Preparation of poly(melamine‐formaldehyde‐2,2′‐bis(trifluoromethyl)benzidine) high‐performance fibers

Melamine formaldehyde fiber is widely used in various fields because of its excellent heat resistance and flame‐retardant properties. In this study, melamine and paraformaldehyde are used as the main raw materials, 2,2′‐bis(trifluoromethyl)benzidine (TFMB) is successfully introduced into the molecular chain. The TFMB modified spinning solutions (MF‐TFMB) are obtained by one‐step copolymerization, the TFMB‐modified melamine‐formaldehyde fibers (MFF‐TFMB) are prepared by dry spinning. The surface contact angle and surface energy are measured by a contact angle measuring instrument. The thermal stability and mechanical properties of the fibers are measured by a thermogravimetric analyzer and a single‐fiber strength tester. The results show that the introduction of the TFMB group reduces the surface free energy of the polymer and effectively improves the heat resistance and mechanical properties of the fiber. When the addition amount of TFMB is 3%, the MFF‐TFMB‐3% fiber has smooth surface and bubble‐free inside, the breaking strength is 2.25 cN/dtex and the elongation at break is 11.85%. The limiting oxygen index is 32.5%, and the mass loss rate is decreased from 63.88% to 51.36% at 400°C. The fiber has excellent thermal stability and flame‐retardant properties.