Optical properties of PV backsheets: key indicators of module performance and durability

Felder, Thomas; Gambogi, William J.; Kopchick, James G.; Peacock, R. Scott; Stika, Katherine M.; Trout, T. John; Bradley, Alexander Z.; Hamzavytehrany, Babak; Gok, Abdülkerim; French, Roger H.; Fu, Oakland; Hu, Hongjie

doi:10.1117/12.2062063

Cited by 5 publications

(6 citation statements)

References 6 publications

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“…2 ), the peak assignments are as follows (cm −1 ): 2926 and 2854 (C–H stretching) [not shown in the expanded spectra of the figure]; 1712 (C=O stretching); 1577, 1604 (aromatic C–C stretching); 1450, 1408, 1369 (C–H bending); 1257, 1240 (C=O stretching), 1173 (C–H bending); 1113, 1093 (C–O– stretching); 1016 (C–C ring bending), 956 (C–H stretching of the cyclohexylene ring); 875, 723 (aromatic C–H bending) [ 17 – 19 ]. The cleaning procedures showed similar spectra, except for ST, which demonstrated a small peak at 1670 cm −1 assigned to acid groups [ 20 ]. The curve-fit analysis of the ester peak of Clear Aligner (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The control group demonstrated approximately twice the area of the 1740 cm −1 peak in comparison with the treated groups (4 vs 2 for ST and 2.1 for RB, RC), whereas the differences in the 1690 cm −1 peak area were smaller (5.7 vs 4.1 for ST and 4.8 for RB, RC). The ST group demonstrated additionally two low wavenumber peaks (1677 and 1644 cm −1 , 5.9% in sum of tA C=O ) attributed to acid formation [ 20 ].…”

Section: Resultsmentioning

confidence: 99%

“…Although the sampling depth of the method is limited to the uppermost 2 μm zone (vs bulk characterization of ground/polished specimens by IIT), it may provide important information on the degradation mechanisms involved. Comparison of the spectra at the fingerprint range (2000–650 cm −1 ) showed a difference only in Clear Aligner treated with ST, where a peak appeared at 1699 cm −1 attributed to acid production via oxidation of the PET structure [ 20 ]. A more detailed analysis by curve-fitting of the ester peak components demonstrated the presence of free and H–bonded C=O groups at a ratio of 0.4 for RB, RC and 0.5 for CO and ST.…”

Section: Discussionmentioning

confidence: 99%

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Εffect of cleansers on the composition and mechanical properties of orthodontic aligners in vitro

et al. 2022

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Background The aim of the study was to investigate the effect of three aligner cleaners on the composition and mechanical properties of two types of orthodontic aligners. Materials and methods The cleaners tested were two alkaline peroxide solutions (Retainer Brite—RB; Retainer Cleaner—RC) and one peroxide-free (Steraligner—ST) and the aligners Clear Aligner (C, polyester) and Invisalign (I, polyester–urethane). The aligners were immersed in the cleaner solutions as instructed every day (15 min for RB, RC; 5 min for ST) for a two-week period. The acidity of the solutions was tested with a pH meter. The changes in the chemical composition of the aligners were studied by attenuated total-reflection Fourier transform infrared spectrometry (ATR-FTIR), while Instrumented Indentation Testing (IIT) was used for assessment of changes in Martens Hardness (HM), modulus (EIT), elastic index (nIT) and relaxation (RIT). Results RB and RC were weakly acidic (pH = 6.3), whereas ST was mildly acidic (pH = 4.8). The ATR-FTIR analysis demonstrated evidence of acidic hydrolysis of C in ST and I in RB. The IIT-derived properties of I were not affected by the cleaners. However, for C a significant change was found in HM (all cleaners), nIT (all cleaners) and RIT (RB, ST). Although the chemical changes support a hydrolytic material deterioration, the results of mechanical properties may interfere with the material residual stresses during fabrication. Conclusions Caution should be exerted in the selection of aligner cleaners. The mild acidic cleanser was more aggressive to the polyester, whereas an alkaline peroxide to the polyester–urethane aligner.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Εffect of cleansers on the composition and mechanical properties of orthodontic aligners in vitro

et al. 2022

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“…Extended exposure to UV radiation and moisture drive wide-spread cleavage of ester bonds in the polymer through photolytic and hydrolytic degradation mechanisms resulting in discoloration, gloss loss, hazing, decreased molecular weight, and eventual deterioration of the physical integrity of the film [8–13]. Photolysis of PET primarily occurs through the absorption of high energy, short wavelength, UV light, which leads to chain scission of chemical bonds along the polymer backbone.…”

Section: Introductionmentioning

confidence: 99%

Multivariate multiple regression models of poly(ethylene-terephthalate) film degradation under outdoor and multi-stressor accelerated weathering exposures

et al. 2018

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Developing materials for use in photovoltaic (PV) systems requires knowledge of their performance over the warranted lifetime of the PV system. Poly(ethylene-terephthalate) (PET) is a critical component of PV module backsheets due to its dielectric properties and low cost. However, PET is susceptible to environmental stressors and degrades over time. Changes in the physical properties of nine PET grades were modeled after outdoor and accelerated weathering exposures to characterize the degradation process of PET and assess the influence of stabilizing additives and weathering factors. Multivariate multiple regression (MMR) models were developed to quantify changes in color, gloss, and haze of the materials. Natural splines were used to capture the non-linear relationship between predictors and responses. Model performance was evaluated via adjusted-R2 and root mean squared error values from leave-one-out cross validation analysis. All models described over 85% of the variation in the data with low relative error. Model coefficients were used to assess the influence of weathering stressors and material additives on the property changes of films. Photodose was found to be the primary degradation stressor and moisture was found to increase the degradation rate of PET. Direct moisture contact was found to impose more stress on the material than airbone moisture (humidity). Increasing the concentration of TiO2 was found to generally decrease the degradation rate of PET and mitigate hydrolytic degradation. MMR models were compared to physics-based models and agreement was found between the two modeling approaches. Cross-correlation of accelerated exposures to outdoor exposures was achieved via determination of cross-correlation scale factors. Cross-correlation revealed that direct moisture contact is a key factor for reliable accelerated weathering testing and provided a quantitative method to determine when accelerated exposure results can be made more aggressive to better approximate outdoor exposure conditions.

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“…PET is highly susceptible to moisture and ultraviolet (UV) irradiance [ 9 ]. PET degradation mainly occurs via photolytic and hydrolytic cleavage of an ester bond resulting in decreased molecular weight with concomitant changes in crystallinity, morphology, discoloration (yellowing) and/or haze formation.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Accelerated weathering exposures were performed on poly(ethylene-terephthalate) (PET) films. Longitudinal multi-level predictive models as a function of PET grades and exposure types were developed for the change in yellowness index (YI) and haze (%). Exposures with similar change in YI were modeled using a linear fixed-effects modeling approach. Due to the complex nature of haze formation, measurement uncertainty, and the differences in the samples’ responses, the change in haze (%) depended on individual samples’ responses and a linear mixed-effects modeling approach was used. When compared to fixed-effects models, the addition of random effects in the haze formation models significantly increased the variance explained. For both modeling approaches, diagnostic plots confirmed independence and homogeneity with normally distributed residual errors. Predictive R2 values for true prediction error and predictive power of the models demonstrated that the models were not subject to over-fitting. These models enable prediction under pre-defined exposure conditions for a given exposure time (or photo-dosage in case of UV light exposure). PET degradation under cyclic exposures combining UV light and condensing humidity is caused by photolytic and hydrolytic mechanisms causing yellowing and haze formation. Quantitative knowledge of these degradation pathways enable cross-correlation of these lab-based exposures with real-world conditions for service life prediction.

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Optical properties of PV backsheets: key indicators of module performance and durability

Cited by 5 publications

References 6 publications

Εffect of cleansers on the composition and mechanical properties of orthodontic aligners in vitro

Εffect of cleansers on the composition and mechanical properties of orthodontic aligners in vitro

Multivariate multiple regression models of poly(ethylene-terephthalate) film degradation under outdoor and multi-stressor accelerated weathering exposures

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

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