Imidazolium Phosphinate Ionic Liquids as Latent Curing Agents for Epoxy Resins
Tingting Xiao, Chen Tan, Gary Histand, Dongen Lin
Abstract
Latent imidazolium phosphinate ionic liquids (IMPILs) with innovative structures were developed as high-performance curing agents for one-component epoxy systems. These room-temperature liquid IMPILs exhibit exceptional compatibility with liquid epoxy resin (EP, E-51), overcoming the immiscibility limitations of conventional curing agents. These IMPILs efficiently cure EP (E-51) at moderate temperatures (109–180 °C) in the mass ratio range of 100:10–100:15, while maintaining storage stability with a 15-day pot life at 25 °C. The cured thermosets achieve impressive overall performance: tensile strength of 88 MPa (surpassing thermosets cured with 1-methylimidazole or 1,2-dimethylimidazole), good thermal stability ( T 10% = 374–407 °C), and unexpected flame retardancy (LOI = 30.7–35.1%, surpassing standard epoxy resins). This work establishes IMPILs as a novel class of liquid latent curing agents that satisfy both long-term storage requirements and excellent thermal-curing performance for advanced epoxy composites.