The fracture of nylon 66 yarns which have been exposed to light

Abstract

It has been shown from earlier work in this laboratory that the fracture morphology of light-degraded, delustred nylon is different from that of unexposed, delustred nylon. This paper illustrates the effects on breaking strength, extension, and morphology of delustred and bright nylon yarns when exposed to daylight for different lengths of time and discusses what factors have influenced the breaking behavior of the samples. The scanning electron microscope (SEM) has been used to examine the broken filaments and has revealed a wealth of detail which would have been impossible to detect in a light microscope. Nylon 66, 17 dtex, semidull monofil was used throughout the initial experimental work and was exposed to daylight, from behind glass, for up to a maximum of 24 weeks during both the summer and winter months. Samples were removed after set exposure periods and tested to break on an Instron testing machine. The same monofil yarn was exposed before a xenon lamp to enable comparisons to be made between samples degraded by normal daylight and accelerated weathering conditions. Further samples of bright and dull nylon 66 yarns, exposed to daylight in Florida, have also been examined.