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