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Title: Development of Damp-Heat Resistant Self-Primed EVA and Non-EVA Encapsulant Formulations at NREL

Abstract

Self-primed ethylene-vinyl acetate (EVA) and non-EVA (PMG) encapsulant formulations were developed that have greater resistance to damp heat exposure at 85 deg C and 85% relative humidity (RH) (in terms of adhesion strength to glass substrates) than a commonly used commercial EVA product. The self-primed EVA formulations were developed on the basis of high-performing glass priming formulations that have previously proven to significantly enhance the adhesion strength of unprimed and primed EVA films on glass substrates during damp heat exposure. The PMG encapsulant formulations were based on an ethylene-methylacrylate copolymer containing glycidyl methacrylate.

Authors:
;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
882814
Report Number(s):
NREL/CP-520-38984
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Conference
Resource Relation:
Related Information: Presented at the 2005 DOE Solar Energy Technologies Program Review Meeting held November 7-10, 2005 in Denver, Colorado. Also included in the proceedings available on CD-ROM (DOE/GO-1020060-2245; NREL/CD-520-38577)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; PHOTOVOLTAICS; SOLAR; ETHYLENE-VINYL ACETATE; EVA; PV; NREL; Solar Energy - Photovoltaics

Citation Formats

Pern, F. J., and Jorgensen, G. J.. Development of Damp-Heat Resistant Self-Primed EVA and Non-EVA Encapsulant Formulations at NREL. United States: N. p., 2005. Web.
Pern, F. J., & Jorgensen, G. J.. Development of Damp-Heat Resistant Self-Primed EVA and Non-EVA Encapsulant Formulations at NREL. United States.
Pern, F. J., and Jorgensen, G. J.. Tue . "Development of Damp-Heat Resistant Self-Primed EVA and Non-EVA Encapsulant Formulations at NREL". United States. doi:. https://www.osti.gov/servlets/purl/882814.
@article{osti_882814,
title = {Development of Damp-Heat Resistant Self-Primed EVA and Non-EVA Encapsulant Formulations at NREL},
author = {Pern, F. J. and Jorgensen, G. J.},
abstractNote = {Self-primed ethylene-vinyl acetate (EVA) and non-EVA (PMG) encapsulant formulations were developed that have greater resistance to damp heat exposure at 85 deg C and 85% relative humidity (RH) (in terms of adhesion strength to glass substrates) than a commonly used commercial EVA product. The self-primed EVA formulations were developed on the basis of high-performing glass priming formulations that have previously proven to significantly enhance the adhesion strength of unprimed and primed EVA films on glass substrates during damp heat exposure. The PMG encapsulant formulations were based on an ethylene-methylacrylate copolymer containing glycidyl methacrylate.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 01 00:00:00 EST 2005},
month = {Tue Nov 01 00:00:00 EST 2005}
}

Conference:
Other availability
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  • We investigated the effectiveness of glass-surface priming to promote enhanced adhesion of EVA laminates during damp-heat exposure at 85 C and 85% relative humidity. The primary objective was to develop advanced encapsulant formulations by incorporation of various primer formulations that exhibit improved adhesion during damp-heat exposure. Several primer formulations were identified that greatly enhanced the EVA adhesion strength, including to the extent that peeling could not be initiated, even for the laminates of the glass substrate/fast-cure EVA15295P/TPE backsheet (a Tedlar/polyester/EVA tri-laminate) that were exposed in a damp-heat test chamber for more than 750 h. The results show that a synergisticmore » increase in the interfacial hydrophobicity, siloxane density, and cross-linking density are the key attributes to the improvement in the EVA adhesion strength.« less
  • Presented at the 2001 NCPV Program Review Meeting: We have developed several new ethylene-vinyl acetate (EVA) formulations modified on the basis of NREL patented EVA formulations [1]. The new formulations can be cured to a desired gel content of {approx}80% in the ambient at temperatures 20-30 C lower than the typical conditions in vacuum (i.e. {approx}150 C). Glass/glass laminates showed transmittance spectra that are essentially the same as that of EVA 15295P in the visible and NIR regions but higher in the UV region. Results of fluorescence analysis of the ambient-processed new EVA formulations showed the concentrations of the curing-generatedmore » {alpha},{beta}-unsaturated carbonyl chromophores, which are responsible for the UV induced EVA discoloration and photodegradation, were considerably lower than that of EVA 15295P, therefore suggesting a better photochemical stability of new EVA formulations.« less
  • Several new formulations of ethylene vinyl acetate (EVA)-based encapsulant have been developed at NREL and have greatly improved photostability against UV-induced discoloration. The new EVA formulations use stabilizers and a curing agent entirely different from any of those used in existing formulations known to the authors. No discoloration was observed for the laminated and cured samples that were exposed to a {approximately}5-sun UV light (300--400 nm) from a solar simulator at a black panel temperature (BPT) of 44 {+-} 2 C for {approximately}3250 h followed by at 85 C for {approximately}850 h, an equivalent of approximately 9.4 years for anmore » average 6-h daily, 1-sun solar exposure in Golden, Colorado. Under the same conditions, substantial discoloration and premature delamination were observed for two commercial EVA formulations. Encapsulation with the new EVA formulations should extend the long-term stability for PV modules in the field, especially when coupled with UV-filtering, Ce-containing glass superstrates.« less
  • We review in chronological order the research stages and fundamental concepts involved in developing modified and new EVA formulations for improved performance against photo-induced degradation and discoloration. The new NREL EVA formulations use additives totally different from the present commercial formulations (EVA A9918 and EVA 15295). Validation of their long-term photostability and thermostability is presently under way. Together with UV-absorbing glass superstrates, they may offer better success in achieving a more reliable module performance and longer service life without significant EVA discoloration problems, which are commonly experienced with EVA A9918 and, at a lesser rate, EVA 15295. {copyright} {ital 1997more » American Institute of Physics.}« less
  • A survey of case histories of EVA-based encapsulant discoloration in fielded modules in the U. S. reveals that the problem is limited to areas of the West and Southwest that have comparatively high solar insolation and ambient temperature. There have been no reported cases of discolored EVA encapsulant from modules fielded in the Northeast, Central U. S., or Western Europe. The absence of hard data regarding module operating temperatures, solar insolation, onset of discoloration, and quantitative information regarding the degree of discoloration has made correlation between various fabrication, placement, and operating conditions and incidence of discoloration difficult it not impossible.more » However, the degree of discoloration does appear to correlate with increasing average daily direct normal solar radiation and approximate maximum module operating temperature, as estimated from maximum ambient temperatures. It is clear that the discoloration problem is not limited to the modules of any one manufacturer, however, the rate and degree of discoloration do appear to vary from company to company. Also, discoloration is not limited to EVA encapsulant sheet from any one supplier.« less