TYPICAL FRACTURE APPEARANCE OF BROKEN WOOL FIBERS AFTER SIMULATED SUNLIGHT IRRADIATION

After determining the wet bundle strength of sunlight irradiated wool, the broken fiber ends are evaluated optically by electron microscope. Three different modes of fiber fracture are identified. Due to the br eakage morphology, we assume that the histological wool components are damaged to a different extent as a function of irradiation time. Thus , the frequency of the breakage modes may serve to indicate the stage of fiber damage. We suppose that the initial step of photodamage is th e photooxidation of the internal lipids, because they are obviously mo dified after a very short time of irradiation, while the keratin compo nents are visibly intact. After long irradiation periods, the fibrous structure of the keratin fibrils is no longer recognizable.