Photodegradation of partially oriented and drawn polypropylene filaments

Abstract

ABSTRACTThe effects of fiber structure on the process of photodegradation are controversial in the field. We tested polypropylene fibers of various form for their effects on photodegradation. Fiber grade polypropylene granules were spun into partially oriented multifilament yarns at a spinning speed of 2000 m min−1. The yarns were drawn using a draw‐twist unit. Yarns were exposed to ultra‐violet radiations in a covered open air chamber for different periods of time under two different sources of emissions (UVA; λ > 300 nm and UVC; λ = 254 nm). The samples were examined by Fourier transform infrared spectroscopy, mechanical testing, differential scanning calorimetry, microscopy, and density measurements. In photodegradation process, the drawn filaments had a longer induction time than undrawn ones. The mechanical properties of the undrawn yarns deteriorate faster than the drawn yarns. During the early periods of degradation helical content increases considerably, while the density fluctuates and increases. The degradation rate under UVC radiation was faster than under UVA radiation because of the higher energy of the UVC radiation. The upper photostability of the drawn yarns compared to the undrawn ones was due to the higher crystalline fraction and greater molecular orientation in the drawn yarn. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45716.