The Natural and Artificial Aging of Wire Jackets

摘要

The study shows that the principal factors affecting the degradation of nylon are ultraviolet light and heat. It has also been shown that natural outdoor aging leads to embrittlement and loss of tensile strength. The principal effect of exposure to ultraviolet light is that of cleavage of the molecule, while heat initially causes cross linking with subsequent cleavage. Moisture, while important in the instantaneous physical properties of nylon, plays no important role in the degradation of the molecule. The electrical tests on nylon sheets made under the conditions employed in this investigation are valuable in showing what happens in the nylon during exposure to various conditions of outdoor exposure and artificial aging. Information has been obtained on the leaching out of impurities under certain aging conditions and the production of ionizable reaction products under other aging conditions. The extreme avidity of the nylons for moisture has been emphasized by some of the observations made during the investigation. In the case of the other plastic samples, it is seen that these materials are very much more resistant to weathering than nylon, with the exception of the perbunan-vinyl compound. This material failed the mandrel-wrap test after 6 to 9 months' exposure.