Specular transmittance, optical properties

Kynar and Tedlar (PVF3 and PVF) nearly met the desired specular transmittance and showed little or no optical and mechanical degradation after the equivalent of 16 years exposure. Metallzed polyesters and polycarbonates met initial optical and mechanical requirements but showed severe property degradation after relatively short environmental exposure. 

The principles and standard procedures used in the determination of color can be found in ASTM E308. Equipment is conunercially available for measuring optical properties of polymers for these purposes. Major suppliers include Gardner (gloss meter for specular gloss, haze meter for haze and luminous transmittance, and clarity meter for specular transmission) and Hunter Lab (spectrocolorimeter). 

Light Transmittance (luminous transmittance, light transmissivity) The ability of a material to pass incident light through it, whether specular or diffuse. ASTM (www.astm.org) prescribes several tests of this property in plastics. Transmissivity is the ratio of the intensity of the transmitted light to that of the unreflected incident light. See also Opacity. (Fox AM (2001) Optical properties of solids. Oxford University Press, UK)... 

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