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Title: Protective coatings and sealants for solar applications

Abstract

An aging study has been completed which evaluated a number of polymeric materials for potential use as (1) protective coatings for back surfaces of mirrors and (2) solar heliostat edge seals. These investigations were conducted in an artificial weathering chamber that accelerated thermal cycling. The primary mirror failure mode was observed to be silver corrosion resulting from moisture exposure. To increase mirror longevity in current heliostat designs, intimate bonding at all the composite interfaces is essential to minimize moisture pathways to the silvered surface. If any voids or delaminations are present, mirror degradation will eventually occur. Delaminations can also occur as the result of mechanical stresses brought about by mismatches in the various materials coefficients of thermal expansion. If good bonding cannot be achieved or mechanical stresses avoided, then improved moisture barriers must be designed to assure mirror longevity. With good adhesion, a KRATON rubber was found to exhibit superior back surface mirror protection (12 months in environmental chamber with no corrosion). An ultraviolet stabilized butyl rubber appeared to be the best edge seal. All heliostats edge sealed with silicones showed silver corrosion which indicated either poor bonding or moisture permeation.

Authors:
;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
5139922
Report Number(s):
SAND-80-0808
DOE Contract Number:  
AC04-76DP00789
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; HELIOSTATS; SEALS; MIRRORS; PROTECTIVE COATINGS; SERVICE LIFE; SOLAR REFLECTORS; AGING; FIBERGLASS; PAPER; PLASTICS; RUBBERS; SILICONES; THERMAL CYCLING; WEATHERING; COATINGS; ELASTOMERS; EQUIPMENT; ORGANIC COMPOUNDS; ORGANIC POLYMERS; PETROCHEMICALS; PETROLEUM PRODUCTS; POLYMERS; SILOXANES; SOLAR CONCENTRATORS; SOLAR EQUIPMENT; CSP; Concentrating Solar Power; 141000* - Solar Collectors & Concentrators

Citation Formats

Wischmann, K. B., and Gonzales, M. H. Protective coatings and sealants for solar applications. United States: N. p., 1980. Web. doi:10.2172/5139922.
Wischmann, K. B., & Gonzales, M. H. Protective coatings and sealants for solar applications. United States. https://doi.org/10.2172/5139922
Wischmann, K. B., and Gonzales, M. H. Mon . "Protective coatings and sealants for solar applications". United States. https://doi.org/10.2172/5139922. https://www.osti.gov/servlets/purl/5139922.
@article{osti_5139922,
title = {Protective coatings and sealants for solar applications},
author = {Wischmann, K. B. and Gonzales, M. H.},
abstractNote = {An aging study has been completed which evaluated a number of polymeric materials for potential use as (1) protective coatings for back surfaces of mirrors and (2) solar heliostat edge seals. These investigations were conducted in an artificial weathering chamber that accelerated thermal cycling. The primary mirror failure mode was observed to be silver corrosion resulting from moisture exposure. To increase mirror longevity in current heliostat designs, intimate bonding at all the composite interfaces is essential to minimize moisture pathways to the silvered surface. If any voids or delaminations are present, mirror degradation will eventually occur. Delaminations can also occur as the result of mechanical stresses brought about by mismatches in the various materials coefficients of thermal expansion. If good bonding cannot be achieved or mechanical stresses avoided, then improved moisture barriers must be designed to assure mirror longevity. With good adhesion, a KRATON rubber was found to exhibit superior back surface mirror protection (12 months in environmental chamber with no corrosion). An ultraviolet stabilized butyl rubber appeared to be the best edge seal. All heliostats edge sealed with silicones showed silver corrosion which indicated either poor bonding or moisture permeation.},
doi = {10.2172/5139922},
url = {https://www.osti.gov/biblio/5139922}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1980},
month = {9}
}