High‐modulus polyaramide and polybenzimidazole blend fibers

Polymer blends from polybenzimidazoles (PBI) and high‐performance polyaramides were spun to give a PBI variant with better tensile properties than PBI itself. Infrared absorption spectra of a hot‐drawn fiber showed 10‐wavelength shift at the carbonyl band, CO, of high‐modulus polyaramide (HMA) due to an interaction of the CO with NH. Dynamic mechanical analysis (DMA) also confirmed the interaction is at a molecular level. The mechanical properties of hot‐drawn fibers from PBI/HMA polymer blends obey Halpin and‐Tsai's theory. Hot‐drawing “immediately after” dry‐spinning yielded fibers with impressive properties. Aging as‐spun PBI/HMA fibers was very harmful for fiber tensile properties. The effects of sulfonation and heat setting on fiber thermal and mechanical properties are also reported.