Solar Energy Materials & Solar Cells 90 (2006) 1208–1219 Structure–infrared optical property-correlations of polar ethylene copolymer films for solar applications G. Oreski à , G.M. Wallner Polymer Competence Center Leoben GmbH, Parkstr. 11, Institute of Materials Science and Testing of Plastics, University of Leoben, Franz-Josef-Str. 18, A-8700 Leoben, Austria Received 11 May 2005; accepted 11 July 2005 Available online 22 August 2005 Abstract In this paper, an understanding of the physical relationships between the material structure and the infrared optical properties of polar ethylene homo and copolymers for solar applications is described. The infrared optical properties are relevant for the heat transport of transparent insulation structures based on these materials. To establish structure–property- correlations molecular structure parameters such as comonomer content and the concentra- tion of carbon–oxygen single bond and carbon–hydroxyl groups, respectively, were determined. For 50 mm thick films a good correlation between the concentration of the functional carbon–hydroxyl and the carbon–oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. The carbon–hydroxyl group appears to be slightly more effective than the carbon–oxygen single bond. r 2005 Elsevier B.V. All rights reserved. Keywords: Polyethylene copolymer; Infrared optical properties; Transparent insulation; Polymer film 1. Introduction Polymeric materials are already used for many different solar energy-related components. Concerning solar thermal systems plastics play a decisive role as ARTICLE IN PRESS www.elsevier.com/locate/solmat 0927-0248/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.solmat.2005.07.005 à Corresponding author. Fax: +43 3842 429 626. E-mail address: oreski@pccl.at (G. Oreski).