Kevlar Photochemical Degradation Mechanisms

摘要

The objective of this program was to investigate and determine Kevlar's photochemical degradation mechanisms, rate constants, and activation energies in air. The underlying reason was to understand the oxidative photodegradation processes, which would help to provide service life forecast under the sunlight conditions and to aid effective method development against its photodecomposition. The first significant accomplishment of the project was the new and novel analytical approach, which demonstrated the rate constant and activation energy determinations of Kevlar's photooxidative processes. The 0.2 atm of oxygen-18-labeled environment in a solar chamber simulates the air exposure under sunlight conditions. The technique also allows the radial Oxygen 18 distribution measurement from the fiber surface toward the fiber center. The data from the accelerated experimental conditions in the solar chamber in an diatomic oxygen 18 atmosphere are differentiated from the similar ambient daylight exposure effects. The second significant accomplishment was the recognition of a thermal decomposition pattern of Kevlar in concentrated sulfuric acid at 196 C to give the same two types of decarboxylations: one yields one mole of Carbon dioxide per (C7H5NO) moiety and the other gives two moles of CO2 per (C7H5NO) moiety. The third significant accomplishment was the analytical methodology applied to deduce the four photooxidative processes.