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Research Papers

Damp Heat Aging Behavior of a Polyamide-Based Backsheet for Photovoltaic Modules

[+] Author and Article Information
Klaus J. Geretschläger

Institute of Polymeric Materials and Testing,
Johannes Kepler University Linz,
Altenberger Straße 69,
Linz 4040, Austria
e-mail: klaus_jakob.geretschlaeger@jku.at

Gernot M. Wallner

Institute of Polymeric Materials and Testing,
Johannes Kepler University Linz,
Altenberger Straße 69,
Linz 4040, Austria
e-mail: gernot.wallner@jku.at

Ingrid Hintersteiner

Institute of Analytical Chemistry,
Johannes Kepler University Linz,
Altenberger Straße 69,
Linz 4040, Austria
e-mail: ingrid.hintersteiner@tiger-coatings.com

Wolfgang Buchberger

Institute of Analytical Chemistry,
Johannes Kepler University Linz,
Altenberger Straße 69,
Linz 4040, Austria
e-mail: wolfgang.buchberger@jku.at

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received November 25, 2015; final manuscript received March 4, 2016; published online April 5, 2016. Assoc. Editor: Alison Lennon.

J. Sol. Energy Eng 138(4), 041003 (Apr 05, 2016) (5 pages) Paper No: SOL-15-1398; doi: 10.1115/1.4032977 History: Received November 25, 2015; Revised March 04, 2016

This paper describes and evaluates accelerated aging of a titanium dioxide (TiO2) filled polyamide (PA) based backsheet film for photovoltaic (PV) modules. Damp heat exposure (85%RH, 85 °C) was carried out up to 2000 hrs. The backsheet was characterized using microscopic, spectroscopic, thermoanalytic, chromatographic, and mechanical methods. While Raman microscopy, infrared spectroscopy in attenuated total reflection mode (IR-ATR), scanning calorimetry (DSC), and thermal gravimetric analysis did not reveal aging-induced changes, significant yellowing was detected by ultraviolet visible near infrared (UV/VIS/NIR) spectroscopy. Depending on the stabilizer type (UV-absorbers, hindered amine light stabilizers (HALSs), and antioxidants), rather different consumption rates were ascertained by high-performance liquid chromatography (HPLC) and gas chromatography (GC). Although the ultimate mechanical properties decreased significantly, no full embrittlement was obtained after damp heat exposure of up to 2000 hrs. The observed physical and chemical aging mechanisms were classified as within the induction period without premature failure.

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Figures

Grahic Jump Location
Fig. 1

Representative DSC curves for the unaged (solid lines) and the 2000 hrs aged (dashed lines) material

Grahic Jump Location
Fig. 2

Structural formulas of the quantified stabilizers Tinuvin 234, Tinuvin 770, ADK AO 80, and Irganox 1010

Grahic Jump Location
Fig. 3

Concentration of Tinuvin 234, Tinuvin 770, ADK AO 80, and Irganox 1010 as function of damp heat exposure time

Grahic Jump Location
Fig. 4

Normal-hemispheric UV/VIS/NIR reflectance spectra describing damp heat aging-related optical changes

Grahic Jump Location
Fig. 5

Human perception of backsheet color expressed by the CIE 1931 chromaticity diagram using red, green, and blue chromaticity coordinates

Grahic Jump Location
Fig. 6

Derived yellowness (YIASTM D1925), whiteness (WIASTM E313), and tint indices (TASTM E313) describing film discoloration as a function of damp heat exposure time

Grahic Jump Location
Fig. 7

Progress of mechanical properties

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