Photolytic Degradation of Textile Fibres in the Far Ultra-violet

Abstract

ALTHOUGH it is generally recognized that the action of far ultra-violet radiation on textile fibres is photolytic in character, investigations of the influence of oxygen and water vapour on the complex reactions involved have been mainly confined to cotton cellulose. The temperature of the system and the parameter of degradation are other factors which profoundly influence the nature of the results¹. In the experiments described here we have used as parameter the loss in tensile strength of the textile yarn which was exposed to the radiations from a low pressure mercury–vapour lamp emitting mainly at 2537 Å. The yarn was contained in the inner compartment of a brass cell fitted with a quartz window. The cell was maintained at a constant temperature by circulating a suitable heating (or cooling) medium through the outer compartment. During the experiment a stream of gas brought to the required temperature was passed through the cell. For the exposures (Fig. 1) in dry oxygen and nitrogen involving temperatures down to −60° C the quartz face of the brass cell formed part of the wall of an airtight lamp chamber. At the bottom of the chamber was a tray of phosphorus pentoxide to absorb moisture and prevent the deposition of ice on the cold quartz plate. In addition a stream of dry nitrogen was passed continuously through the chamber. For the experiments (Fig. 2) with dry and moist air in which the lowest temperature was 15° C, this procedure was unnecessary and the cell was irradiated in a large well ventilated cupboard. Where dry gases were used they were dried with phosphorus pentoxide. In experiments performed in air at 100 per cent relative humidity, air was bubbled through a sintered glass filter immersed in distilled water which was maintained at the same temperature as the cell.