Reciprocity and spectral effects of the degradation of poly(ethylene‐terephthalate) under accelerated weathering exposures

Abstract

Exposures of poly(ethylene‐terephthalate) (PET) films were performed under xenon‐arc (full spectrum) and fluorescent UVA‐340 (UV only) irradiation to investigate the reciprocity principle and wavelength dependence of photodegradation in weathering. When the intensity of full spectral irradiance is increased from 5× to 50×, the reciprocity principle is not obeyed in this material system. The change in optical properties for PET is attributed to the corresponding longer exposure time of the 5× exposure that allows oxidative reactions to occur at lower irradiance. Full spectrum xenon‐arc and fluorescent UVA‐340 lamps have different spectral distributions and samples exhibits different material degradation mechanisms under each source. The UVA‐340 exposure leads to more pronounced degradation relative to the full spectrum xenon‐arc. This study shows that intensification of a single stressor in lab‐based weathering experiments to accelerate degradation and the use of differing light sources are not sufficient to allow reliable determination of service lifetime of polymeric materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47589.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

“…Other polymers such as high-density polyethylene (HDPE), however, show a dependence of UV radiation dose on the increase in surface crystallinity, but not on changes in bulk strength or stiffness [ 485 ]. The same lack of a linear dependence for some of the properties was reported for photodamage of poly (ethylene terephthalate) [PET] [ 489 , 490 ] as well as for HDPE [ 491 ] in accelerated weathering. It is critical to establish the dependence of damage on dose for individual properties of interest.…”

“…Evaluations of laboratory-accelerated weathering have been routinely used to assess outdoor degradation rates of common plastics such as polyethylene (PE) [ 485 ], polypropylene (PP) [ 486 , 487 ], polycarbonates (PC) [ 488 ] and polyesters (PET) [ 489 , 490 ]. These weathering procedures rely on elevated temperature and higher light intensity relative to natural exposures.…”

“…Recent work has focused on two modelling approaches: (1) A model that consists of a series of terms, typically one for each environmental stressor, usually following the observed behaviour for that stressor (e.g., temperature with the Arrhenius model; see recent versions in e.g., [ 489 , 490 , 493 , 494 ]. The challenge with this approach is in interpreting the interacting effects between different environmental stressors (e.g., temperature and moisture may have a synergistic effect).…”

Weathering and Material Characterization of ZTO/Ag/ZTO Coatings on Polyethylene Terephthalate Substrates for the Application of Flexible Transparent Conductors

“…The analyzed results shown in Figure 7b illustrate that the change in the 1102 cm −1 /1119 cm −1 intensity ratio as a function of exposure time was the same between the OMO sample and the PET substrate. This illustrates that the loss of mechanical integrity of the OMO samples after weathering is mainly caused by the aging degradation of the PET substrate upon UV exposure [10][11][12].…”

“…Moreover, the substrate surface of commercial PET products used in outdoor applications is usually coated with a transparent inorganic layer (e.g., SiOx or Al 2 O 3 , usually several nanometers in thickness) that hardens and blocks moisture. However, due to different formulations from various PET suppliers, in recent years there have still been a number of updated research results in this field [11,12]. For the accelerated weathering testing of PET, the UVA band of UV radiation (wavelength around 340 nm) is a suitable simulator if the artificial irradiance intensity level is moderate.…”