Xu, YZ (reprint author), Peking Univ, Dept Chem, State Key Lab Rare Earth Mat Chem & Applicat, Beijing 100081, Peoples R China.
Because the melting temperature of aramid is higher than its thermo-decomposition temperature, processing of aramid fiber in the molten state is not feasible. Here we propose an approach to process aramid fiber using infrared Free Electron User(FEL). The temporal structure of the FEL pulses allows the fiber to be excited to higher vibrational levels so that the polymer becomes soft enough to be processed without significant thermo-decomposition. Microscopic observation using convention optical microscope and polarized technique shows that "necking phenomenon" and re-orientation occur on an aramid fibrous sample that was treated with FEL under external strain. In comparison with the the sample without treatment of FEL, significant changes are observable on the morphology of the broken aramid fiber treated with FEL. The above results strongly suggest that the aramid fiber is molten under the excitation of FEL. FTIR spectroscopic studies show that no thermal decomposition was observed on the aramid sample after FEL treatment. The above result may be helpful to develop a new way to process aramid in the future.