Atomic oxygen-resistant polyimide composite fibers based on wet spinning of polyamic Acid-POSS ammonium salts

Publication date: Available online 5 September 2019Source: Polymer Degradation and StabilityAuthor(s): Fangfang Liu, Haiquan Guo, Yong Zhao, Xuepeng Qiu, Lianxun Gao, Yanna ZhangAbstractAs a vital component of flexible cables in aerospace vehicles, outstanding atomic oxygen (AO) resistance is in demand for polyimide (PI) fibers. Herein, a series of PI composite fibers with different polyhedral oligomeric silsesquioxane (POSS) ammonium salt contents (0–20 wt%) is prepared by adding diethylamino-POSS into polyamic acid (PAA) solution followed by spinning via wet process. The average silicon contents of the fibers by ICP (i.e., 2.99 wt%) are similar to the surface silicon content (2.93 wt%) measured by XPS. The interaction between positive charges from diethylamino-POSS and negative charges from PAA chains gives rise to the even dispersion of diethylamino-POSS in PI composite fibers. All the composite fibers exhibit Tg at ∼396 °C and T5% at ∼553 °C. Moreover, the fracture strength slightly increases from 0.57 GPa to 0.63 GPa with increasing POSS ammonium salt content from 0 wt% to 15 wt%. After AO erosion, SEM results exhibit lower roughness for composite fibers than pure PI fibers. As the ammonium salt content is increased from 0 wt% to 20 wt%, the lower mass loss with 0.15 mg cm−2 is shown, and the retention rates of fracture strength and initial modulus are considerably improved from 59.65% to 89.09% and from 63.83% to 91.45%, respectively....
Source: Polymer Degradation and Stability - Category: Chemistry Source Type: research