) and 2-ethyl-4-methylimidazole (EMI) at molar ratios of 1:1, 1:2, 1:3, and 1:4, respectively, which were easy to industrialize. Varying the imidazole content in BADM-X allowed for adjusting the curing reactivity and thermal latency of EP/BADM-X, making it adaptable for various applications. EP/BADM-2, EP/BADM-3 and EP/BADM-4 not only retained excellent optical properties, but also demonstrated increased glass transition temperatures (Tgs) and mechanical performances. The Tg of EP/BADM-2 reached 162.7 ℃, and its tensile and impact strengths increased by 34.8 % and 61.4 % relative to EP/EMI. EP/BADM-X exhibited enhanced fire safety, and the limiting oxygen index (LOI) and vertical burning (UL-94) classification of EP/BADM-2 reached 28.2 % and V-0, respectively. Besides, EP/BADM-2 demonstrated enduring flame-retardant and mechanical performances, thus showing great application potential. Overall, this study introduces a new class of multifunctional latent curing agents for the fabrication of durable fire-safe, high-performance, one-component EPs.

Paper Details

Chemical Engineering Journal 485 (2024) 149852

https://doi.org/10.1016/j.cej.2024.149852