Synthesis of waterborne epoxy resin with diethanolamine-assisted succinimide for improving the strand integrity of polyimide filament

A water-soluble epoxy resin emulsion was synthesized by diethanolamine-assisted succinimide modified epoxy resin (DSEP) and used to reinforce the strand integrity of polyimide filament (PI). FTIR, XPS, and ¹ H NMR provide an evidence for the succinimide (SI) and diethanolamine (DEA) bonded onto the epoxy resin (EP) structure in the form of C-N-C. The DSEP emulsion shows high storage and dilution stability, with its particle size distribution and PDI of 118∼232 nm and 0.106∼0.638, respectively. Compared with DEA modified EP, DSEP exhibits better strand integrity for PI filament. The breaking strength of PI filament infiltrated by DSEP can reach 2.59 GPa, which is increased by 47.04% than that of PI filament, and is close to that of commercially available water-soluble polyimide resin (2.63 GPa). In addition, the fracture microstructure of PI filament further confirms that DSEP significantly reinforces the aggregation of PI filament. Importantly, there is no wire splitting phenomenon of DSEP reinforced PI filament after more than 200 times of friction. These benefit from the similar material groups of imide ring and benzene ring between DSEP and PI filament structure, as well as the strong hydrogen bonding interaction between them, as further confirmed by FTIR and SEM analysis.