In materials characterization, haze is often as important as color in the quality control of manufactured products. The term haze refers to the visual clarity of a material. The historical evaluation for haze was simply visual, where the operator would hold a piece of the material up to a bright light and check for cloudiness The presence of haze can either be wanted or unwanted. For example, the clear plastic panels which cover the LED’s of an instrument display are intentionally hazy. In other materials, however, the level of haze is tightly controlled, such as, for example, in the polymer sheets which are layered in between automotive glass.
A standard UV/Vis spectrophotometer fitted with an integrating sphere accessory can accurately measure haze. A % haze calculation is quite easy to perform on a Lambda UV/Vis spectrophotometer fitted with one of the Labsphere™ integrating sphere accessories
The procedure is described in the ASTM 1003-92 “Standard Method for Haze and Luminous Transmittance of Transparent Plastics” The procedure involves acquiring four transmission scans of the sample from 780 to 380 nm, each with a different configuration of the integrating sphere, integrating the area under each curve, and plugging the values into the following equation…
Haze = [(T4/T2) - (T3/T1)] x 100%
where T1 through T4 are changing configurations of the sample placement on the sphere.
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| First measurement: Background Correction T1 |
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| The Second Measurement T2 |
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| The Third Measurement T3 |
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| The Fourth Measurement T4 |
The figure below displays example spectra for these four haze component measurements made on a clear polymer sheet sample.
The areas for the entire spectral range is calculated and the data is processed in an Excel spreadsheet.
% Haze = [(T4/T2) - (T3/T1)] x 100%
= [(1940/11781) – (0.194/40000)
=[(0.1647 – 0.00000485)]
= 16.47 %
Calculation of % haze is also part of the PerkinElmer Architectural Glass Software package.
