Characterization of structural changes in thermally enhanced Kevlar-29 fiber

This exploratory investigation examined the structural mechanism accounting for the enhanced compressive properties of heat‐treated Kevlar‐29 fibers. A novel theory was set forth that hydrogen‐bond disruption and concurrent misorientation of crystallites may account for the observed augmentation of compressive properties. To examine the said theory, as‐received Kevlar‐29 fibers were characterized by thermogravimetric analysis and differential scanning calorimetry in an effort to determine if crosslinking and/or hydrogen‐bond disruption was responsible for the improved behavior in compression. Additionally, Kevlar‐29 fibers that had been exposed to treatment temperatures of 400, 440, and 470°C were profiled by Fourier transform infrared spectrophotometry to determine if crosslinking and/or hydrogen‐bond obfuscation had been promoted. The results indicate that both mechanistic changes occurred within the Kevlar‐29, albeit in different regions of the rigid‐rod polymer. In particular, heat treatment of poly‐p‐phenylene terephthalamide appears to have resulted in crosslinking of its skin region and hydrogen‐bond disruption within the core realm. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 417–424, 2004