Aramid nanofiber-reinforced thermotropic polyarylate nanocomposites with improved thermal and long-term mechanical performance

We report the influences of aramid nanofiber (ANF) on the thermal stability and long-term mechanical performance of thermotropic polyarylate (TPAR) nanocomposites. For this purpose, ANFs with an average diameter of 24.6 nm were fabricated through a deprotonation process of short aramid fibers in KOH/DMSO solution, and they were composited with TPAR via masterbatch melt-compounding to attain a series of nanocomposites with 3–15 wt% ANF loadings. The SEM images revealed that ANFs were well dispersed in the microfibrillar TPAR matrix of the nanocomposites with 3–5 wt% ANF, but they tended to aggregate partially in the nanocomposites with higher ANF loadings of 7–15 wt%. Nonetheless, specific hydrogen bonding interactions were found to exist between the amide group of ANFs and the ester group of the TPAR chains in the nanocomposites. Accordingly, ANFs contributed to enhancing the glass transition temperature of the nanocomposites by restricting the chain mobility of the TPAR matrix, and they also accelerated the melt-crystallization of TPAR by serving as nucleating agents. From the stepped isothermal method and dynamic mechanical analysis, the TPAR-based nanocomposite with 5 wt% ANF was characterized to have the maximum elastic modulus and long-term mechanical durability due to the trade-off effect of the specific hydrogen bonding interactions and the dispersibility of ANFs in the TPAR matrix.