Temporal evolution and pathway models of poly(ethylene-terephthalate) degradation under multi-factor accelerated weathering exposures

Abstract

Photolytic and hydrolytic degradation of poly(ethylene-terephthalate) (PET) polymers with different stabilizers were performed under multiple accelerated weathering exposures and changes in the polymers were monitored by various evaluation techniques. Yellowing was caused by photolytic degradation and haze formation was induced by combined effects of photolytic and hydrolytic degradation. The formation of light absorbing chromophores and bleaching of the UV stabilizer additive were recorded through optical spectroscopy. Chain scission and crystallization were found to be common mechanisms under both photolytic and hydrolytic conditions, based on the infrared absorption of the carbonyl ( C = O ) band and the trans ethylene glycol unit, respectively. The degradation mechanisms determined from these evaluations were then used to construct a set of degradation pathway network models using the network structural equation modeling (netSEM) approach. This method captured the temporal evolution of degradation by assessing statistically significant relationships between applied stressors, mechanistic variables, and performance level responses. Quantitative pathway equations provided the contributions from mechanistic variables to the response changes.

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.…”

“…This requires reliable laboratory-accelerated weathering procedures that estimate durability under specific exposure conditions as well as good lifetime models that yield good estimates of service lifetimes from weathering data [ 492 ]. However, acceleration of photo-damage in the laboratory has to ensure that wavelengths and intensities of radiation used, attain the same degradative mechanisms as solar exposure [ 489 , 493 ].…”

Predictive models of poly(ethylene-terephthalate) film degradation under multi-factor accelerated weathering exposures

“…% UV stabilizer with a chemical formula of C 22 H 12 N 2 O 4 (a benzoxazinone type UV stabilizer commercialized under the name of Cyasorb UV 3638 by CYTEC). Although no additive was found in the hydrolytically stabilized grade, the stabilization was achieved by deactivating reactive carboxyl end groups (CEG) [40]. See S1 Appendix for details.…”

Degradation Mechanism Detection in Photovoltaic Backsheets by Fully Convolutional Neural Network

“…Such an automated way to identify degradation mechanism would reduce the operation and maintenance of PV farms and provide insights into the degradation mechanisms of fielded backsheets. More importantly, a large amount of data collected and annotated during operation would accelerate the rate of establishing a reliable relationship between various environmental conditions and degradation rates of materials 10,16,17 .…”