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Effect of IR transparency of the top polymer layer on low thermal IR emittance paint coatings
Author(s) -
Ma ChenChi M.,
Ho WenDar
Publication year - 1999
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11555
Subject(s) - materials science , coating , thermal emittance , polymer , layer (electronics) , composite material , natural rubber , substrate (aquarium) , attenuation coefficient , polymer substrate , diffuse reflection , absorption (acoustics) , alkyd , optics , beam (structure) , oceanography , physics , geology
Abstract A two‐layer model was developed to accurately represent low thermal IR emittance paint coatings. The coatings were formed by mixing aluminum flakes with polymeric binders. Because of the different densities of these two components, a two‐layer structure was constructed with a pure polymeric layer on top and an in‐homogeneous layer underneath. The absorption properties of the top polymeric layer hinder the IR reflectance of the coating. This two‐layer model was used to quantitatively determine how IR transparency of the top polymer layer influences the reflectance of the coating. The bottom layer was considered to be a substrate with a specific diffuse reflectance, and the ray tracing method was used to calculate the reflectance of this polymer‐coated, diffusing substrate system. The reflectance of the coating with a low absorption coefficient (0.01 μm −1 ) top polymer (3 μm thick) was reduced 50% compared with when a high absorption coefficient (0.1 μm −1 ) top polymer was used. Measurements of coatings of chlorinated rubber and alkyd rubber on a diffuse gold substrate confirmed the reliability of the model predictions.