Synthesis of spinnable melamine formaldehyde resin prepolymer using ionic liquid and performance regulation of melamine fibers

In order to address the poor spinnability of melamine formaldehyde (MF) resin spinning dope, 1-ethyl-3-methylimidazolium diethylphosphate ([Emim]DEP)/H2O solution is first used as the solvent to synthesize MF resin prepolymer (pre-MF) solution. The pre-MF solution can be directly spun into fibers without any fiber-forming agent. The influence of synthetic parameters, such as reaction time and temperature, the mass ratio of [Emim]DEP to H2O, and solid content, on the fiber properties are investigated systematically. The results show that [Emim]DEP demonstrates a key role in regulating the molecular weight and distribution of pre-MF solution, which plays transfer catalyst effect during the synthesis process. Furthermore, programmed heating is the most helpful for the linear growth of the molecular in the initial stage of curing and the formation of the final cross-linked structure. The fibers obtained under optimal conditions have excellent mechanical properties, with fracture strength of 323.8 MPa and elongation at break of 7.2%. This work provides a novel synthesis method of pre-MF solution to prepare high-performance MF fibers.